Land at Potterells Farm, Welham Green Welwyn and Hatfield Local Plan – Site Allocations in Welham Green
14th July 2017 N03-IS-151913-Site Allocations Update-01
Introduction
1. This Technical Note considers potential effects and sets out the transport benefits of the cumulative development of 450 dwellings in Welham Green within Sites WeG1, WeG3, WeG6, WeG10, WeG12 and WeG15 (‘the southern development sites’), setting out the transport benefits which can be delivered from a strategic approach to development.
2. The cumulative delivery of circa 450 dwellings in Welham Green within the southern development sites would support the aims and objectives of Hertfordshire County Council’s (HCC) Local Transport Plan 3 (LTP3). Two key elements of LTP3 are increased use of ‘intelligent transport systems’ (which includes optimising traffic signals and providing real time information) and promotion of sustainable travel to reduce growth in car traffic. The way in which the cumulative delivery of housing in Welham Green within the southern development sites promotes sustainable travel is explained in this Technical Note.
3. The importance of delivering sustainable development cannot be understated. The County Council's aim to achieve a modal shift would not only bring about environmental improvements, it would also deliver more socially inclusive communities, and a mode shift away from the car to more sustainable forms of transport would also free up capacity in the highway network and thus help deliver sustainable growth. Therefore, providing for sustainable travel should be a critical focus of new development and a key way of delivering sustainable growth.
4. The traffic modelling work which has been undertaken to date in relation to Welham Green is considered robust, and already provides a reasonable forecast of the potential future effect of cumulative development in Welham Green. The Reasons People Travel
Journey Distance / Journey Mode
5. In 2009, 20% of all journeys made in Great Britain covered less than 1 mile (1.6 km), and more than half (56%) of car journeys covered less than 5 miles (8 km) (Department for Transport 2010a, Transport Trends 2009). In 2009/10, 59% of journeys under 1 mile in Hertfordshire were undertaken on foot, and 3% of journeys under 3 miles in Hertfordshire were undertaken by bicycle (HCC LTP3).
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6. The ‘Draft Infrastructure Delivery Plan (Revised January 2015)’ notes that the walking mode share for journeys up to 1 mile is currently 63% in Hertfordshire (2011 Hertfordshire Travel Survey) although walking as a mode of travel to work declined from 10.8% in 2001 to 10.5% in 2011 (Source: Census). In terms of cycling, in countywide terms cycle usage increased 50% between 2004 and 2013 whilst 2013 figures were themselves up 24% on the previous year (HCC Transport and Data report 2014).
7. In terms of journeys to work, approximately 9% of journeys are made by train, and 4.1% of journeys to work are made by either bus, minibus or coach (2011 Census). However, bus usage increased by 5.6% between 2012/13 and 2013/14, reflecting national trends (HCC Transport and Data report 2014). Hertfordshire Traffic and Transport Data Report 2016, September 2016
8. The Hertfordshire Traffic and Transport Data Report (HTTDR) 2016 provides the latest travel data and indicates the way people are choosing to travel is evolving, and travel behaviour is changing, with some trends towards more sustainable mobility.
Traffic Flows
9. Gradually the link between economic growth and traffic growth is breaking. Between 2001 and 2015 population in Hertfordshire has growth by 13%, whilst traffic has grown by 8% during this period. In the last 12 months HGV traffic increased by 3.5%, but the number of HGVs on the network is still 21% down on 2000 levels.
10. Between 2014 and 2015 the number of registered plugged-in vehicles increased by 120%.
Growth Factors
11. Whilst the last 15 years has seen an 8% increase in traffic growth Herts CC is forecasting traffic growth of 13.7% in East Hertfordshire and 13.4% in Welwyn Hatfield between 2015 – 2031, based on National Transport Model (NTM) predictions. The highest level of growth is forecast to be on motorways and trunk roads, with lower levels of growth on the local road network.
12. Whilst the forecast level of traffic growth is not as high as previously predicted, the level of forecast traffic growth in the next 15 years is still nearly double what has been recorded over the previous 15 years.
Travel Behaviour
13. Journeys to work make up a significant proportion of all journeys travelled in Hertfordshire. In 2012 57.6% of people aged 16-74 in Hertfordshire used the car as their main mode of transport to work.
