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SPELTHORNE BOROUGH COUNCIL LOCAL PLAN

Strategic Highway Assessment Part 2: Results and Analysis

Spelthorne Borough Council Local Plan Strategic Highway Assessment Part 2: Results and Analysis

Project Title: Spelthorne Borough Council Local Plan

Document Title: Strategic Highway Assessment Part 2: Results and Analysis

Date: 11/10/19

Prepared By: Samuel Pink

Authorised By: William Bryans

All maps contained in this document are licensed © Crown copyright and database rights 2018 Ordnance Survey 100019613 and are orientated to grid north

Amendment List Iss. / Amendment List Rev.

0201SF10 07/08/02 Filename: S:\Project-current\3000 PROJECT NOS STARTING WTIH 3000\3613\53613T52_Spelthorne_2019\02_Reports

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Spelthorne Borough Council Local Plan Strategic Highway Assessment Part 2: Results and Analysis

CONTENTS 1 INTRODUCTION ...... 6

1.1 REGULATION 18 APPRAISAL ...... 6 1.2 ORGANISATION OF THIS REPORT ...... 6 2 RESULTS AND ANALYSIS ...... 7

2.1 OVERVIEW ...... 7 2.2 SCENARIO OVERVIEW ...... 7 2.3 SELECT LINK ANALYSIS ...... 11 2.4 LEVEL OF SERVICE (LOS) METRIC ...... 19 2.5 LINK ANALYSIS ...... 19 2.6 INCREASE IN JUNCTION DELAY ...... 30 2.7 THE STRATEGIC HIGHWAY NETWORK ...... 43 2.8 CROSS BOUNDARY IMPACTS ...... 58 2.9 NETWORK HOTSPOTS AND MITIGATION ...... 69 3 OVERVIEW OF FINDINGS ...... 72

3.2 KEY POINTS ...... 72

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TABLE OF FIGURES

FIGURE 2-1 AM PEAK HOUR TOTAL VEHICLE-KILOMETRES PER SCENARIO FOR SPELTHORNE BOROUGH ...... 8 FIGURE 2-2 PM PEAK HOUR TOTAL VEHICLE-KILOMETRES PER SCENARIO FOR SPELTHORNE BOROUGH ...... 8 FIGURE 2-3 AM PEAK HOUR TOTAL VEHICLE-HOURS PER SCENARIO FOR SPELTHORNE BOROUGH ...... 9 FIGURE 2-4 PM PEAK HOUR TOTAL VEHICLE-HOURS PER SCENARIO FOR SPELTHORNE BOROUGH ...... 9 FIGURE 2-5 AM PEAK HOUR AVERAGE LINK SPEED FOR SPELTHORNE BOROUGH ...... 10 FIGURE 2-6 PM PEAK HOUR AVERAGE LINK SPEED FOR SPELTHORNE BOROUGH ...... 10 FIGURE 2-7 SCENARIO C SELECT LINK ANALYSIS OF LAND OFF WORPLE ROAD, WORPLE ROAD (256 DWELLINGS)...... 14 FIGURE 2-8 SCENARIO C SELECT LINK ANALYSIS OF LAND TO SOUTH AND WEST OF STRATTON ROAD, STRATTON ROAD (245 DWELLINGS)...... 15 FIGURE 2-9 SCENARIO C SELECT LINK ANALYSIS OF LAND TO SOUTH OF ASHFORD COMMON WATER TREATMENT WORKS, CHARLTON ROAD (200 DWELLINGS)...... 16 FIGURE 2-10 SCENARIO D SELECT LINK ANALYSIS OF KEMPTON PARK (3,000 DWELLINGS)...... 17 FIGURE 2-11 LINK FLOW DIFFERENCE PLOTS, SCENARIO B COMPARED WITH SCENARIO A ...... 21 FIGURE 2-12 LINK FLOW DIFFERENCE PLOTS, SCENARIO C COMPARED WITH SCENARIO A ...... 22 FIGURE 2-13 LINK FLOW DIFFERENCE PLOTS, SCENARIO D COMPARED WITH SCENARIO A ...... 23 FIGURE 2-14: LINK FLOW DIFFERENCE PLOTS BETWEEN SCENARIOS A AND D AT KEMPTON PARK...... 25 FIGURE 2-15 LINK LEVEL OF SERVICE FOR SCENARIO A AM AND PM PEAK HOUR ...... 27 FIGURE 2-16: AM PEAK HOUR LOS SCENARIO A VS SCENARIO D ...... 28 FIGURE 2-17: PM PEAK HOUR LOS SCENARIO A VS SCENARIO D ...... 29 FIGURE 2-18: DELAY IN SECONDS PER VEHICLE AT JUNCTIONS WITHIN THE BOROUGH WITH A LOS VALUE OF C – D DURING THE DO MINIMUM SCENARIO A...... 30 FIGURE 2-19 M25 JUNCTION 13 FLOW DIFFERENCE PLOT BETWEEN SCENARIO B AND SCENARIO A FOR BOTH THE AM AND PM PEAK HOURS...... 45 FIGURE 2-20 M25 JUNCTION 13 FLOW DIFFERENCE PLOT BETWEEN SCENARIO C AND SCENARIO A FOR BOTH THE AM AND PM PEAK HOURS...... 46 FIGURE 2-21 M25 JUNCTION 13 FLOW DIFFERENCE PLOT BETWEEN SCENARIO D AND SCENARIO A FOR BOTH THE AM AND PM PEAK HOURS...... 47 FIGURE 2-22 A30 FLOW DIFFERENCE PLOT OF SCENARIO B VS SCENARIO A FOR BOTH THE AM AND PM PEAK HOURS.WITH AN INSERT SHOWING THE CROOKED BILLET ROUDABOUT...... 48 FIGURE 2-23 A30 FLOW DIFFERENCE PLOT OF SCENARIO C VS SCENARIO A FOR BOTH THE AM AND PM PEAK HOURS WITH AN INSERT SHOWING THE CROOKED BILLET ROUNDABOUT...... 49 FIGURE 2-24 A30 FLOW DIFFERENCE PLOT OF SCENARIO D VS SCENARIO A FOR BOTH THE AM AND PM PEAK HOURS WITH AN INSERT SHOWING THE CROOKED BILLET ROUNDABOUT...... 50 FIGURE 2-25 M3 FLOW DIFFERENCE PLOT OF SCENARIO B VS SCENARIO A FOR BOTH THE AM AND PM PEAK HOURS WITH AN INSERT SHOWING THE SUNBURY CROSS ROUNDABOUT...... 51 FIGURE 2-26 M3 FLOW DIFFERENCE PLOT OF SCENARIO C VS SCENARIO A FOR BOTH THE AM AND PM PEAK HOURS WITH AN INSERT SHOWING THE SUNBURY CROSS ROUNDABOUT...... 52 FIGURE 2-27: M3 FLOW DIFFERENCE PLOT OF SCENARIO D VS SCENARIO A FOR BOTH THE AM AND PM PEAK HOURS WITH AN INSERT SHOWING THE SUNBURY CROSS ROUNDABOUT...... 53

TABLE OF TABLES

TABLE 2-1 VEHICLE TRIP MATRIX TOTALS BY SCENARIO WITH DIFFERENCES FROM SCENARIO A...... 7 TABLE 2-2 INTERPRETATION OF LEVEL OF SERVICE CATEGORIES ...... 19 TABLE 2-3: DO MINIMUM SCENARIO A AM PEAK HOUR JUNCTIONS CLASSIFIED AS LOS C – D ...... 32 TABLE 2-4: DO MINIMUM SCENARIO A PM PEAK HOUR JUNCTIONS CLASSIFIED AS LOS C – D ...... 35 TABLE 2-5: SCENARIO B VS SCENARIO A JUNCTION PERFORMANCE DURING THE AM ASSESSED HOUR. JUNCTIONS WITH A DETERIORATION TO LOS C/D AND/OR INCREASED JUNCTION DELAY OF >1 SECOND...... 37 TABLE 2-6: SCENARIO B VS SCENARIO A JUNCTION PERFORMANCE DURING THE PM ASSESSED HOUR. JUNCTIONS WITH A DETERIORATION TO LOS C/D AND/OR INCREASED JUNCTION DELAY OF >1 SECOND...... 37 TABLE 2-7: SCENARIO C VS SCENARIO A JUNCTION PERFORMANCE DURING THE AM ASSESSED HOUR. JUNCTIONS WITH A DETERIORATION TO LOS C/D AND/OR INCREASED JUNCTION DELAY OF >1 SECOND...... 38

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TABLE 2-8: SCENARIO C VS SCENARIO A JUNCTION PERFORMANCE DURING THE PM ASSESSED HOUR. JUNCTIONS WITH A DETERIORATION TO LOS C/D AND/OR INCREASED JUNCTION DELAY OF >1 SECOND...... 39 TABLE 2-9: SCENARIO D VS SCENARIO A JUNCTION PERFORMANCE DURING THE AM ASSESSED HOUR. JUNCTIONS WITH A DETERIORATION TO LOS C/D AND/OR INCREASED JUNCTION DELAY OF >1 SECOND...... 40 TABLE 2-10: SCENARIO D VS SCENARIO A JUNCTION PERFORMANCE DURING THE PM ASSESSED HOUR. JUNCTIONS WITH A DETERIORATION TO LOS C/D AND/OR INCREASED JUNCTION DELAY OF >1 SECOND...... 41 TABLE 2-11 TRAFFIC FLOW SUMMARY IN PCU FOR THE M25 FOR THE AM PEAK HOUR (0800 – 0900)...... 54 TABLE 2-12 TRAFFIC FLOW SUMMARY IN PCU FOR THE M25 FOR THE PM PEAK HOUR (1700 – 1800) ...... 56 TABLE 2-13 MERGE DELAY (SECONDS PER VEHICLE) FOR THE AM AND PM PEAK HOUR ...... 58 TABLE 2-14 AM PEAK HOUR TRAFFIC FLOW SUMMARY FOR A PRINCIPAL AND B ROADS WHICH ENTER THE SPELTHORNE BOUNDARY FROM NEIGHBOURING AUTHORITIES ...... 60 TABLE 2-15 AM PEAK HOUR TRAFFIC FLOW SUMMARY FOR A PRINCIPAL AND B ROADS WHICH EXIT THE SPELTHORNE BOUNDARY INTO NEIGHBOURING AUTHORITIES ...... 62 TABLE 2-16 PM PEAK HOUR TRAFFIC FLOW SUMMARY FOR A PRINCIPAL AND B ROADS WHICH ENTER THE SPELTHORNE BOUNDARY FROM NEIGHBOURING AUTHORITIES ...... 64 TABLE 2-17 PM PEAK HOUR TRAFFIC FLOW SUMMARY FOR A PRINCIPAL AND B ROADS WHICH EXIT THE SPELTHORNE BOUNDARY INTO NEIGHBOURING AUTHORITIES ...... 66 TABLE 2-18: APEX CORNER AM PEAK HOUR DO MINIMUM SCENARIO A VS SCENARIO D PROPOSED KEMPTON PARK DEVELOPMENT ...... 67 TABLE 2-19: APEX CORNER PM PEAK HOUR DO MINIMUM SCENARIO A VS SCENARIO D PROPOSED KEMPTON PARK DEVELOPMENT ...... 68 TABLE 2-20 AM PEAK HOUR NETWORK HOTSPOTS (*THOSE MARKED WITH AN ASTERISK MEAN LOS IS LESS THAN CATEGORY C IN THE DO MINIMUM SCENARIO A AND HAS SUBSEQUENTLY DETERIORATED)...... 70 TABLE 2-21 PM PEAK HOUR NETWORK HOTSPOTS (*THOSE MARKED WITH AN ASTERISK MEAN LOS IS LESS THAN CATEGORY C IN THE DO MINIMUM SCENARIO A AND HAS SUBSEQUENTLY DETERIORATED)...... 71

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1 INTRODUCTION

1.1 Regulation 18 Appraisal

Spelthorne Borough Council is in the process of developing their 2035 Local Plan to ensure future growth can be accommodated within the borough. Surrey County Council have been commissioned to assess the potential impact of the development options using the County’s strategic transport model SINTRAM.

