Technical Note Project: Hertfordshire County Council Transport Job No: 60427260 Planning Contract Subject: East of Stevenage Development Test - Transport Modelling Report 2015 Revision 1 Prepared by: Paula Paez Date: 14th May 2015 Reviewed by: Abi Finch Date: 15th June 2015 Approved by: Edmund Salt Date: 16th June 2015 1.0 Introduction In April 2015 AECOM was asked by East Hertfordshire District Council (EHDC) to look at future transport issues in response to a proposed housing development to the east of Stevenage. The aim of this assessment is to identify the potential local transport related issues that may arise as a result of the East of Stevenage housing development proposal and provide sufficient mitigation proposals if necessary. The assessment has been carried out in conjunction with Hertfordshire County Council (HCC) so that in addition to the East of Stevenage development, the assessment also includes explicit consideration of impacts of the latest North Hertfordshire District Council (HNDC) and Stevenage Borough Council’s (SBC) housing development assumptions. The East of Stevenage development proposal has been modelled as a Do Something scenario, making use of the latest Stevenage & Hitchin Urban Model (SHUM), a transport model that was updated in January 2014, and approved by Highways England in March 2014. This technical note serves three key purposes: x Firstly, to explain the stages undertaken during the forecasting of the highway model assignment including the development of the future year highway network and traffic demand, including housing developments forecasts (Section 2 to 5). x Secondly, to present details of potential transport issues on the highway network in the Do Something housing development scenario (Section 6). x Thirdly, to discuss the need for mitigation, in response to the transport issues of the housing development scenario (Section 7). This assessment focuses primarily on the local road network to the east of Stevenage in the SHUM model area shown in Figure 1. 2.0 Background SHUM covers Stevenage and some of the North Hertfordshire area (primarily Hitchin, with elements of Letchworth included). It was originally developed by AECOM in 2009 and subsequently updated in October 2011 following a review and advice from Highways England. SHUM was originally developed to assist the preparation of the Hitchin and Stevenage Urban Transport Plans (UTP) and is validated to a 2008 base year against observed traffic count data and journey times. Highways England signed off the 2008 base year model (October 2011 version) on 8th December 2011. Using SHUM in forecasting mode seeks to determine the impact on the future transport network as a consequence of shifting patterns of demand over time, and forms the basis of the forecasting and analysis of the housing development proposal. The forecasting methodology for SHUM has been reviewed on two occasions by Highways England, who has provided advice on the approach and use of SHUM as a tool for forecasting. Where Page: 1 of 61 P:\UKBHM2-TP\TP\PROJECT\Transport Planning - Hitchin Urban Transport Plan\22- East of Stevenage Testing\Reporting\Report\TN- East of Stevenage Development Test Modelling Report 2015_Rev1.doc Technical Note appropriate, this advice has been incorporated into an update to the SHUM forecasting model; the most recent update was in January 2014 and signed off by Highways England in March 2014. Details on Highways England’s reviews and subsequent forecasting model updates can be found in the SHUM Forecasting Model Update Report, issued January 2014. The East of Stevenage development assessment needs to evaluate the peak hour traffic impacts on the local and strategic road network, associated with the development. In this context, the 2031 SHUM model was assigned for the AM peak (08:00-09:00) and PM peak (17:00-18:00) periods. 3.0 Network Development This section discusses the extent of the future year highway network, including constructed and committed infrastructure. As discussed, the basis for the model forecasting was SHUM, which covers Hitchin and Stevenage, and the A1(M) motorway including junctions 7,8, and 9. The North Hertfordshire towns of Letchworth and Baldock are on the periphery of the model area but the model does not extend as far as the town of Royston. The extent of the highway network is shown in Figure 1. Figure 1: SHUM Highway Network Page: 2 of 61 Doc. F8/10 P:\UKBHM2-TP\TP\PROJECT\Transport Planning - Hitchin Urban Transport Plan\22- East of Stevenage Testing\Reporting\Report\TN- East of Stevenage Development Test Modelling Report 2015_Rev1.doc Technical Note 3.1 Future Year Do Minimum Highway Network SHUM was validated to reflect the transport network operation in 2008. To provide a representative transport network for 2031, the highway network was updated in 2012 to include the constructed and committed transport improvements in the study area. This resulted in the development of the Do Minimum network for 2031 which included the following identified improvements which were anticipated to be operational by 2021: x Hitchin Payne’s Park gyratory pedestrian crossing; x Glaxo Smith Kline junction improvements; and x A1(M) Junction 7 signalised junctions. It should be recognised that this assessment has not included the impact of the A1M junction’s 6-8 Smart Motorway proposal, which can now be considered a committed scheme. This would need to be included in any future assessments. 