14. Overall, using the car to travel to work is trending downwards whilst rail use has increased.
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Sustainable Travel Patterns
15. The percentage of all journeys under 1 mile in length which were undertaken on foot increased from 58.9% in 2009/10 to 76.5% in 2015.
16. In the 2014 18% of journeys to work in Hertfordshire were less than 3 miles. This increased to 27% in 2015. Over a third of work trips are less than 5 miles.
17. This demonstrates the potential for walking and cycling to undertake a significant proportion of all trips.
Walking
18. Walking is a healthy and sustainable alternative to travelling by car. According to the Active People Travel Survey 2014/2015 88% of people in Hertfordshire walked at least once a month, which is slightly higher than the national level of 86%. Of the walk trips, 38% of walk trips are for social or leisure purposes, with 18% for the purpose of shopping.
Cycling
19. There was a slight increase in cycling as a mode share during the AM peak period (07:00 – 10:00) across all but one town. This is reflected by the fact that 51% of adults owned a useable bicycle, with more men than women owning a bicycle.
Bus
20. In England 83% of bus journeys are less than 10 miles in length. During the 2015/16 financial year there were an estimated 37.9 million bus passenger journeys in Hertfordshire, which is an increase of 9.3% from 2014/15.
Rail
21. Rail travel is an efficient and sustainable method of travel in Hertfordshire. Rail use grew in Hertfordshire by 5% from 2014 to 2015, and rail use in Hertfordshire is significantly higher (13%) than the national average (9%)
22. The 2016 report indicates that 76% of trips by rail were for the purpose of travelling to work.
Car Share
23. There has been an increase in the number of registrations to Herts CC car share initiative, Hertsliftshare.org. Registrations in 2015 increased to 464, which is a 16% increase from the previous year. A total of 4% of all travel to work trips were accounted for through car sharing / passengers, indicating this is a growing mode share with significant potential for further growth.
School Travel
24. In terms of school travel levels of car use and walking have remained relatively stable since 1999, whilst cycling has increased and bus use has dropped.
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25. The mode share of sustainable school journeys (5 – 10 year olds) has increased from 58% in 2014/15 to 69% in 2015/16. The increase in the mode of sustainable school journeys (11 – 16 year olds) is from 74% in 2014/15 to 79% in 2015/16.
26. The potential of providing high-quality, attractive infrastructure to support walking, cycling and public transport is significant, and can make a real difference in influencing people’s travel behaviour and supporting the objectives of the Council in terms of sustainable travel. Journey Purpose
27. The National Travel Survey, which consists of a face-to-face interview and a seven day self- completed written travel diary, allows us to understand trips by journey purpose, and the mode split of trips for each purpose.
28. Trips can be classified into three general journey purposes, commuting, education, leisure / recreation, with the proportion of trips for each purpose as summarised in Table 1.
Table 1 – Trips by Journey Purpose – Commuting, Education, Leisure / Recreation Start Time Commuting Education Leisure / Recreation AM (08:00-08:59) 26% 50% 24% PM (17:00-17:59) 38% 4% 58%
29. The NTS data demonstrates that in the AM peak 50% of journeys are undertaken for the purpose of education, reducing to 4% in the PM peak. Of these journeys, approximately 50% relate to primary education, and 50% to secondary education.
30. We understand that the existing primary school in Welham Green (Saint Mart’s CoE Primary School) is close to or at capacity. We understand the delivery of development in Welham Green could facilitate the provision of a new primary school in Welham Green, which will be able to cater for surplus existing demand and new demand in a sustainable manner, allowing students to travel to and from the school on foot or by bicycle.
31. In terms of new development, this would cater for approximately 25% of all trips in the morning peak period, as well as removing existing local car-based primary education trips from the network, and align and support the target in Hertfordshire County Council’s LTP 3 to increase the mode share of sustainable primary school journeys from 61.7% to 73% by 2031. Sustainable Development
32. There are a number of inherent advantages of delivering circa 450 dwellings in Welham Green within the southern development sites. These include:
• A plethora of local facilities, including shops, health facilities, a primary school and leisure and recreation facilities;
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• A number of employment opportunities – a total of 3,015 people work in Welham Green, and 221 of the 2,408 residents live and work in Welham Green – approximately 9%; • The existing network of walking and cycling routes, including National Cycle Route 12; and • The proximity of public transport services, including Welham Green rail station and a number of local bus stops.