The overall aim is to help inform the decision making surrounding the suitability of potential development sites which have been identified, and to highlight junctions and sections of roads on which to focus mitigation solutions. This will aid the Borough Council by providing the transport evidence base to inform the Regulation 181 consultation.

The purpose of this report is to undertake a comparison of potential strategic sites to assist Spelthorne Borough Council in identifying which sites to bring forward as part of their emerging Local Plan.

1.2 Organisation of this Report

The Strategic Highway Assessment (SHA) Report is split into two parts: - Part 1 details the technical aspects of the modelling work undertaken, which include model development, validation and forecasting; and - Part 2 provides the results and analysis of the forecasts, together with an overview of the key findings from the modelling.

Within this Part 2, Chapter 2 describes the results and analysis of this Strategic Highway Assessment (SHA). This includes a comparison of link flows and junction delay, as well as an evaluation of any cross boundary and motorway and trunk road impacts.

Chapter 3 concludes by summarising the Strategic Highway Assessment (SHA) and highlighting the main points which have arisen.

NOTE: The figures and tables in this report are designed for viewing in print and at standard scales, but they have a resolution that enables them to be viewed on- screen with a reasonable level of zoom to facilitate reading and discerning details. All figures are orientated to grid north.

1 As set out in the Town and Country Planning (Local Planning) Regulations 2012

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2 RESULTS AND ANALYSIS

2.1 Overview

The presented results represent modelled forecast traffic impacts on highways for the forecast year 2035 taken from the Local Model, for the four scenarios: - Scenario A: Do Minimum. This scenario includes all background growth as well as committed developments identified from the base year (since 2014) to the forecast year 2035, where committed developments comprise sites already built, or in the process of construction, or have planning permission.

- Scenario B: Growth Option 1. As Scenario A plus sites most likely to be developed by the future year (including potential urban site allocations and SLAA sites).

- Scenario C: Growth Option 2. As Scenario B, also includes potential green belt site allocations.

- Scenario D: Kempton Park Bespoke Scenario. As Scenario B, also includes the proposed development at Kempton Park, instead of the greenbelt site allocation identified in Scenario C.

Within all of the scenarios, natural demographic and employment changes, as determined by the Department for Transport’s (DfT) National Trip End Model (NTEM) have been included. In line with the DfT’s Transport Appraisal Guidance, adjustments have been made to the NTEM data to reflect the locality and composition of the committed and non-committed development sites which comprise these scenarios.

To determine the highway impacts of the options, Scenarios B to D are compared with the Do Minimum Scenario A.

Unless stated, the results are for Spelthorne Borough. Specific analysis with regards to impacts on the motorway and trunk road network is presented in Section 2.7, and cross boundary impacts follows in Section 2.8.

2.2 Scenario Overview

The matrix totals for all vehicles (car, LGV and HGV) are presented in Table 2-1. As expected, Scenario A has the least total trips and Scenario D the most. The total number of vehicle trips in the Borough in Scenario D increases by 1.5% in the AM peak hour, and 2.1% in the PM peak hour, compared to Scenario A.

Table 2-1 Vehicle Trip Matrix Totals by Scenario with Differences from Scenario A

AM Peak Hour (0800 – 0900) PM Peak Hour (1700 – 1800) Scenario Vehicles Difference % Vehicles per Difference % per Hour from SA Change Hour from SA Change A 123,273 - - 102,528 - - B 123,391 118 0.1% 102,692 164 0.2% C 124,097 824 0.8% 103,426 898 0.9% D 125,096 1823 1.5% 104,703 2175 2.1%

The total vehicle distance is presented in Figure 2-1 for the AM peak hour and Figure 2-2 for the PM peak hour. Similarly, total vehicle travel time is presented in Figure 2-3 and Figure 2-4, and average speed in Figure 2-5 and Figure 2-6, for the AM and PM peak hours respectively.

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It is worth noting that these average speeds are for the whole assessed area of Spelthorne Borough. These average speeds are therefore relatively high due to the proportion of vehicles travelling on higher speed roads (e.g., M25, M3, A30 etc.) through the area.

Total vehicle distance and travel time are greater in the AM peak hour than the PM peak hour, across all scenarios. This shows that the AM peak hour is more congested, which is typical as peak commuting and education escort trips coincide.

It can be seen that in both the AM and PM peak hours total vehicle distance and total vehicle time increases with each scenario. All Local Plan Growth Option Scenarios have greater impacts when compared with the Do Minimum Scenario A.

Figure 2-1 AM Peak Hour Total Vehicle-Kilometres per Scenario for Spelthorne Borough

Figure 2-2 PM Peak Hour Total Vehicle-Kilometres per Scenario for Spelthorne Borough

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Figure 2-3 AM Peak Hour Total Vehicle-Hours per Scenario for Spelthorne Borough

Figure 2-4 PM Peak Hour Total Vehicle-Hours per Scenario for Spelthorne Borough

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Figure 2-5 AM Peak Hour Average Link Speed for Spelthorne Borough

Figure 2-6 PM Peak Hour Average Link Speed for Spelthorne Borough

Scenario B

The amount of traffic on the network increases slightly with only a moderate impact on network performance. During the AM peak, the total traffic increases only by 0.2% vehicle kilometres, and total delay increases by 0.59% vehicle hours resulting in a marginal drop in average speeds across the network. The largest increase in traffic is on A roads which gain 229 vehicle kilometres (0.46%).

Scenario B is subject to only a small number of trips being added to the network, with increases of only 118 trips (0.09%) in the AM peak and 164 trips (0.15%) in the PM peak. The reason behind this seemingly slight increase in trips between scenarios A and B is the change in land use. Many of the development sites in Scenario B make use of existing commercial land use. Replacing these with

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residential land uses results in less trips as residential developments tend to generate fewer trips.

In addition, residential developments tend to generate less traffic compared with commercial developments, traffic being the number of vehicles coupled with the distance they travel.

During the PM peak, the total traffic increases by only 0.33% vehicle kilometres, and total delay increases by 0.6% vehicle hours resulting in a marginal drop in average speeds across the network. The largest increase in traffic again is on A roads which increase by 273 vehicle kilometres (0.62%).

Scenario C

During the AM peak, the total traffic increases by 1.37% vehicle kilometres and total delay increases by 2.97% vehicle hours. These changes result in a marginal drop in average speeds across the network. The largest increase in traffic is on minor roads which gain 1,030 vehicle kilometres (3.65%).

During the PM peak, the total traffic increases by 1.73% vehicle kilometres and total delay increases by 3.24% vehicle hours. Again, these changes result in a drop in average speeds across the network. The largest increase in traffic is on minor roads which increase by 1,220 vehicle kilometres (5.37%).

Scenario D

During the AM peak, the total traffic increases by 2.3% vehicle kilometres and total delay increases by 5.47% vehicle hours resulting in a drop in average speeds across the network. The largest increase in traffic is on motorways which gain 2,036 vehicle kilometres (1.77%).

During the PM peak, the total traffic increases by 2.51% vehicle kilometres and total delay increases by 6.22% vehicle hours resulting in a drop in average speeds across the network. The largest increase in traffic is on motorways which gain 1,646 vehicle kilometres (1.7%).

Both scenarios C and D show that in congested areas any increase in traffic has a disproportionate effect on delay, thereby having a greater impact on journey times and traffic speeds.

2.3 Select Link Analysis

To help visualise and understand the highway impact of the largest sites being evaluated, select link analysis has been undertaken. Within Scenario C, the difference from Scenario B is the greenfield site allocations, as such, of these sites, those with more than 150 proposed residential units have been evaluated. These are listed below: - Land off Worple Road, Worple Road (256 dwellings) shown in Figure 2-7

- Land to South and West of Stratton Road, Stratton Road (245 dwellings) shown in Figure 2-8; and

- Land to South of Ashford Common Water Treatment Works, Charlton Road (200 dwellings) shown in Figure 2-9.

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Furthermore, in Scenario D the difference from Scenario B is the proposed Kempton Park development site (3,000 dwellings). Therefore, select link analysis has been undertaken on this site in Figure 2-10.

Select link plots show the routing of vehicles accessing and egressing these development sites. In the listed figures, only values greater than 10 PCU per hour per direction have been labelled, with the exception of Kempton Park (Figure 2-10) where only values of greater than 50 PCU per hour have been labelled; the geographical context has not been limited to Spelthorne Borough in this section.

When interpreting the select link plots for specific development sites it should be noted that the results presented are for highway modes of car, LGV and HGV only and the single AM and PM peak hours. This is to say that a greater amount of trips are generated from each development site than presented in Figure 2-7 to Figure 2-10. Consequently it should also be recognised that high levels of highway congestion can impact the modal choice of trips between highway or public transport modes.

For consistency of analysis Figure 2-7 to Figure 2-10 present vehicle flows for the single AM and PM peak hours and highway users of car, LGV and HGV.

Figure 2-7 presents the routing of vehicle trips (PCU) to and from the Land off Worple Road, Worple Road site. It can be seen that in both the AM and the PM peak hours vehicles predominantly route to/from Staines towards the M25 along the B376 and along the A308. Some vehicles go towards the east via residential roads to the A308 at Fordbridge. In the PM, there are also some vehicles routing to/from the north on Worple Road and Kingston Road.

The routing of vehicles to and from the Land to south and west of Stratton Road site is shown in Figure 2-8. The pattern in the AM and PM is very similar. Vehicles disperse from the site fairly evenly to the east through Sunbury Cross roundabout and onto the A316, also to the south on the A244. Slightly less vehicles route along the A244 north to the A308 to the west.

Figure 2-9 shows the routing of vehicles to and from the Land to South of Ashford Common Water Treatment Works site. To the north vehicles route to the A308 to Sunbury Cross roundabout and then onto the A316. To the south, vehicles take the A244 towards Upper Halliford, while some head south-east towards Littleton and the B376.

Figure 2-10 presents the routing associated with the Kempton Park site. In the AM, the majority exit Kempton Park to the west along the A308 to Sunbury Cross roundabout, from here most go along the M3 west, some continuing west on the M3 and some joining the M25 both Anticlockwise and Clockwise, of those going Clockwise, several route along the A318 towards Brooklands. Also, from Sunbury Cross roundabout, traffic routes north-east on the A316 towards Twickenham, and other traffic routes along the A308 towards Staines or the A244 towards Heathrow. In the other direction, to the east of Kempton Park, the rest of the traffic travels along the A308 towards Kingston or Thames Ditton as well as along Fordbridge Road to Walton-on-Thames. In the PM, the distribution of the trips routing to/from Kempton Park follows a very similar pattern to the AM. However, there are more trips on the A308 both east and west. There are also more trips on the B375 from the south- west. Meanwhile, the M3 and M25 both have less trips than the AM.

There appears to be some re-routing occurring in the proposed Kempton Park Scenario D. Notably, during the AM peak hour there is a large amount of trips

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heading westbound on the M3 which originate from the development. However, during the PM peak hour there is a large amount of trips accessing the development from the A308 westbound. Traffic heading eastbound on the M3 during the PM peak hour seems to be exiting to the south of Kempton Park on the A3050 and Fordbridge Road. Re-routing does not seem to sufficiently explain these changes in flows between the peak hours and further analysis would be required in order to provide a better insight.

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Figure 2-7 Scenario C Select Link analysis of Land off Worple Road, Worple Road (256 dwellings).

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Figure 2-8 Scenario C Select Link analysis of Land to South and West of Stratton Road, Stratton Road (245 dwellings).

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Figure 2-9 Scenario C Select Link analysis of Land to South of Ashford Common Water Treatment Works, Charlton Road (200 dwellings).

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Figure 2-10 Scenario D Select Link analysis of Kempton Park (3,000 dwellings).

AMPM PeakPeak HourHour (0800(1700 –– 0900)1800)

AM Peak Hour (0800 – 0900)

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PM Peak Hour (1700 – 1800)

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2.4 Level of Service (LoS) Metric

The Level of Service (LoS) metric, which is an adaptation of the US Highway Capacity Manual LoS metric, is determined by the level of traffic flows relative to network link and junction capacities, expressed in terms of the ratio of flow to capacity (RFC). The interpretation of RFC values in terms of experienced levels of congestion are described in Table 2-2.