3.2 Future Year Scenarios Highway Network The proposed East of Stevenage development is on the eastern edge of the SHUM model, on the boundary between Stevenage Borough and East Hertfordshire District Council. The development will be located to the east of Gresley Way between the B1037 Stevenage Road and Lanterns Lane (Figure 2). Gresley Way and key local junctions specified for assessment by the client are all included within the model network, however the model coverage does not extend in detail to the east of the development site therefore the model is not capable of evaluating the impact of the development within the East Hertfordshire area. The model can however identify the increase in flows on the A602 and through Aston. Figure 2: East of Stevenage Development Area The developments trips have been added into SHUM zone 5116 which the development area is fully contained within (see Figure 3). Page: 3 of 61 Doc. F8/10 P:\UKBHM2-TP\TP\PROJECT\Transport Planning - Hitchin Urban Transport Plan\22- East of Stevenage Testing\Reporting\Report\TN- East of Stevenage Development Test Modelling Report 2015_Rev1.doc Technical Note Figure 3: SHUM Zone System Existing Access Points Development Access Points Two new connectors have been added to the zone to represent the two proposed development access points. Access point 1 will join the existing Uplands / Gresley Way priority junction and will be converted to a roundabout. This junction and the Uplands did not exist in the SHUM network therefore a new junction has been added in and in order to assess the suitability of the roundabout arrangement a new spigot link connected to zone 2114 to the west has been coded to represent the Uplands arm. Uplands is not a through road so coding this link may result in an under/over representation of traffic at the roundabout as all traffic from zone 2114 will be provided with an alternative loading point that in reality would not be available to all. This will be a departure from the Highways England approved SHUM base and forecasting models. As a check a Select Link on the zone has been run to ensure a reasonable amount of traffic is entering and exiting the zone via Uplands (please refer to Section 5 for the Select Link results). Access point 2 will join the existing White Way/ Gresley Way priority junction and be converted to a roundabout under the development proposal. In order to maintain consistency with previous SHUM modelling work there is a third loading point for zone 5116 to the north which joins onto the Stevenage Road. In practice this would not be a vehicle access point for the development and therefore the trips the model allocates to this route would in reality come out of the new access opposite Uplands and would be less likely to use Stevenage Road. 4.0 Demand Development An important part of forecasting the likely traffic conditions on the highway network includes understanding changes to travel demand. Demand changes are a reflection of changes in income, transport prices, demographics and land use changes. The methodology employed for developing the demand matrices for the 2031 future year assessment can be broken down into four stages, discussed below: Page: 4 of 61 Doc. F8/10 P:\UKBHM2-TP\TP\PROJECT\Transport Planning - Hitchin Urban Transport Plan\22- East of Stevenage Testing\Reporting\Report\TN- East of Stevenage Development Test Modelling Report 2015_Rev1.doc Technical Note x Stage 1 – Development of background growth factors for internal to internal (within the modelled area) and internal to external trips. Background growth effectively represents growth brought about by general changes in economic conditions resulting in increases in wages, changes in fuel prices etc., essentially all those elements not related to development. These factors were derived using the National Trip End Model (NTEM) forecasts and TEMPRO. The latest version of the dataset, NTEM 6.2 was used in conjunction with the current version of TEMPRO 6.2. This ensured the forecasts benefit from nationally and locally derived growth projections in accordance with government guidance. For external to external movements, the East of England Regional Model (EERM v3.1) forecasts were used to provide growth factors. The growth factors were applied to the 2008 calibrated SHUM base year demand through a Furness process. x Stage 2 – Collection and assessment of development information in the area is undertaken to calculate the number of trips that specific developments can be expected to generate.