33. The cumulative development of circa 450 dwellings within the southern development sites could further enhance and support the opportunities and infrastructure in Welham Green, providing critical mass to potentially support walking and cycling route enhancements, improved bus services, and sustainable infrastructure, with direct, attractive links, providing a network of connections between new development and the existing urban area.
34. Transport policy, and planning policy, is aiming to break the link between economic growth and traffic growth, delivering growth in a sustainable manner. The potential for economic growth should not be constrained or limited by the highway network.
35. Whilst the highway network may be busy at peak periods, this should not mean new development is prohibited. Indeed, new development can help facilitate a mode shift towards sustainable transport modes, and provide greater opportunities for travel for new and existing residents.
36. Transport policy no longer aims to ‘predict and provide’ in terms of highway capacity, and whilst new development can deliver highway improvements – including intelligent highway systems – junction capacity does not define the acceptability of development. The ability to deliver sustainable development is a more important consideration. Welham Green Transport Strategy
37. The opportunity exists to develop a Welham Green Transport Strategy which each separate proposed development supports, providing a joined up approach to transport.
38. Whilst individual sites can contribute towards delivering the Council’s sustainable travel objectives, this can often be at a local scale. The advantage of the cumulative delivery of the southern development sites at Welham Green is the opportunity to deliver tangible transport improvements which will benefit both existing and future residents, improving opportunities for walking, cycling and public transport for local journeys, and make a noticeable difference to the way people choose to travel.
39. A joined-up approach can be more successful at delivering a mode shift towards sustainable travel, and the cumulative impact of circa 450 dwellings, delivered to support the same strategy, would be less than what would be considered reasonable (and previously assessed) when reviewing each site individually. There is a greater potential for linked trips between new developments, particularly with the delivery of a primary school, and therefore the overall cumulative effect of circa 450 dwellings would be less than taking the individual impact of each site in turn and inputting this into a model.
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Modelling Work
40. We have looked into the modelling work undertaken to date in relation to Welham Green. The 18th March 2015 transport comments from HCC explain that although the villages to the south of the borough (including Welham Green) are outside the WHaSH modelling area, traffic travelling north from the suggested development allocations has been included. The way that the possible development allocations have been coded into the model is clearly robust and as HCC explain, “the modelling work is likely to have overestimated the levels of traffic from development in the Hatfield area”.
41. This overestimation is effectively confirmed by HCC in their statement that as the larger number of sites in Brookmans Park and Welham Green included in the modelling work “are outside the model area the impact of this discrepancy [the overestimate] on the highway locations coming under pressure and the proposed mitigation measures are likely to be minimal”.
42. In addition to this, the potential for the comprehensive planning and integration of the Welham Green southern development sites would result in a degree of internalisation and containment of trips locally, and facilitate access to local facilities, including a potential new primary school, reducing net external traffic generation on Dixons Hill Road and the A1000.
43. Therefore, the assessment work which has been undertaken to date is considered robust, and Welham Green has the capacity to accommodate future development without any adverse transport impacts. WHaSH (Welwyn Hatfield and Stevenage-Hitchin) Highway Model Welwyn Hatfield Local Plan Mitigation Testing, August 2016
44. The latest modelling work in relation to the Local Plan is set out in the WHaSH.
45. The WHaSH Report tests different development scenarios for the Local Plan and develops a number of highway mitigation scheme proposals in Welwyn and Hatfield to help mitigate the impacts of new developments on the road network.
46. WHaSH is a strategic model and as such, is not suitable for detailed junction simulation or detailed scheme design, but can be used as a tool to provide an indication of potential hotspots on the network and the potential impact of high level mitigation strategies.
47. When the latest report (August 2016) was compiled, the Local Plan horizon year was changed to 2032, 2031. WHaSH forecast scenarios were originally developed for year 2031. Despite the changes, the forecast year has been kept unchanged for consistency with other undertaken modelling work for WHBC. It was concluded that this is a good approximation to the end of the Plan period, and this is a reasonable approach and position to take.