A level of service categorised as A represents the best operating conditions with an RFC value of less than 0.5. On the other hand, category D is the worst level of service with an RFC value greater than 1. An RFC value greater than 1 means that the stretch of road or turning movement has a higher level of traffic flow than its theoretical capacity, suggesting flow breakdown and extensive queues.

Table 2-2 Interpretation of Level of Service Categories

Category Description RFC A Free flow Traffic flows at or above the posted speed limit and motorists have complete mobility between lanes. Motorists have a high 0 to 0.5 level of physical and psychological comfort. B Stable flow Ability to manoeuvre through lanes is noticeably restricted and lane changes require more driver awareness. Speeds slightly decrease as traffic volume slightly increase. Freedom to 0.5 to 0.85 manoeuvre within the traffic stream is much more limited and driver comfort levels decrease. Roads remain safely below but efficiently close to capacity. C Unstable Flow becomes irregular and speed varies rapidly because flow, there are virtually no usable gaps to manoeuvre in the traffic operating at stream and speeds rarely reach the posted limit. Any disruption 0.85 to 1 capacity to traffic flow, such as merging ramp traffic or lane changes, will create a shock wave affecting traffic upstream. Drivers' level of comfort become poor. D Forced or Every vehicle moves in lockstep with the vehicle in front of it, breakdown with frequent slowing required. Travel time cannot be >1 of flow predicted, with generally more demand than capacity.

The methodology for calculating the LoS has been applied to the analysis of both link flow and junction delay to aid the interpretation of the model results. The calculated LoS has been colour coded using the traffic light colours: green; amber; and red, as shown in Table 2-2 above.

2.5 Link Analysis

Section 2.3 shows how the vehicle flows associated with the largest development sites would disperse on the road network. In this section, the actual cumulative impact this causes on the road links in the network has been examined.

Flow difference plots for Spelthorne Borough have been presented for Scenarios B to D, in comparison with Scenario A for the weekday AM and PM peak hours in Figure 2-11 to Figure 2-13. Bandwidths coloured red show an increase in flow, whereas those coloured blue represent a decrease in flow, with their size being proportional to the increase or decrease.

Figure 2-11 presents the difference in flow between scenarios A and B. Scenario B contains developments already granted planning permission along with sites most likely to be granted planning permission by 2035. The largest increases in flow are centred on the main routes around Staines and Ashford, especially during the PM.

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Figure 2-12 shows the difference in flow between scenarios A and C. Scenario C is the same as Scenario B with the addition of potential Green Belt site allocations.

Figure 2-13 illustrates the impact the potential development of Kempton Park would have on the network.

As expected the largest increases in link flows are found and on the main roads and around the new development sites throughout the Borough.

The blue bandwidths show a decrease in flow when comparing scenarios. This can sometimes be due to residential development replacing commercial land uses which generally have more vehicle trips during the analysed time periods. However, re- routing is also an effect of local congestion. Spelthorne Borough is congested, and even small changes in local congestion cause trips to change their routes to avoid the delay.

In Scenario B, as shown in Figure 2-11, the largest increase in flow during the AM peak hour is located on both the eastbound and westbound sections of the A30 between M25 Junction 13 and the Crooked Billet roundabout. Increased trips on the eastbound section of this road coincide with a decrease in eastbound trips on the B376 into Staines. As stated previously, this is an impact of re-routing generated by small changes in local congestion. This is not surprising as many of the proposed Scenario B developments are located in the Staines area. The A3044 southbound has a reduced flow with trips re-routing to the M25 southbound. During the PM peak hour the roads which incur the largest increases in flow are the A30, A3044, A308, B378, B377 and Kingston Road (in Staines).

Figure 2-12 indicates that the changes in traffic flows in the Borough for Scenario C when compared to the Do Minimum Scenario A are similar to that in Scenario B, but by an increased magnitude. This is due to Scenario C including potential Green Belt site allocations as well as all proposed developments contained within Scenario B. During the AM peak hour, the most notable increases in flow from Scenario B to Scenario C occur on the B376. During the PM peak hour there are notable increases in flow on the A308 eastbound, A244 northbound, New Road and Charlton Road near Littleton.

Figure 2-13 presents the differences in flow in Scenario D compared to the Do Minimum Scenario A. In both time periods the trends shown are very similar to that of Scenario C in the majority of the Borough. Although there are much larger differences in the east since this is the vicinity of the large Kempton Park development which is the focus of Scenario D.

As is expected, during the PM peak hour, increases in vehicle flow are greatest in Scenario D.

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Figure 2-11 Link Flow Difference Plots, Scenario B Compared with Scenario A

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Figure 2-12 Link Flow Difference Plots, Scenario C Compared with Scenario A

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Figure 2-13 Link Flow Difference Plots, Scenario D Compared with Scenario A

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Comparison of network summary statistics and flow difference plots for Scenarios A and D highlight the potential impact of the proposed Kempton Park development which is estimated to generate over 1,705 vehicle trips in the AM and 2,011 in the PM. As a result, some of the largest increases in flow are focussed in the Sunbury area around Kempton Park.

Figure 2-14 shows a closer look at the flow difference between Scenario A and D in the Kempton Park area.

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Figure 2-14: Link flow difference plots between Scenarios A and D at Kempton Park.

During both the AM and the PM assessed periods there are major increases in flow as a result of additional trips associated with the Kempton Park development. Additional trips in Scenario D join the network at the present access points to Kempton Park in the absence of further information.

Figure 2-15 presents the level of service (LoS) of all roads within the borough for the AM and PM peak hours respectively for the Do Minimum Scenario A. Bandwidths

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are coloured as in Table 2-2: green for free flow and stable flow (LoS A and B); orange for unstable flow, operating at capacity (LoS C); and red for forced or breakdown of flow (LoS D).

It can be seen that for the majority of the Borough, the capacity of the roads is adequate for the volume of carried traffic, with a LoS of either A or B coloured green. This may be surprising, given the level of congestion which already exists within the area, but it is the junctions which mostly inhibit traffic flow. The roads which are shown to have either a LoS category of C or D, which are operating at or above capacity in all scenarios, are as follows:

- M25 Junction 13 – 14 Clockwise; - M25 Junction 14 – 13 Anticlockwise; - B376 Laleham Road northbound (AM only); - B377 Ashford Road eastbound approach to Fordbridge Roundabout (AM and PM peak hours); - B377 Fordbridge Road westbound approach to Fordbridge Roundabout (AM peak only); - A30 westbound approach to Crooked Billet (AM peak only); - A308 Staines Road East westbound towards Sunbury Cross Roundabout (AM and PM peak hours); - A244 Walton Bride Road between Walton Lane (roundabout) and A3050 Oatlands Drive, both directions (AM and PM peak hours); and - A244 Walton Bridge Road between Walton Lane and Marshall’s Roundabout southbound (AM and PM Peak hours).

In Scenarios B and C, there is very little deterioration on roads to a LoS of C or D, when compared with the Do Minimum Scenario A. However in Scenario D there is deterioration of LoS (B to D) on the westbound approach to the Sunbury Cross roundabout during the AM peak hour. There is also a deterioration of LoS (B to C) on the A308 Hampton Court Road during the PM peak hour. LoS deterioration for Scenario D in the Kempton Park area is illustrated in both Figure 2-16 and Figure 2-17.

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Figure 2-15 Link Level of Service for Scenario A AM and PM peak hour

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Figure 2-16: AM Peak hour LoS Scenario A vs Scenario D

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Figure 2-17: PM Peak hour LoS Scenario A vs Scenario D

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2.6 Increase in Junction Delay

Figure 2-18 illustrates the junction delay of those junctions in the Do Minimum Scenario A which are modelled as having a LoS value of C or higher during both assessed time periods. The diameter of the circle relates to the magnitude of delay

The Level of Service at junctions is determined by the level of traffic flows relative to the junction capacities, expressed in terms of the ratio of flow to capacity (RFC) as described in Section 2.4. Junctions are defined as in Table 2-2: Free flow and stable flow (LoS A and B); unstable flow, operating at capacity (LoS C); and Forced or breakdown of flow (LoS D).

Figure 2-18: Delay in seconds per vehicle at junctions within the Borough with a LoS value of C – D during the Do Minimum Scenario A.

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Table 2-3 and Table 2-4 present the junctions illustrated in Figure 2-18 along with junction type and description.

Table 2-5 and Table 2-6 present junction delay comparisons for Scenario B vs Scenario A. In order to present only the most useful information, only junctions with an increase delay of >1 second and/or a deterioration in LoS to C or D are presented.

Junctions which experience an increased delay of >1 second and/or a deterioration in LoS to C or D in Scenario C vs Scenario A are presented in Table 2-7 and Table 2-8.

Junctions which experience an increased delay of >1 second and/or a deterioration in LoS to C or D in Scenario D vs Scenario A are presented in Table 2-9 and Table 2-10.

In some instances LoS deteriorates between scenarios, yet junction delay marginally improves. This indicates that the worst performing arm at the junction in question has improved, but the total flow weighted delay for the entire junction has increased.

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Table 2-3: Do Minimum Scenario A AM peak hour junctions classified as LoS C – D

Delay in seconds per Performance vehicle Node id Name Junction Type Do-Minimum AM pk Do-Minimum RFC Do-Minimum LOS A308 Staines Road West signalised 231398 Signalised 48 0.88 C crossroads with A244 Windmill Road 223695 A30 and B378 signalised Bulldog Junction Signalised 38 0.88 C A308 Staines Road West signalised 231210 crossroads with B378 School Road / Signalised 38 0.85 C Ashford Road A244 Windmill Road signalised crossroads 230851 with International Way and Brooklands Signalised 37 0.85 C Close A308 Staines Road signalised crossroads 231238 Signalised 35 0.86 C with Littleton Lane and Chertsey Road A244 Chertsey Road signalised junction 231592 Signalised 34 0.85 C with Chertsey Road A3044 Stanwell Moor Road signalised 224093 Signalised 33 0.85 C junction with B378 Park Road B378 School Road / Convent Road 223591 signalised crossroads with Feltham Hill Signalised 29 0.85 C Road A308 Staines Bridge Road signalised 223116 Signalised 25 0.85 C junction with B376 Hale Street Charlton Lane priority junction with New 230575 Give Way 25 0.97 C Road and Charlton Road Southern Perimeter Road signalised 224513 Signalised 25 0.85 C junction with Seaford Road A308 Staines Road West signalised 231415 Signalised 23 0.85 C junction with Escort Road

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Delay in seconds per Performance vehicle Node id Name Junction Type Do-Minimum AM pk Do-Minimum RFC Do-Minimum LOS A244 Walton Bridge Road roundabout 228423 Roundabout 22 0.96 C with Walton Lane B376 Laleham Road / Green Road 228330 signalised crossroads with High Street / Signalised 22 0.85 C Old Charlton Road A308 Staines Road East approach to 230885 signalised junction at Sunbury Cross Signalised 21 0.85 C roundabout A244 Upper Halliford Bypass signalised 230570 Signalised 20 0.85 C junction with Charlton Lane A244 Windmill Road signalised crossroads 230843 Signalised 20 0.85 C with Dolphin Road and Windmill Road W B376 Laleham Road signalised junction 222703 Signalised 19 0.85 C with Watersplash Road A308 Thames Street signalised junction 421001 Signalised 19 0.85 C with B376 Laleham Road A308 South Street signalised junction with 223150 Signalised 18 0.85 C Mustard Mill Road M3 eastbound off slip signalised approach 230878 Signalised 17 0.85 C to the Sunbury Cross roundabout B376 Wraysbury Road signalised junction 223122 Signalised 17 0.85 C with Hale Street Vicarage Road southbound approach to 231488 Signalised 16 0.85 C the signalised Sunbury Cross roundabout A308 London Road signalised junction with 223285 Signalised 16 0.85 C Fairfield Avenue A308 London Road signalised junction with 223208 Signalised 15 0.85 C Kingston Road

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Delay in seconds per Performance vehicle Node id Name Junction Type Do-Minimum AM pk Do-Minimum RFC Do-Minimum LOS A308 High Street signalised junction with 223207 Signalised 12 0.85 C Fairfield Avenue B377 Kingston Road eastbound approach 223467 Give Way 10 0.86 C to the Fordbridge roundabout A244 Walton Bridge Road priority junction 228424 Give Way 10 1.06 D with Walton Lane

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Table 2-4: Do Minimum Scenario A PM peak hour junctions classified as LoS C – D

Delay in seconds per Performance vehicle Node id Name Junction Type Do-Minimum AM pk Do-Minimum RFC Do-Minimum LOS A244 Windmill Road signalised crossroads 230851 with International Way and Brooklands Signalised 38 0.85 C Close A308 Staines Road West signalised 231398 Signalised 38 0.86 C crossroads with A244 Windmill Road A308 Staines Road signalised crossroads 231238 Signalised 36 0.85 C with Littleton Lane and Chertsey Road A308 Staines Road West signalised 231210 crossroads with B378 School Road / Signalised 34 0.85 C Ashford Road 223695 A30 and B378 signalised Bulldog Junction Signalised 33 0.85 C B376 Wraysbury Road signalised junction 223122 Signalised 32 0.85 C with Hale Street A244 Chertsey Road signalised junction 231592 Signalised 31 0.85 C with Chertsey Road B378 School Road / Convent Road 223591 signalised crossroads with Feltham Hill Signalised 30 0.85 C Road A3044 Stanwell Moor Road signalised 224093 Signalised 29 0.85 C junction with B378 Park Road A308 Staines Bridge Road signalised 223116 Signalised 28 0.85 C junction with B376 Hale Street Southern Perimeter Road signalised 224513 Signalised 25 0.85 C junction with Seaford Road A308 Thames Street signalised junction 421001 Signalised 24 0.85 C with B376 Laleham Road

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Delay in seconds per Performance vehicle Node id Name Junction Type Do-Minimum AM pk Do-Minimum RFC Do-Minimum LOS A308 Thames Street signalised priority 449166 junction with Elmsleigh Road shopping Signalised 22 0.85 C centre A244 Walton Bridge Road roundabout 228423 Roundabout 21 0.96 C with Walton Lane M25 clockwise off slip signalised approach 223908 Signalised 20 0.85 C to Junction 13 A244 Windmill Road signalised crossroads 230843 Signalised 20 0.85 C with Dolphin Road and Windmill Road W A308 South Street signalised junction with 223150 Signalised 19 0.85 C Mustard Mill Road A3044 Stanwell Moor Road northbound 224142 approach to roundabout with A3113 Give Way 18 0.90 C Airport Way Kingston Road signalised junction with 223431 Signalised 17 0.85 C Woodthorpe Road A244 Upper Halliford Bypass signalised 230570 Signalised 17 0.85 C junction with Charlton Lane Green Street northbound approach to 230879 Signalised 17 0.85 C signalised Sunbury Cross roundabout Vicarage Road southbound approach to 231488 Signalised 16 0.85 C the signalised Sunbury Cross roundabout A308 London Road signalised junction with 223208 Signalised 15 0.85 C Kingston Road A244 Walton Bridge Road priority junction 228424 Give Way 4 0.87 C with Walton Lane

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Table 2-5: Scenario B vs Scenario A junction performance during the AM assessed hour. Junctions with a deterioration to LoS C/D and/or increased junction delay of >1 second.

Delay in seconds per vehicle Performance Junction Node id Name Do- Do- Do- Type Minimum SB AM pk Difference Minimum Minimum AM pk AM RFC SB AM RFC LOS SB AM LoS B376 Wraysbury Road signalised 223122 Signalised 17 32 15 0.85 0.85 C C junction with Hale Street A30 Staines bypass signalised 223909 Signalised 17 18 0.3 0.849 0.85 B C approach to the M25 J13 A308 Thames Street signalised 449166 junction with Elmsleigh Road Signalised 23 23 0.0 0.849 0.85 B C shopping centre M25 clockwise off slip signalised 223908 Signalised 20 20 -0.1 0.849 0.85 B C approach to Junction 13

Table 2-6: Scenario B vs Scenario A junction performance during the PM assessed hour. Junctions with a deterioration to LoS C/D and/or increased junction delay of >1 second.

Delay in seconds per vehicle Performance Junction Node id Name Do- Do- Do- Type Minimum SB AM pk Difference Minimum Minimum AM pk AM RFC SB AM RFC LOS SB AM LoS Hanworth Road right turn only 231502 into Hanworth Road Give Way 2 3 1 0.06 0.05 A A

A308 London Road signalised 223285 junction with Fairfield Avenue Signalised 15 16 1 0.849 0.85 B C

A308 Staines Road West 231415 signalised junction with Escort Signalised 23 23 0.01 0.849 0.85 B C Road

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Table 2-7: Scenario C vs Scenario A junction performance during the AM assessed hour. Junctions with a deterioration to LoS C/D and/or increased junction delay of >1 second.

Delay in seconds per vehicle Performance

Do- Node id Name Junction Type SC AM Do- Do- Minimum Difference pk Minimum SC AM Minimum SC AM pk AM RFC RFC LOS LoS 223122 B376 Wraysbury Road signalised junction with Hale Street Signalised 17 32 15 0.85 0.85 C C 230575 Charlton Lane priority junction with New Road and Charlton Road Give Way 25 32 7 0.97 0.98 C C 228423 A244 Walton Bridge Road roundabout with Walton Lane Roundabout 22 25 3 0.96 0.98 C C B377 Kingston Road eastbound approach to the Fordbridge 223467 Give Way 10 13 3 0.86 0.91 C C roundabout 230779 Stratton Road priority junction with Nursery Road Give Way 1 2 1 0.14 0.13 A A Green Street northbound approach to signalised Sunbury Cross 230879 Signalised 16 16 0.1 0.849 0.85 B C roundabout 223908 M25 clockwise off slip signalised approach to Junction 13 Signalised 20 20 -0.1 0.849 0.85 B C

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Table 2-8: Scenario C vs Scenario A junction performance during the PM assessed hour. Junctions with a deterioration to LoS C/D and/or increased junction delay of >1 second.

Delay in seconds per vehicle Performance Do- Node id Name Junction Type SC PM Do- Do- Minimum Difference pk Minimum SC PM Minimum SC AM pk PM RFC pk LOS LoS 228423 A244 Walton Bridge Road roundabout with Walton Lane Roundabout 21 26 5 0.96 0.98 C C A3044 Stanwell Moor Road northbound approach to roundabout 224142 Give Way 18 20 1 0.90 0.91 C C with A3113 Airport Way 223285 A308 London Road signalised priority junction with Fairfield Avenue Signalised 15 17 1 0.849 0.85 B C 231502 Hanworth Road right turn only into Hanworth Road Give Way 2 3 1 0.06 0.05 A A 222703 B376 Laleham Road signalised junction with Watersplash Road Signalised 11 12 1 0.69 0.74 B B A308 Staines Road East approach to signalised junction at Sunbury 230885 Signalised 18 18 0.2 0.849 0.85 B C Cross roundabout 224598 Horton Road eastbound signalised approach to M25 J14 Signalised 17 17 -0.01 0.849 0.85 B C 231415 A308 Staines Road West signalised junction with Escort Road Signalised 23 23 -0.1 0.849 0.85 B C

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Table 2-9: Scenario D vs Scenario A junction performance during the AM assessed hour. Junctions with a deterioration to LoS C/D and/or increased junction delay of >1 second.

Node Name Junction Delay in seconds per vehicle Performance id Type Do- SD Differenc Do- SD Do- SD Minimu AM e Minimu AM Minimu LoS m AM pk pk m AM RFC m LOS RFC 22312 B376 Wraysbury Road signalised junction with Hale Street Signalised 17 32 15

2 0.85 0.85 C C 22842 A244 Walton Bridge Road roundabout with Walton Lane Roundabou 22 33 10

3 t 0.96 1.00 C C 23057 Charlton Lane priority junction with New Road and Charlton Road Give Way 25 29 5

5 0.97 0.98 C C 23088 M3 westbound off slip signalised approach to the Sunbury Cross Signalised 16 19 3

8 roundabout 0.81 0.83 B B 23149 Hanworth Road giveway to M3 westbound approach to Sunbury Give Way 1 3 2

1 Cross roundabout 0.27 0.36 A A 22346 B377 Kingston Road eastbound approach to the Fordbridge Give Way 10 13 2

7 roundabout 0.86 0.90 C C 23090 Downside priority junction with Green Street Give Way 2 4 2

0 0.39 0.66 A B 23081 Green Street priority junction with Manor Lane Give Way 4 6 2

8 0.15 0.28 A A 23075 A244 Upper Halliford Road signalised junction with Nursery Road Signalised 21 23 2

7 0.79 0.80 B B 23139 A308 Staines Road West signalised crossroads with A244 Signalised 48 49 1

8 Windmill Road 0.88 0.88 C C 22343 Kingston Road signalised junction with Woodthorpe Road Signalised 17 17

1 0.04 0.85 0.85 B C 44916 A308 Thames Street signalised junction with Elmsleigh Road Signalised 23 23

6 shopping centre -0.03 0.85 0.85 B C

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Table 2-10: Scenario D vs Scenario A junction performance during the PM assessed hour. Junctions with a deterioration to LoS C/D and/or increased junction delay of >1 second.

Node Name Junction Delay in seconds per vehicle Performance id Type Do- SD Differenc Do- SD Do- SD Minimu PM e Minimu PM Minimu LO m PM pk pk m PM RFC m LOS S RFC 22842 A244 Walton Bridge Road roundabout with Walton Lane Roundabou 21 58 38

3 t 0.96 1.04 C D 23139 A308 Staines Road West signalised crossroads with A244 Signalised 38 42 4

8 Windmill Road 0.86 0.85 C C 41000 A308 Staines Road East priority junction with Kempton Park Gate Give Way 1 3 2

6 6 0.40 0.45 A A 23146 A308 Staines Road West signalised approach to Sunbury Cross Signalised 14 17 2

3 roundabout 0.73 0.80 B B 23075 A244 Upper Halliford Road signalised junction with Nursery Road Signalised 20 21 2

7 0.80 0.82 B B 23111 A308 Staines Road East priority junction with Broomfield Give Way 1 3 2

5 0.46 0.69 A B 23088 M3 westbound off slip signalised approach to the Sunbury Cross Signalised 13 14 1

8 roundabout 0.62 0.73 B B 23150 Hanworth Road right turn only into Hanworth Road Give Way 2 3 1

2 0.06 0.05 A A 23087 M3 eastbound off slip signalised approach to the Sunbury Cross Signalised 14 15 1

8 roundabout 0.79 0.82 B B 23088 A308 Staines Road East approach to signalised junction at Signalised 18 18

5 Sunbury Cross roundabout 0.32 0.85 0.85 B C 22459 Horton Road eastbound signalised approach to M25 J14 Signalised 17 17

8 0.02 0.85 0.85 B C 23141 A308 Staines Road West signalised junction with Escort Road Signalised 23 22 -1

5 0.85 0.85 B C

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Do Minimum Scenario A

Notably the junctions with particularly large delay values are present in all scenarios, and have been shown to be operating over or near capacity, with a LoS category of C or D, in all scenarios too. As a result, existing congestion highlighted in the Do Minimum Scenario A (Table 2-3 and Table 2-4) is exacerbated, thus causing a reduction in driver comfort levels and increased stress due to further deterioration of traffic conditions at such junctions.

The junction with the highest delay per vehicle and a LoS categorisation of C or above is the A308 Staines Road West signalised crossroads with A244 Windmill Road. As this junction has been highlighted for its high delay per vehicle closer analysis of the surrounding area revealed trips re-routing via Cedar Way as a means of accessing the A308 westbound and bypassing the aforementioned signals.

This re-routing occurs in each of the four scenarios. As such, this potential ‘rat run’ may require monitoring. It seems as though Cedar Way has been engineered in a manner that would suggest this is a problem that has been previously identified and actioned against.

Trips diverting onto Cedar Way may result in the A308 Staines Road West signalised crossroads with A244 Windmill Road junction delay and LoS categorisation being underestimated. In any case, the model currently suggests a LoS of C and a delay of up to 48 seconds per vehicle in the AM peak hour of the Do Minimum Scenario A and the junction will therefore be sensitive to any additional trips as a result of proposed development.