48. Two alternative Local Plan development scenarios have been considered in the August 2016 report. Scenario 1 is expected to more closely represent the final Local Plan proposals but it was decided to also test Scenario 2 when developing the mitigation schemes because as this
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has a higher level of forecasted development. Scenario 2 represents the “worst-case” scenario for the highway network given the additional demand for transport created.
49. The proposed development sites in the vicinity of Welham Green included in each scenario are shown in Figure 1.
Figure 1 – Development Sites Included In Scenario 1 and Scenario 2
50. WeG1, WeG3, WeG6, WeG10, WeG12 and WeG15 (‘the southern development sites’) are not included in either scenario.
51. A total of 16 mitigation schemes were previously assessed in the model. The original mitigation proposals, which are detailed in full in Welwyn and Hatfield Junction Design Improvement Feasibility Study, form the basis of improvements developed in the August 2016 report.
52. However, in the August 2016 report three additional mitigation schemes were assessed, as summarised in Figure 2:
Figure 2 – Additional Mitigation Schemes Assessed in 2016 Report
53. None of the three additional mitigation schemes summarised in Figure 2 are of particular relevance to the development sites.
54. The two mitigation schemes which are closest to the development sites are Mitigation Scheme 7 and Mitigation Scheme 16. Mitigation Scheme 16 is of most relevance to the development sites.
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Figure 3 – Location of Mitigation Schemes
55. The development of these mitigation schemes was undertaken with a view to be achievable in the short term. Primarily, the mitigation proposals are focused on changes to the road layout or signals in order to improve efficiency of the existing road network.
Mitigation Scheme 7 – A1 (M) Junction 3
56. The location of Mitigation Scheme 7 is shown in more detail in Figure 4.
Figure 4 – Mitigation Scheme 7 – A1 (M) Junction 3
57. Currently in both periods, sections of the roundabout have a Volume to Capacity ratio of more than 90%, in the AM period the A1(M) NB off-slip is at capacity as is Roehyde Way NB in the PM period.
58. In the AM period, sections of the roundabout have delays of up to 30 seconds, but there is no significant average delay apart from the A1(M) SB off slip, which has a delay of up to 2.5 minutes for both AM and PM.
59. The original mitigation scheme tested in this location is summarised in Figure 5:
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Figure 5 – Mitigation Scheme 7 – Original Mitigation Proposals
60. The final mitigation proposals tested in the 2016 report are summarised in Figure 6:
Figure 6 – Mitigation Scheme 7 – Revised Mitigation Scheme
61. 62. Overall, issues on the highway network are affected by the introduction of all of the schemes together rather than independently, as schemes within close proximity are likely to influence each other.
63. In this particular location, the mitigation overall results in reduced delay and improved junction performance. However, in the AM period, congestion relief provided by mitigation in a different location actually leads to congestion increase in this location.
Mitigation Scheme 16 – A1000 and South Way Over-Pass
64. The location of Mitigation Scheme 16 is shown in more detail in Figure 7.
Figure 7 – Mitigation Scheme 16 – A1000 and South Way Over-Pass
65. Whilst this mitigation scheme is closets to the development sites the A1000 and Southway Overpass are located south to Hatfield, close to the boundary of WHaSH. The highway network and demand assumptions are simplified at the model boundaries. The August 2016 report therefore recommends that any interpretation of modelling results should be taken with caution in this location.
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66. Currently, the A1000 has Volume to Capacity ratio in excess 90% in the N/WB direction both the AM and PM time periods and also in the S/EB direction during PM period.
67. In the AM period there are delays indicated at the start of the A1000 N/WB underpass slip road of over 5 minutes. However, this might be as a result of loading the demand from different developments outside the modelled area into the model from a single point, and as the report states this may result in the results not being representative of real life traffic conditions.
68. Notwithstanding this, the assssement of the original mitigation proposals is summarised in Figure 8.
Figure 8 - Assessment of Original Mitigation Proposals
69. The assessment of the revised mitigation proposals is summarised in Figure 9.
Figure 9 - Assessment of Revised Mitigation Proposals
70. The conclusions of the August 2016 report is that the mitigation scheme fully addresses the issues identified, bringing V/C and average junction delay to within acceptable levels for the peak hours. This is less than 90% volume over capacity ratio, or less than 1 minute average delay.