The priority junction of the A244 Walton Bridge Road and Walton Lane has a LoS categorisation of D during the AM peak hour, which is maintained for all scenarios. This is associated with the route between the A3050 Oatlands Drive and Walton Lane Roundabout also having a LoS categorisation of D.

Scenario B

Table 2-5 and Table 2-6 indicate that there will be few significant changes to vehicle delay. The largest increase in junction delay is an increased 15 seconds per vehicle at the B376 Wraysbury Road signalised junction with Hale Street during the AM peak hour, however a LoS of C is maintained for all scenarios. The increased junction delay here seems to be associated with nearby proposed developments in Scenario B and is therefore maintained in each of the three do something scenarios.

The combination of the potential development sites together with committed development means that for any junction which is close to capacity, a small amount of additional traffic may tip the balance resulting in a deterioration in performance. This additional traffic may be related to development or be comprised of existing traffic re-routing as a result of traffic generated by potential development sites. This seems to be the case with both the A308 Staines Road West signalised junction with Escort Road, and the A308 London Road signalised junction, as the RFC in the Do Minimum Scenario A was already close to being classed as LoS C.

Scenario C

The largest increase in junction delay is 15 seconds per vehicle at the B376 Wraysbury Road signalised junction with Hale Street during the AM assessed hour. A LoS of C is maintained at this junction in each of the four scenarios. The increased

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delay at this junction may be a result of trips generated by developments associated with Scenario C using the network at Staines as illustrated in Figure 2-7.

There is an increased delay of 5 seconds per vehicle on the A244 Walton Bridge Road roundabout with Walton Lane during the PM assessed hour. This junction has a maintained LoS of C in Scenario C. There is an increase in flow on the A244 Walton Bridge Road associated with Scenario C developments.

Scenario D

The A244 Walton Bridge Road roundabout with Walton Lane has an increased junction delay of 15 seconds and 38 seconds per vehicle in the AM and PM peak hours respectively. The LoS is maintained at C during the AM peak hour, however, deteriorates to a LoS of D in the PM peak hour.

During the AM peak hour junctions near the Sunbury Cross roundabout have increased delay associated with the proposed Kempton Park development. The M3 westbound off slip signalised approach delay increases by 3 seconds per vehicle. This results in a delay increase of 2 seconds per vehicle at the Hanworth Road give way to the M3 westbound off slip.

During the PM peak hour four of the approaches to the Sunbury Cross roundabout experience an increased junction delay of greater than one second. These are:

- A308 Staines Road West signalised approach (+2 seconds junction delay per vehicle); - M3 westbound off slip signalised approach (+1 seconds junction delay per vehicle); - M3 eastbound off slip signalised approach (+1 seconds junction delay per vehicle); and - A308 Staines Road east signalised approach (+0.3 seconds junction delay per vehicle). Despite only having a slight increase in delay this junction deteriorates to a LoS of C in this scenario.

The increases in junction delay in the vicinity of the Sunbury Cross roundabout are relatively small in comparison with the flows generated by the proposed Kempton Park development. This may be suggesting that existing trips are re-routing as the area gets busier.

2.7 The Strategic Highway Network

Spelthorne Borough includes several roads which are the responsibility of Highways England:

a) The M25 motorway junctions 13 to 14;

b) The M3 junctions 1 to 2;

c) The A30 from Junction 13 of the M25 to the Clockhouse Roundabout; and

d) The A316 (only for a short distance eastbound beyond the M3 J1).

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Whilst Figure 2-11 to Figure 2-13 illustrate the difference in flow for the entire Spelthorne Borough network, this section reports results for the strategic highway separately with a closer look at Highway England managed junctions.

Figure 2-19 and Figure 2-27 visually present the traffic flow for Highways England’s network contained within the subarea model, for the weekday AM and PM peak hours per scenario. Bandwidths coloured red show an increase in flow, whereas those coloured blue represent a decrease in flow, with their size being proportional to the increase or decrease. Table 2-11 and Table 2-12 present the same information but allow for easier comparison between scenarios.

Compared with the Do-Minimum Scenario A, the largest absolute increase in M25 flow is on the clockwise Junction 13 to Junction 14 mainline, in the AM peak hour in Scenario D. However, this increase is only 54 PCU which is minor relative to the total flow thus relating to a 0.6% increase. The level of service is C, corresponding to unstable flow, but this is maintained in each of the four scenarios.

Compared with the Do-Minimum Scenario A the largest percentage increase in M25 flow is 5.2% which is found on the Junction 14 off slip in the clockwise direction during the PM peak hour in Scenario C. The respective LoS for the Junction 14 clockwise off slip is A, corresponding to free flow, which is maintained for all four scenarios.

Compared with the Do-Minimum Scenario A, the largest absolute increase in A30 flow is on the eastbound stretch between the Bulldog Junction (A30 and B378 intersection) and the Crooked Billet roundabout during the AM peak hour in Scenario C. This increase amounts to an additional 5.6% flow on this section of the A30. Consequently this is also the section of the A30 with the largest percentage increase in any of the assessed scenarios. The LoS of the A30 westbound approach to the Crooked Billet roundabout is maintained at C, corresponding to unstable flow, for all four scenarios.

The largest absolute impact on the motorway network occurs in Scenario D during the PM peak hour. Compared with the Do-Minimum Scenario A there are an additional 392 PCUs using the on slip from the M3 Junction 1 (Sunbury Cross Roundabout). This 56.6% increase in flow is associated with additional trips generated by the proposed Kempton Park development.

The westbound off slip immediate approach to the Sunbury Cross roundabout is deemed as having a LoS of D which is maintained during both AM and PM assessed hours and during all four scenarios.

There are multiple small reductions in flow in comparison to Do Minimum Scenario A on the motorway network in both time periods. Intuitively, one would question why the addition of development would lead to a decrease in trips, however, congestion can cause trips to switch routes, as discussed previously in this section, with all resulting changes being proportionally small.

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Figure 2-19 M25 Junction 13 flow difference plot between Scenario B and Scenario A for both the AM and PM peak hours.

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Figure 2-20 M25 Junction 13 flow difference plot between Scenario C and Scenario A for both the AM and PM peak hours.

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Figure 2-21 M25 Junction 13 flow difference plot between Scenario D and Scenario A for both the AM and PM peak hours.

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Figure 2-22 A30 flow difference plot of Scenario B vs Scenario A for both the AM and PM peak hours.with an insert showing the Crooked Billet Roudabout.

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Figure 2-23 A30 flow difference plot of Scenario C vs Scenario A for both the AM and PM peak hours with an insert showing the Crooked Billet Roundabout.

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Figure 2-24 A30 flow difference plot of Scenario D vs Scenario A for both the AM and PM peak hours with an insert showing the Crooked Billet Roundabout.

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Figure 2-25 M3 flow difference plot of Scenario B vs Scenario A for both the AM and PM peak hours with an insert showing the Sunbury Cross Roundabout.

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Figure 2-26 M3 flow difference plot of Scenario C vs Scenario A for both the AM and PM peak hours with an insert showing the Sunbury Cross Roundabout.

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Figure 2-27: M3 flow difference plot of Scenario D vs Scenario A for both the AM and PM peak hours with an insert showing the Sunbury Cross Roundabout.

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Table 2-11 Traffic Flow Summary in PCU for the M25 for the AM Peak Hour (0800 – 0900).

Flow Difference from SA % Change from SA Link ID Road SA SB SC SD SB SC SD SB SC SD M25 Anticlockwise 77477_2 J14 on slip 776 787 804 802 11 28 26 1.4% 3.6% 3.4% M25 J14 to J13 70572_1 8,425 8,435 8,451 8,450 10 26 25 0.1% 0.3% 0.3% mainline 77427_2 M25 J13 off slip 1,403 1,411 1,410 1,408 8 7 5 0.6% 0.5% 0.4% 121339_1 M25 J13 on slip 1,318 1,337 1,333 1,286 19 15 -32 1.4% 1.1% -2.4% M25 J13 to J12 335270_2 8,339 8,360 8,374 8,328 21 35 -11 0.3% 0.4% -0.1% mainline M25 Clockwise M25 J12 to J13 77347_2 8,168 8,166 8,184 8,221 -2 16 53 0.0% 0.2% 0.6% mainline 121338_1 M25 J13 off slip 742 740 747 760 -2 5 18 -0.3% 0.7% 2.4% 90692_1 M25 J13 on slip 980 986 1,002 1,000 6 22 20 0.6% 2.2% 2.0% M25 J13 to J14 70573_2 8,406 8,412 8,439 8,460 6 33 54 0.1% 0.4% 0.6% mainline 269598_2 M25 J14 off slip 783 782 786 779 -1 3 -4 -0.1% 0.4% -0.5% 323637_2 M25 J14 on slip 999 1,005 1,000 1,010 6 1 11 0.6% 0.1% 1.1% A30 Eastbound M25 J14 to 70565_2 Crooked Billet 1,218 1,234 1,240 1,245 16 22 27 1.3% 1.8% 2.2% roundabout Crooked Billet Roundabout to 319358_2 956 966 974 985 10 18 29 1.0% 1.9% 3.0% Bulldog Junction Bulldog Junction 77458_1 towards 1,098 1,129 1,154 1,151 31 56 53 2.8% 5.1% 4.8% Clockhouse Rounabout A30 Westbound Clockhouse Roundabout to 402940_1 1,112 1,119 1,118 1,126 7 6 14 0.6% 0.5% 1.3% Bulldog Junction

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Flow Difference from SA % Change from SA Link ID Road SA SB SC SD SB SC SD SB SC SD Bulldog Junction to 77411_2 1,159 1,160 1,156 1,167 1 -3 8 0.1% -0.3% 0.7% Crooked Billet Roundabout Crooked Billet 70564_1 Roundabout to 1,722 1,746 1,755 1,742 24 33 20 1.4% 1.9% 1.2% M25 J14 M3 Eastbound M3 J2 to J1 335933_1 3,070 3,059 3,061 3,074 -11 -9 4 -0.4% -0.3% 0.1% mainline 77854_1 M3 J1 off slip 608 600 604 618 -8 -4 10 -1.3% -0.7% 1.6% 77888_1 M3 J1 on slip 902 914 933 960 12 31 58 1.3% 3.4% 6.4% M3 J1 to A316 91959_1 3,364 3,373 3,390 3,417 9 26 53 0.3% 0.8% 1.6% mainline M3 Westbound A316 to M3 J1 254742 3,753 3,717 3,738 3,781 -36 -15 28 -1.0% -0.4% 0.7% mainline 77889_2 M3 J1 off slip 797 798 792 717 1 -5 -80 0.1% -0.6% -10.0% 77857_2 M3 J1 on slip 813 818 847 1,053 5 34 240 0.6% 4.2% 29.5% M3 J1 to J2 335937_2 3,270 3,278 3,319 3,520 8 49 250 0.2% 1.5% 7.6% mainline

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Table 2-12 Traffic Flow Summary in PCU for the M25 for the PM Peak Hour (1700 – 1800)

Flow Difference from SA % Change from SA Link ID Road SA SB SC SD SB SC SD SB SC SD M25 Anticlockwise 77477_2 J14 on slip 1,352 1,356 1,357 1,356 4 5 4 0.3% 0.4% 0.3% M25 J14 to J13 70572_1 8,305 8,326 8,340 8,354 21 35 49 0.3% 0.4% 0.6% mainline 77427_2 M25 J13 off slip 994 1,011 1,022 1,024 17 28 30 1.7% 2.8% 3.0% 121339_1 M25 J13 on slip 1,065 1,058 1,066 1,070 -7 1 5 -0.7% 0.1% 0.5% M25 J13 to J12 335270_2 8,375 8,373 8,383 8,400 -2 8 25 0.0% 0.1% 0.3% mainline M25 Clockwise M25 J12 to J13 77347_2 7,744 7,753 7,768 7,767 9 24 23 0.1% 0.3% 0.3% mainline 121338_1 M25 J13 off slip 719 719 721 719 0 2 0 0.0% 0.3% 0.0% 90692_1 M25 J13 on slip 1,292 1,283 1,295 1,288 -9 3 -4 -0.7% 0.2% -0.3% M25 J13 to J14 70573_2 8,317 8,317 8,343 8,336 0 26 19 0.0% 0.3% 0.2% mainline 269598_2 M25 J14 off slip 426 429 448 443 3 22 17 0.7% 5.2% 4.0% 323637_2 M25 J14 on slip 1,995 1,980 1,988 1,999 -15 -7 4 -0.8% -0.4% 0.2% A30 Eastbound M25 J14 to 70565_2 Crooked Billet 1,193 1,208 1,239 1,222 15 46 29 1.3% 3.9% 2.4% roundabout Crooked Billet Roundabout to 319358_2 871 882 891 883 11 20 12 1.3% 2.3% 1.4% Bulldog Junction Bulldog Junction 77458_1 towards 552 557 568 560 5 16 8 0.9% 2.9% 1.4% Clockhouse Rounabout A30 Westbound Clockhouse Roundabout to 402940_1 981 994 1,007 999 13 26 18 1.3% 2.7% 1.8% Bulldog Junction

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Flow Difference from SA % Change from SA Link ID Road SA SB SC SD SB SC SD SB SC SD Bulldog Junction to 77411_2 1,032 1,042 1,044 1,047 10 12 15 1.0% 1.2% 1.5% Crooked Billet Roundabout Crooked Billet 70564_1 Roundabout to 1,344 1,340 1,367 1,355 -4 23 11 -0.3% 1.7% 0.8% M25 J14 M3 Eastbound M3 J2 to J1 335933_1 2,458 2,463 2,478 2,559 5 20 101 0.2% 0.8% 4.1% mainline 77854_1 M3 J1 off slip 572 574 582 644 2 10 72 0.3% 1.7% 12.6% 77888_1 M3 J1 on slip 693 637 649 1,085 -56 -44 392 -8.1% -6.3% 56.6% M3 J1 to A316 91959_1 2,849 2,826 2,845 3,000 -23 -4 151 -0.8% -0.1% 5.3% mainline M3 Westbound A316 to M3 J1 254742 3,077 3,092 3,136 3,391 15 59 314 0.5% 1.9% 10.2% mainline 77889_2 M3 J1 off slip 678 689 718 726 11 40 48 1.6% 5.9% 7.1% 77857_2 M3 J1 on slip 654 646 651 652 -8 -3 -2 -1.2% -0.5% -0.3% M3 J1 to J2 335937_2 2,840 2,831 2,838 2,934 -9 -2 94 -0.3% -0.1% 3.3% mainline

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The delay at merges has been calculated in the model using the formula specified in WebTAG2. The result of which is added to the calculated link generalised cost used in assignment3.

Table 2-13 presents the calculated merge delay for all merge nodes for the weekday AM and PM peak hours. The additional merge delay only applies if the RFC of the downstream mainline is greater than 0.75, otherwise a value of 0 is presented.

As shown in Table 2-13 the greatest merge delay is at both the M25 J13 clockwise on slip and the M25 J14 anticlockwise on slip, during the AM peak hour in each scenario.

In the PM peak hour, the greatest merge delay is 30 seconds per vehicle, found on the M25 Junction 13 anticlockwise slip in Scenarios C and D.

The largest increases in additional delay per vehicle occur in Scenario D. Most notably there is a 3 second additional delay per vehicle increase on the M3 Junction 1 eastbound on slip to the A316.

Table 2-13 Merge Delay (seconds per vehicle) for the AM and PM Peak Hour

Merge Delay (s/veh) Difference from SA SA SB SC SD SB SC SD AM Peak Hour (0800-0900) M3 J1 westbound on slip 0 0 0 0 - - - M25 J13 clockwise on slip 30.6 30.6 31.2 31.8 0.00 0.60 1.20 M3 J1 eastbound on slip to the 6 6.6 7.2 9 0.60 1.20 3.00 A316 M25 J14 exit merging with M25 0 0 0 0 - - - anticlockwise on slip M25 J13 anticlockwise on slip 28.8 29.4 29.4 28.8 0.60 0.60 0.00 M25 J14 anticlockwise on slip 30.6 31.2 31.2 31.2 0.60 0.60 0.60 PM Peak Hour (1700-1800) M3 J1 westbound on slip 0 0 0 0 - - - M25 J13 clockwise on slip 28.2 28.2 28.8 28.8 0 0.6 0.6 Sunbury Cross roundabout exit 0 0 0 0 - - - merging with the A316 eastbound M25 J14 exit merging with M25 0 0 0 0 - - - anticlockwise on slip M25 J13 anticlockwise on slip 29.4 29.4 30 30 0 0.6 0.6 M25 J14 anticlockwise on slip 28.2 28.2 28.8 29.4 0 0.6 1.2

2.8 Cross Boundary Impacts

Traffic flows on A principal and B roads which cross into neighbouring authorities have been analysed and compared. Table 2-14 presents the flows entering and Table 2-15 presents the flows exiting the Borough for the weekday AM peak hour; Table 2-16 and Table 2-17 also present the traffic flows entering and exiting the Borough but for the PM peak hour. The roads have been listed in a clockwise direction, starting with the London Borough of Hillingdon.

It can be seen that, for the most part, any change in flow in comparison with Scenario A at the Borough’s boundary is relatively small during both time periods with the majority of changes in flow less than 50 PCU. There are some routes which prove to be an exception to this observation. The A308 Portland Bridge cross boundary with the London Borough of Richmond upon

2 WebTAG unit M3.1 (DfT, 2014) Highway Assignment Modelling: Appendix D.9 Merge Modelling on High Speed Roads 3 More detail regarding this method is provided in TN5: SINTRAM Model Technical Report

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Thames has increases of above 150 PCU both exiting the Borough (both time periods) and entering the Borough (PM only) in Scenario D. The maximum percentage increase for this route is reported for PCUs entering the Borough during the PM assessed period (29.9%). The largest change in flow associated with the Runnymede Borough boundary is on the M3. AM trips egressing Spelthorne Borough increase by 250 PCU (7.6%) during the AM peak hour of Scenario D. This is a motorway managed by Highways England and further analysis on such roads can be found in Section 2.7. The largest increase to occur at the boundary with the London Borough of Hounslow is 314 PCUs (10.2%) entering Spelthorne during the PM assessed hour on the A316 Country Way. Again, this increase is associate with the proposed development of Kempton Park, Scenario D. This route is managed by TfL within London and Highways England outside, as such, further analysis can be found in Section 2.7. The increased PCUs associated with Scenario D are also illustrated by the select link flow plots of the Kempton Park development in Section 2.3. When comparing the LoS in Scenarios B to D with the Do Minimum Scenario A, the changes of flow have not led to a change in LoS for any of the cross-boundary A and B roads. The following cross-boundary routes have a high level of service (C or D) but this is maintained in every scenario: - M25 Mainline northbound and southbound, LoS C and D; - A316 westbound approach to Sunbury Cross roundabout, LoS C; and - A244 Walton Bridge Road (both exiting and entering), LoS D.

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Table 2-14 AM Peak Hour Traffic Flow Summary for A Principal and B Roads which enter the Spelthorne Boundary from Neighbouring Authorities

Crosses Link ID Road Flow PCU Difference from SA % change Boundary with SA SB SC SD SB SC SD SB SC SD London Borough 319352_1 A3044 Stanwell Moor Road 758 727 745 739 of Hillingdon -31 -13 -19 -4.1% -1.7% -2.5% London Borough 255240_2 A30 London Road 894 888 881 881 of Hounslow -6 -13 -13 -0.7% -1.5% -1.5% London Borough 77423_2 B3003 Clockhouse Lane 449 441 452 456 of Hounslow -8 3 7 -1.8% 0.7% 1.6% London Borough 91926_2 B377 Feltham Road 152 149 151 150 of Hounslow -3 -1 -2 -2.0% -0.7% -1.3% London Borough 91908_2 A244 Chertsey Road 607 601 597 633 of Hounslow -6 -10 26 -1.0% -1.6% 4.3% London Borough 373 254742_2 A316 Country Way 3753 3717 3781 of Hounslow 8 -36 -15 28 -1.0% -0.4% 0.7% London Borough 324575_2 A308 Portland Bridge of Richmond 942 935 930 927 upon Thames -7 -12 -15 -0.7% -1.3% -1.6% Elmbridge 132 91372_2 A244 Walton Bridge Road 1332 1328 1361 Borough 8 -4 -4 29 -0.3% -0.3% 2.2% Runnymede 90292_2 B375 Bridge Road 374 371 370 373 Borough -3 -4 -1 -0.8% -1.1% -0.3% Runnymede 306 335933_1 M3 3070 3059 3074 Borough 1 -11 -9 4 -0.4% -0.3% 0.1% Runnymede 90549_1 A308 Staines Bridge 530 519 522 517 Borough -11 -8 -13 -2.1% -1.5% -2.5% Windsor and 90566_1 B376 Wraysbury Road 724 683 686 683 Maidenhead -41 -38 -41 -5.7% -5.2% -5.7% Windsor and 121865_2 B376 Heron Lake Road 734 741 743 738 Maidenhead 7 9 4 1.0% 1.2% 0.5% Windsor and 843 70573_2 M25 Clockwise 8406 8412 8460 Maidenhead 9 6 33 54 0.1% 0.4% 0.6% London Borough 764 338495_2 M25 Anti-clockwise 7648 7648 7648 of Hillingdon 7 0 -1 0 0.0% 0.0% 0.0% Junction 14 southbound off London Borough 269599_1 546 558 575 573 slip onto the M25 of Hillingdon 12 29 27 2.2% 5.3% 4.9% Southwest road from Western London Borough 323616_2 Perimeter Road joining the 230 229 229 228 of Hillingdon M25 southbound. -1 -1 -2 -0.4% -0.4% -0.9%

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Crosses Link ID Road Flow PCU Difference from SA % change Boundary with SA SB SC SD SB SC SD SB SC SD Windsor and 178 - - 335342_1 A30 NB approach to M25 J13 1785 1780 1768 Maidenhead 3 -5 -2 -17 -0.3% 0.1% 1.0%

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Table 2-15 AM Peak Hour Traffic Flow Summary for A Principal and B Roads which exit the Spelthorne Boundary into Neighbouring Authorities

Difference from Crosses Link ID Road Flow PCU SA % change Boundary with S SA SB SC SD B SC SD SB SC SD London Borough 72486_1 A3044 Stanwell Moor Road 1272 1299 1311 1310 27 39 38 2.1% 3.1% 3.0% of Hillingdon London Borough 242762_1 A30 London Road 803 821 840 845 18 37 42 2.2% 4.6% 5.2% of Hounslow London Borough 77423_1 B3003 Clockhouse Lane 912 914 927 923 2 15 11 0.2% 1.6% 1.2% of Hounslow London Borough 91926_1 B377 Feltham Road 124 126 129 126 2 5 2 1.6% 4.0% 1.6% of Hounslow London Borough 170853_1 A244 Chertsey Road 938 941 977 961 3 39 23 0.3% 4.2% 2.5% of Hounslow London Borough 91959_1 A316 Country Way 3364 3373 3390 3417 9 26 53 0.3% 0.8% 1.6% of Hounslow London Borough 324575_1 A308 Portland Bridge of Richmond upon 726 730 747 909 4 21 183 0.6% 2.9% 25.2% Thames Elmbridge 91372_1 A244 Walton Bridge Road 1322 1329 1345 1355 7 23 33 0.5% 1.7% 2.5% Borough Runnymede 90292_1 B375 Bridge Road 679 684 727 725 5 48 46 0.7% 7.1% 6.8% Borough Runnymede 72456_1 M3 3270 3278 3319 3520 8 49 250 0.2% 1.5% 7.6% Borough Runnymede 90549_2 A308 Staines Bridge 990 1011 1043 1031 21 53 41 2.1% 5.4% 4.1% Borough Windsor and 90566_2 B376 Wraysbury Road 355 368 369 363 13 14 8 3.7% 3.9% 2.3% Maidenhead Windsor and - 121864_1 B376 Heron Lake Road 718 685 685 689 -33 -29 -4.6% -4.6% -4.0% Maidenhead 33 Windsor and 90441_2 M25 Anti-Clockwise 7021 7023 7041 7042 2 20 21 0.0% 0.3% 0.3% Maidenhead London Borough 338492_1 M25 Clockwise 7002 7007 7026 7059 5 24 57 0.1% 0.3% 0.8% of Hillingdon