71. Further detail on the model outputs for Mitigation Scheme 7 and Mitigation Scheme 16 are provided at Appendix A. Accessibility Comparison
Current School Site
72. The current school site is situated to the west of Welham Green off Dellsome Lane. The predominant land use in the vicinity of the site is residential.
73. The current site is served by good quality pedestrian routes to and from the east of the school. The 5 minute and 10 minute walking isochrones from the school are shown in Figure 10 and Figure 11 respectively.
74. In the vicinity of the site there are footways on both sides of Dellsome Lane. This lit footway is in good condition and of sufficient width to accommodate pedestrian movement. Dellsome Lane provides a link to Dixons Hill Road and access to local facilities including bus stops.
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Figure 10 – 5 Minute Walking Isochrone From Current School Site
Figure 11 – 10 Minute Walking Isochrone From Current School Site
75. The population within a 5 minute walk of the current school is 529 people. The population within a 10 minute walk of the current school is 975 people.
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76. NCN Route 12 routes along Dellsome Lane, Parsonage Lane, Knolles Crescent, Pooleys Lane and Dixon Hill Road, and connects Enfield North in London to Spalding vis Stevenage.
77. The nearest bus stop to the site is ‘Dellsome Lane’, this stop is located on Dellsome Lane, circa 190m from the existing school site.
78. The ‘Travellers Lane’ bus stops are served by services 200, 230 and 312.
79. Welham Green rail station is located approximately 1,000 metres east of the existing school site.
80. A summary of the rail services from Welham Green rail station is shown in Table 2.
Table 2– Rail Services from Welham Green Rail Station
Destination Frequency Journey Time Welwyn Garden City 20 mins 9 mins Brookmans Park 20 mins 3 mins Hatfield 20 mins 4 mins
Proposed School Site
81. The proposed school site would be located on existing farm land to the south of Dixons Hill Road. The school site is located adjacent to three sites, which have been identified as favourable development sites for housing.
82. The proposed site would be served by good quality pedestrian routes, and be well connected to the proposed development sites and the existing urban fabric of Welham Green. The 5 minute and 10 minute walking isochrones from the proposed site are shown in Figure 12 and Figure 13 respectively.
83. The existing pedestrian facilities within the vicinity of the site comprise of a footway on the north-eastern edge of Dixons Hill Road. This lit footway is in good condition and of sufficient width to comfortably accommodate pedestrian movement. Dixons Hill Road provides a link to Dellsome Lane and Station Road and access to local facilities including bus stops.
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Figure 12 – 5 Minute Walking Isochrone From Proposed School Site
Figure 13 – 10 Minute Walking Isochrone From Proposed School Site
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84. The population within a 5 minute walk of the proposed school is 260 people (excluding people living in the proposed development sites adjacent to the school). The population with 10 minute walk of the proposed site on the same basis is 1,108.
85. National Cycle Network (NCN) Route 12 runs to the west of the site, within close proximity of the school (approximately 200 metres). NCN Route 12 routes along Dellsome Lane, Parsonage Lane, Knolles Crescent, Pooleys Lane and Dixon Hill Road, and connects Enfield North in London to Spalding vis Stevenage.
86. The nearest bus stop to the site is ‘Knolles Crescent’, this stop is located on Dixons Hill Road, circa 120m from the proposed school site.
87. ‘Knolles Crescent’ bus stop is served by services 200, 230, 305 and 312.
88. Welham Green rail station is located approximately 1,000 metres north-east of the proposed school site.
89. A summary of the rail services from Welham Green rail station is shown in Table 3.
Table 3– Rail Services from Welham Green Rail Station
Destination Frequency Journey Time Welwyn Garden 20 mins 9 mins City Brookmans Park 20 mins 3 mins Hatfield 20 mins 4 mins
Current School Location v Proposed School Location
90. Overall both the proposed and existing school sites are in sustainable locations within walking and cycling distance from local residential areas and sustainable transport networks.
91. Both sites have good pedestrian and cycling facilities within the vicinity of the site enabling easy access from Welham Green to both sites.
92. The proposed school site is located only 120m from the nearest bus stop compared to 190m at the existing school site and both the sites are located 1km from Welham rail station.