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Difference from Crosses Link ID Road Flow PCU SA % change Boundary with S SA SB SC SD B SC SD SB SC SD London Borough 269598_2 M25 NB off-slip Junction 14 783 782 786 779 -1 3 -4 -0.1% 0.4% -0.5% of Hillingdon M25 off-slip northeast London Borough 323595_1 approach to Western 621 624 627 622 3 6 1 0.5% 1.0% 0.2% of Hillingdon Perimeter Road A30 and J13 southbound Windsor and 335359_2 2729 2773 2765 2725 44 36 -4 1.6% 1.3% -0.1% exit from Junction 13 Maidenhead

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Table 2-16 PM Peak Hour Traffic Flow Summary for A Principal and B Roads which enter the Spelthorne Boundary from Neighbouring Authorities

Crosses Boundary Difference from Link ID Road with Flow PCU SA % change SA SB SC SD SB SC SD SB SC SD A3044 Stanwell Moor London Borough of 319352_1 972 1007 1032 1007 35 60 35 3.6% 6.2% 3.6% Road Hillingdon London Borough of 255240_2 A30 London Road 775 788 796 794 13 21 19 1.7% 2.7% 2.5% Hounslow B3003 Clockhouse London Borough of 77423_2 499 500 519 504 1 20 5 0.2% 4.0% 1.0% Lane Hounslow London Borough of 91926_2 B377 Feltham Road 167 164 171 186 -3 4 19 -1.8% 2.4% 11.4% Hounslow London Borough of 91908_2 A244 Chertsey Road 592 596 605 623 4 13 31 0.7% 2.2% 5.2% Hounslow London Borough of 254742_2 A316 Country Way 3077 3092 3136 3391 15 59 314 0.5% 1.9% 10.2% Hounslow London Borough of 324575_2 A308 Portland Bridge Richmond upon 737 744 751 957 7 14 220 0.9% 1.9% 29.9% Thames A244 Walton Bridge 91372_2 Elmbridge Borough 1295 1300 1326 1386 5 31 91 0.4% 2.4% 7.0% Road 90292_2 B375 Bridge Road Runnymede Borough 713 727 755 830 14 42 117 2.0% 5.9% 16.4%

335933_1 M3 Runnymede Borough 2458 2463 2478 2559 5 20 101 0.2% 0.8% 4.1% 90549_1 A308 Staines Bridge Runnymede Borough 1036 1058 1083 1067 22 47 31 2.1% 4.5% 3.0% Windsor and 90566_1 B376 Wraysbury Road 365 378 390 385 13 25 20 3.6% 6.8% 5.5% Maidenhead Windsor and 121865_2 B376 Heron Lake Road 804 790 794 792 -14 -10 -12 -1.7% -1.2% -1.5% Maidenhead Windsor and 77347_1 M25 Clockwise 7,744 7,753 7,768 7,767 9 24 23 0.1% 0.3% 0.3% Maidenhead London Borough of 338495_2 M25 Anti-clockwise 6,953 6,970 6,982 6,999 17 29 46 0.2% 0.4% 0.7% Hillingdon Junction 14 London Borough of 269599_1 southbound offslip onto 947 949 951 949 2 4 2 0.2% 0.4% 0.2% Hillingdon the M25 Southwest road from Western Perimeter London Borough of 323616_2 405 407 406 407 2 1 2 0.5% 0.2% 0.5% Road joining the M25 Hillingdon southbound.

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Crosses Boundary Difference from Link ID Road with Flow PCU SA % change SA SB SC SD SB SC SD SB SC SD A30 NB approach to Windsor and 335342_1 2,084 2,101 2,132 2,111 17 48 27 0.8% 2.3% 1.3% M25 J13 Maidenhead

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Table 2-17 PM Peak Hour Traffic Flow Summary for A Principal and B Roads which exit the Spelthorne Boundary into Neighbouring Authorities

Difference from Link ID Road Crosses Boundary with Flow PCU SA % change SA SB SC SD SB SC SD SB SC SD A3044 Stanwell Moor London Borough of 72486_1 823 821 826 818 -2 3 -5 -0.2% 0.4% -0.6% Road Hillingdon London Borough of 242762_1 A30 London Road 526 528 533 530 2 7 4 0.4% 1.3% 0.8% Hounslow B3003 Clockhouse London Borough of 77423_1 474 458 470 461 -16 -4 -13 -3.4% -0.8% -2.7% Lane Hounslow London Borough of - 91926_1 B377 Feltham Road 106 105 100 95 -1 -6 -11 -0.9% -5.7% Hounslow 10.4% London Borough of 170853_1 A244 Chertsey Road 638 631 647 677 -7 9 39 -1.1% 1.4% 6.1% Hounslow London Borough of 91959_1 A316 Country Way 2849 2826 2845 3000 -23 -4 151 -0.8% -0.1% 5.3% Hounslow London Borough of 324575_1 A308 Portland Bridge 768 762 761 939 -6 -7 171 -0.8% -0.9% 22.3% Richmond upon Thames A244 Walton Bridge 91372_1 Elmbridge Borough 1204 1200 1203 1235 -4 -1 31 -0.3% -0.1% 2.6% Road 90292_1 B375 Bridge Road Runnymede Borough 321 318 318 311 -3 -3 -10 -0.9% -0.9% -3.1%

72456_1 M3 Runnymede Borough 2840 2831 2838 2934 -9 -2 94 -0.3% -0.1% 3.3% 90549_2 A308 Staines Bridge Runnymede Borough 587 575 589 587 -12 2 0 -2.0% 0.3% 0.0% B376 Wraysbury 90566_2 Windsor and Maidenhead 750 735 742 733 -15 -8 -17 -2.0% -1.1% -2.3% Road B376 Heron Lake 121864_1 Windsor and Maidenhead 578 586 597 593 8 19 15 1.4% 3.3% 2.6% Road 90441_2 M25 Anti-Clockwise Windsor and Maidenhead 7310 7315 7318 7330 5 8 20 0.1% 0.1% 0.3% London Borough of 338492_1 M25 Clockwise 7701 7698 7704 7703 -3 3 2 0.0% 0.0% 0.0% Hillingdon M25 NB off-slip London Borough of 269598_2 426 429 448 443 3 22 17 0.7% 5.2% 4.0% Junction 14 Hillingdon M25 off-slip northeast London Borough of 323595_1 approach to Western 190 190 191 190 0 1 0 0.0% 0.5% 0.0% Hillingdon Perimeter Road

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Difference from Link ID Road Crosses Boundary with Flow PCU SA % change SA SB SC SD SB SC SD SB SC SD A30 and J13 335359_2 southbound exit from Windsor and Maidenhead 2,163 2,165 2,184 2,179 2 21 16 0.1% 1.0% 0.7% Junction 13

Given the density of the Highway Network adjoining Spelthorne and the large increases in flow to the east of Kempton Park illustrated in Figure 2-14, additional consideration has been given to impacts further into Hounslow, Kingston and Richmond.

The Apex Corner roundabout comprises several give way junctions with a LoS categorisation of D and comparison between the Do Minimum Scenario A and Scenario D for both peak hours is provided in both Table 2-18 and Table 2-19.

The largest increase in junction delay in Scenario D at the Apex Corner roundabout is 10 seconds during the AM peak hour. This is for the Hampton Road East westbound approach, which has a LoS of D during both the Do Minimum Scenario A and Scenario D. Both the A316 eastbound off slip and the westbound off slip approaches to the Apex Corner Roundabout also have LoS categorisations of D during the Do Minimum Scenario A AM peak hour, which is maintained in the proposed Kempton Park Scenario D.

Table 2-18: Apex Corner AM peak hour Do Minimum Scenario A vs Scenario D proposed Kempton Park development

Delay in seconds per vehicle Performance Do- Node id Name Junction Type SC PM Do- Do- Minimum Difference pk Minimum SC PM Minimum SC AM pk PM RFC pk LOS LoS Hampton Road East westbound approach to Apex Corner 232384 Give Way 43 53 10 1.01 1.03 D D Roundabout 232371 A316 eastbound off slip approach to Apex Corner Roundabout Give Way 53 57 4 1.02 1.03 D D 232379 A316 westbound off slip approach to Apex Corner Roundabout Give Way 14 14 0 1.01 1.02 D D A305 Twickenham Road westbound approach to Apex Corner 232392 Give Way 9 9 0 0.80 0.79 B B Roundabout A312 Hampton Road West eastbound approach to Apex Corner 232383 Give Way 25 25 -1 0.98 0.98 C C Roundabout

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Table 2-19: Apex Corner PM peak hour Do Minimum Scenario A vs Scenario D proposed Kempton Park development

Delay in seconds per vehicle Performance Do- Node id Name Junction Type SC PM Do- Do- Minimum Difference pk Minimum SC PM Minimum SC AM pk PM RFC pk LOS LoS A305 Twickenham Road westbound approach to Apex Corner 232392 Give Way 10 14 4 0.849 0.91 B C Roundabout Hampton Road East westbound approach to Apex Corner 232384 Give Way 9 12 3 0.78 0.88 B C Roundabout 232379 A316 westbound off slip approach to Apex Corner Roundabout Give Way 3 4 1 0.56 0.70 B B 232371 A316 eastbound off slip approach to Apex Corner Roundabout Give Way 8 9 1 0.69 0.74 B B A312 Hampton Road West eastbound approach to Apex Corner 232383 Give Way 8 8 0 0.76 0.78 B B Roundabout

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2.9 Network Hotspots and Mitigation

To summarise the traffic impacts identified in this study, Table 2-20 and Table 2-21 list the junctions and sections of road which experience large vehicle delay, termed ‘hotspots’, which are situated within Spelthorne Borough. They are essentially all links and junctions which have been identified within this report as having a Level of Service (LoS) category of D (forced or breakdown of flow and operating above capacity), or C (unstable fow). Only junctions with an average delay value greater than 1 seconds per vehicle have been included within this category. The hotspots, therefore, include links and junctions which are already categorised in the Do Minimum Scenario A as having a LoS of C or D. This accounts for the majority of the hotspots listed. Those marked with an asterisk are those where the LoS deteriorates to category C or D in one or more of Scenarios B, C and D.

LoS categorisations for links within the Borough of Spelthorne are illustrated in both Figure 2-16 and Figure 2-17.

As presented in Table 2-18 and Table 2-19 there is increased in junction delay at the Apex Corner roundabout, which is on the TfL network. The LoS categorisation for the three arms experiencing the largest increases in junction delay during the AM is D, corresponding to forced, or breakdown of flow, which is maintained throughout all scenarios. This suggests that whilst Scenario D would introduce extra junction delay in the vicinity, there are pre-existing issues at this roundabout which may need to be addressed.

Hotspots are areas of stress where drivers are subject to considerable delay and are likely to require mitigation to facilitate any development in the local area. This could be ‘hard’ or ‘soft’ measure, or most likely a combination of both. Hard engineering measures could involve increasing the number of lanes of the carriageway or introducing a cycle lane, for example, whilst soft measures could be the implementation of a travel plan to encourage travel by sustainable modes.

The hotspots provide a preparatory list of where potential mitigation should be focused, to inform the Borough’s Infrastructure Delivery Plan (IDP) and subsequent Community Infrastructure Levy (CIL).

NOTE: in accordance with the National Planning Policy Framework all individual developments that generate significant amounts of movement should be supported by a specific Transport Statement or Transport Assessment. These are submitted as part of the planning application process.

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Table 2-20 AM peak hour Network Hotspots (*Those marked with an asterisk mean LoS is less than category C in the Do Minimum Scenario A and has subsequently deteriorated).

Area Location LINKS Stanwell Moor M25 Junction 13 - 14 Clockwise Stanwell Moor M25 Junction 14 – 13 Anticlockwise Staines B376 Laleham Road northbound Fordbridge B377 Ashford Road eastbound approach to Fordbridge Roundabout Fordbridge B377 Fordbridge Road westbound approach to Fordbridge Roundabout Staines A30 westbound approach to Crooked Billet Sunbury A308 Staines Road East westbound towards Sunbury Cross Roundabout A244 Walton Bride Road between Walton Lane (roundabout) and A3050 Oatlands Lower Halliford Drive, both directions A244 Walton Bridge Road between Walton Lane and Marshall’s Roundabout Lower Halliford southbound JUNCTIONS Ashford A30 and B378 signalised Bulldog Junction Ashford A308 Staines Road West signalised crossroads with B378 School Road / Ashford Road Ashford A244 Chertsey Road signalised junction with Chertsey Road Ashford B378 School Road / Convent Road signalised crossroads with Feltham Hill Road Ashford B377 Kingston Road eastbound approach to the Fordbridge roundabout Charlton Charlton Lane priority junction with New Road and Charlton Road Fordbridge *Kingston Road signalised junction with Woodthorpe Road Littleton A308 Staines Road signalised crossroads with Littleton Lane and Chertsey Road Lower Halliford A244 Walton Bridge Road roundabout with Walton Lane Lower Halliford A244 Walton Bridge Road priority junction with Walton Lane M25 J13 *A30 Staines bypass signalised approach to the M25 J13 M25 J13 *M25 clockwise off slip signalised approach to Junction 13 M25 J13 *M25 clockwise off slip signalised approach to Junction 13 B376 Laleham Road / Green Road signalised crossroads with High Street / Old Shepperton Charlton Road Shepperton B376 Laleham Road signalised junction with Watersplash Road Staines A308 Staines Bridge Road signalised junction with B376 Hale Street Staines A308 Thames Street signalised junction with B376 Laleham Road Staines A308 South Street signalised junction with Mustard Mill Road Staines B376 Wraysbury Road signalised junction with Hale Street Staines A308 London Road signalised junction with Fairfield Avenue Staines A308 London Road signalised junction with Kingston Road Staines A308 High Street signalised junction with Fairfield Avenue Staines *A308 Thames Street signalised junction with Elmsleigh Road shopping centre Staines *A308 Thames Street signalised junction with Elmsleigh Road shopping centre Stanwell A3044 Stanwell Moor Road signalised junction with B378 Park Road Stanwell Southern Perimeter Road signalised junction with Seaford Road Sunbury A308 Staines Road West signalised crossroads with A244 Windmill Road A244 Windmill Road signalised crossroads with International Way and Brooklands Sunbury Close Sunbury A308 Staines Road West signalised junction with Escort Road Sunbury A308 Staines Road East approach to signalised junction at Sunbury Cross roundabout Sunbury A244 Windmill Road signalised crossroads with Dolphin Road and Windmill Road W Sunbury M3 eastbound off slip signalised approach to the Sunbury Cross roundabout Sunbury Vicarage Road southbound approach to the signalised Sunbury Cross roundabout Sunbury *Green Street northbound approach to signalised Sunbury Cross roundabout Upper Halliford A244 Upper Halliford Bypass signalised junction with Charlton Lane

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Table 2-21 PM peak hour Network Hotspots (*Those marked with an asterisk mean LoS is less than category C in the Do Minimum Scenario A and has subsequently deteriorated).

Area Location LINKS Stanwell Moor M25 Junction 13 - 14 Clockwise Stanwell Moor M25 Junction 14 – 13 Anticlockwise Fordbridge B377 Ashford Road eastbound approach to Fordbridge Roundabout Sunbury A308 Staines Road East westbound towards Sunbury Cross Roundabout A244 Walton Bride Road between Walton Lane (roundabout) and A3050 Oatlands Lower Halliford Drive, both directions A244 Walton Bridge Road between Walton Lane and Marshall’s Roundabout Lower Halliford southbound JUNCTIONS Ashford A308 Staines Road signalised crossroads with Littleton Lane and Chertsey Road Ashford A308 Staines Road West signalised crossroads with B378 School Road / Ashford Road Ashford A30 and B378 signalised Bulldog Junction Ashford B378 School Road / Convent Road signalised crossroads with Feltham Hill Road Fordbridge Kingston Road signalised junction with Woodthorpe Road Lower Halliford A244 Walton Bridge Road roundabout with Walton Lane Lower Halliford A244 Walton Bridge Road priority junction with Walton Lane Lower Halliford *A244 Walton Bridge Road roundabout with Walton Lane M25 J13 M25 clockwise off slip signalised approach to Junction 13 M25 J14 *Horton Road eastbound signalised approach to M25 J14 M25 J14 *Horton Road eastbound signalised approach to M25 J14 Staines B376 Wraysbury Road signalised junction with Hale Street Staines A308 Staines Bridge Road signalised junction with B376 Hale Street Staines A308 Thames Street signalised junction with B376 Laleham Road Staines A308 Thames Street signalised junction with Elmsleigh Road shopping centre Staines A308 South Street signalised junction with Mustard Mill Road Staines A308 London Road signalised junction with Kingston Road Staines *A308 London Road signalised junction with Fairfield Avenue Staines *A308 London Road signalised junction with Fairfield Avenue Stanwell A3044 Stanwell Moor Road signalised junction with B378 Park Road Stanwell Southern Perimeter Road signalised junction with Seaford Road A3044 Stanwell Moor Road northbound approach to roundabout with A3113 Airport Stanwell Way A244 Windmill Road signalised crossroads with International Way and Brooklands Sunbury Close Sunbury A308 Staines Road West signalised crossroads with A244 Windmill Road Sunbury A244 Chertsey Road signalised junction with Chertsey Road Sunbury A244 Windmill Road signalised crossroads with Dolphin Road and Windmill Road W Sunbury Green Street northbound approach to signalised Sunbury Cross roundabout Sunbury Vicarage Road southbound approach to the signalised Sunbury Cross roundabout Sunbury *A308 Staines Road West signalised junction with Escort Road Sunbury *A308 Staines Road East approach to signalised junction at Sunbury Cross roundabout Sunbury *A308 Staines Road West signalised junction with Escort Road Sunbury *A308 Staines Road East approach to signalised junction at Sunbury Cross roundabout Sunbury *A308 Staines Road West signalised junction with Escort Road Upper Halliford A244 Upper Halliford Bypass signalised junction with Charlton Lane

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3 OVERVIEW OF FINDINGS

The potential highway impacts of Spelthorne Borough Council’s draft Regulation 18 Local Plan have been assessed for the forecast year 2035 using a combination of Surrey County Council’s strategic transport model, SINTRAM, and a local model derived from it.

Four model scenarios have been created: - Scenario A: Do Minimum. This scenario includes all background growth as well as committed developments identified from the base year (since 2014) to the forecast year 2035, where committed developments comprise sites already built, or in the process of construction, or have planning permission.

- Scenario B: Growth Option 1. As Scenario A plus sites most likely to be developed by the future year (including potential urban site allocations and SLAA sites).

- Scenario C: Growth Option 2. As Scenario B, also includes potential green belt site allocations.

- Scenario D: Kempton Park Bespoke Scenario. As Scenario B, also includes the proposed development at Kempton Park, instead of the greenbelt site allocation identified in Scenario C.

The potential highway impacts of the draft Regulation 18 Local Plan have therefore been identified by comparing the Do Minimum Scenario A with each of the Growth Option Scenarios B to D.

Links and junctions within the Borough which have been forecasted to be under stress, where drivers will be subject to considerable delay, have been defined as ‘hotspots’. These hotspots, set out in Section 2.9, are likely to require mitigation to reduce the impact of any development in the local area, and provide a preparatory list to inform the Borough’s Infrastructure Delivery Plan (IDP) and subsequent Community Infrastructure Levy (CIL). It should be noted that the majority of these locations already experience congestion issues which are exacerbated by the additional trips arising from the potential development sites or as a result of re- routing caused by additional traffic generated by development.

3.2 Key Points

The primary impacts of Spelthorne Borough Council’s draft Regulation 18 Local Plan on the highway network can be summarised as follows: 1) The overview of the Local Plan scenarios provided by the Borough’s network statistics reported in Section 2.2 show that: a. The total vehicle trips are lowest in the Do Minimum Scenario A and greatest in Scenario D, which contains all most likely development sites and the potential Kempton Park development. Scenarios B and C also model increases in vehicle trips, but both fewer than Scenario D. b. With total distance and travel time being greater during the AM peak hour, it is more congested than the PM peak hour, as peak commuting and education escort trips coincide. c. All Local Plan Growth Option Scenarios have greater impacts when compared with the Do Minimum Scenario A.

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d. Scenario D has the largest increase in total vehicle distance travelled. Scenario D contains the greatest number of vehicular trips and in turn the greatest highway impact in both the AM and the PM peak hour. 2) Highway select link analysis has been undertaken to show the routing of vehicles accessing and egressing the largest of the assessed potential development sites in Scenarios C and D for the single AM and PM peak hours. The development sites that select link analysis was performed for account for much of the differences between Scenarios C/D and A due to their size. The analysis showed vehicles predominantly routing and dispersing via the main roads close to the development sites. 3) The largest increases in flow in all scenarios, when compared to the Do Minimum Scenario A, are mostly on the main corridors of M3, M25, A30, A320 and A308. Minor decreases in traffic flow are also evident in the highway network in all scenarios. Small reductions in flow are occurring on a sample of roads in the south of the Borough in the AM Staines area and the A3044 Stanwell Moor Road, when compared to the Do Minimum Scenario A. This is an impact of re-routing generated by small changes in local congestion, and highlighting the sensitivity of changes in vehicle trips to the surrounding area. 4) Flow difference plots show that Scenario B seems to impact more on Staines, and so when developers take forward their proposals here (should they be allocated within the draft Local Plan) then a cumulative approach may need to be taken as opposed to looking at their developments in isolation. The Borough, together with their colleagues in Transport Development Planning, may wish to think about how this can be done. It is possible that the development of a microsimulation model of Staines would be a useful step. 5) Routes such the A308, A244, B376 and the B378, and areas such as Sunbury, Laleham and Charlton appear to be impacted mostly in Scenario C. 6) The junctions with particularly large delay values are present in all scenarios, and have also been shown to be operating near or over capacity in all scenarios. This is regardless of the addition of any Local Plan strategic sites. As a result, existing congestion would be exacerbated in these locations, causing a reduction in driver comfort levels and increased stress due to further deterioration of traffic conditions. 7) Junctions which are impacted in each scenario are not necessarily those in the immediate vicinity of the larger sites. The combination of the potential development sites together with committed development means that for any junction which is close to capacity, a small amount of additional traffic may tip the balance resulting in a deterioration in performance. This additional traffic may relate to development or be comprised of existing traffic re-routing as a result of traffic generated by development. 8) Link flow and merge delay analysis of the Strategic Highway Network indicated large variations between scenarios D and A. Scenario D has by far the greatest increase in flow on the Strategic Highway Network, with a maximum 250 additional PCUs on the M3 westbound during the AM peak hour. 9) Cross boundary roads with neighbouring local authorities experience both increases and decreases in traffic flow entering and exiting the Borough in all assessed Local Plan scenarios. However, the changes in flow does not cause the LoS values to worsen for any of the cross boundary A and B

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roads, when compared to the Do Minimum Scenario A. The following cross- boundary routes have a high level of service (C or D) but this is maintained in every scenario: - M25 Mainline northbound and southbound, LoS C and D; - A316 westbound approach to Sunbury Cross roundabout, LoS C; and - A244 Walton Bridge Road (both exiting and entering), LoS D.

Given the extent of Highways England’s network within the borough appropriate liaison will be essential and there is likely to be the need for additional analysis work in relation to a regulation 19. Furthermore, there is likely to be a need for a more extensive analysis of cross boundary impacts even if Scenario D is not taken forward. Sufficient time would be required to allow this work to be done.

Further analysis relating to development sites and their potential mitigation efforts should be focused on areas where the highway network is performing under existing pressure. This report highlights that few new hotspots emerge but instead existing highway conditions are exacerbated by development trips and/or existing trips re- routing as a result of greater traffic volumes.

This is an initial assessment, and more work will need to be done when the Borough have decided on their preferred spatial strategy. Once complete, and prior to assessment commencing, this report can be used as a starting point to consider mitigation. Highways England will be interested in how vehicular trips from new developments can be further reduced as part of the planning and mitigation process, prior to working on junction mitigation.

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