93. The existing school site has a total 529 people living within a 5 minute walk of the site, compared to 260 people for the proposed site. However, the number of people living within a 10 minute walk is higher from the proposed site, with 1,108 people living within a 10 minute walk for the proposed school site compared to 975 people for the existing school site.
94. In conclusion, both sites are accessible to significant catchments, and within easy walking and cycling distance for most residents of Welham Green. Both sites have comparable levels of public transport accessibility, and there is not a material difference in the accessibility of each site by sustainable transport.
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Development of Current School Site
95. We understand, that should a decision be taken to relocate the current primary school, the current primary school site would have the capacity to accommodate up to 20 dwellings.
96. To understand the potential impact of this a residential trip rate has been derived from TRICS. TRICS is an industry-wide recognised database containing trip rate information, and interrogating the TRICS database to calculate trip rates by land use represents an established and accepted methodology. It is widely used as part of the planning process by both developer consultants and local authorities.
1.1 To calculate residential trip rates for the current school site the following parameters have been set:
• Land Use: Residential; • Region / Area: UK excluding Greater London and Ireland; and • Location: Suburban.
97. Table 4 summarises the vehicular trip rates. Full detail of the TRICS assessment are contained in Appendix A.
Table 4 – TRICS Vehicle Trip Rates
Arrivals Departures Totals AM 0.235 0.588 0.823 PM 0.405 0.369 0.774
98. Applying the vehicle trip rates as summarised in Table 1 to the development of circa 20 dwellings results in a total number of vehicle trips as summarised in Table 5.
Table 5 – Total Vehicle Trips
Arrivals Departures Totals AM 3 7 10 PM 7 4 11
99. Notwithstanding the potential reduction in the total number of vehicle trips summarised in Table 5 to take account of the sustainable transport initiatives which could be introduced to support development in Welham Green, the assessment demonstrates that an additional 20 dwellings will have no material impact on the transport network and will not effect the modelling and assessment work which has already been undertaken.
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Appendix A
Scenario 1 Without Mitigation – AM Peak – Link Volume to Capacity Ratio
Scenario 1 Without Mitigation – AM Peak – Node Delay Plots
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Scenario 1 With Mitigation – AM Peak - Link Volume to Capacity Ratio
Scenario 1 With Mitigation – AM Peak - Node Delay Plots
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Scenario 2 Without Mitigation – AM Peak - Link Volume to Capacity Ratio
Scenario 2 Without Mitigation – AM Peak – Node Delay Plots
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Scenario 2 With Mitigation – AM Peak – Link Volume to Capacity Ratio
Scenario 2 With Mitigation – AM Peak – Node Delay Plots
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Scenario 1 Without Mitigation – PM Peak – Link Volume to Capacity Ratio
Scenario 1 Without Mitigation – PM Peak – Node Delay Plots
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Scenario 1 With Mitigation – PM Peak - Link Volume to Capacity Ratio
Scenario 1 With Mitigation – PM Peak – Node Delay Plots
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Scenario 2 Without Mitigation – PM Peak - Link Volume to Capacity Ratio
Scenario 2 Without Mitigation – PM Peak – Node Delay Plots
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Scenario 2 With Mitigation – PM Peak – Link Volume to Capacity Ratio
Scenario 2 With Mitigation – PM Peak – Node Delay Plots
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Scenario 1 Without Mitigation – AM Peak - Link Volume to Capacity Ratio and Node Delay Plots
Scenario 1 With Mitigation – AM Peak - Link Volume to Capacity Ratio and Node Delay Plots
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Scenario 1 Without Mitigation – PM Peak - Link Volume to Capacity Ratio and Node Delay Plots
Scenario 1 With Mitigation – PM Peak - Link Volume to Capacity Ratio and Node Delay Plots
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Scenario 2 Without Mitigation – AM Peak - Link Volume to Capacity Ratio and Node Delay Plots
Scenario 2 With Mitigation – AM Peak- Link Volume to Capacity Ratio and Node Delay Plots
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Scenario 2 Without Mitigation – PM Peak - Link Volume to Capacity Ratio and Node Delay Plots
Scenario 2 With Mitigation – PM Peak - Link Volume to Capacity Ratio and Node Delay Plots