Bromley Town Centre Transport Strategy Supporting the Area Action Plan Evidence Base Produced on behalf of London Borough of Bromley by Peter Brett Associates LLP April 2009 Bromley Town Centre AAP Evidence Base Evidence Base We print on 100% recycled paper from sustainable suppliers accredited to ISO 14001. X:\Evidence_Base_290509_FINAL.doc ii Bromley Town Centre Transport Strategy supporting AAP Evidence Base 1 Introduction 1.1.1 The development of the AAP and Bromley Town Centre Transport Strategy has been progressively informed by modelling and strategic study work. This note describes the work undertaken and conclusions reached which have been encompassed within the AAP and Transport Strategy. 1.1.2 As part of developing the evidence base, modelling work was undertaken by Hyder in 2006 and 2007 (which culminated in the modelling runs of Spring 2007) to examine the town centre wide impacts of the development options being considered for the various opportunity sites at that time. 1.1.3 Subsequently the Hyder modelling and trip generation has been reviewed by Savell, Bird and Axon (SBAx) in 2008, to take into consideration the revised quantum of development that emerged through the AAP proposals including the Site G proposals. The modelling took into account the emerging Transport Strategy including changes to the provision and management of parking, as well as improvements to public transport, walking and cycling within the town centre. Mitigation measures such as junction improvements at Mason’s Hill have also been assessed. The development quanta considered as part of this process are given in Table 1. Table 1: AAP Development Quanta Land Use Modelling Spring 2007 Modelling 2008 (Hyder) (SBAx) Residential (units) 1640 2050 Office (sq m) 9000 7000 Retail A1 GFA (sq m) 25500 42000 Retail A3-5 GFA 9sq 9500 7500 m) Community (sq m) 3000 2000 Leisure (sq m) 4000 4000 Hotel (rooms) 250 250 Health (sq m) 1000 1.1.4 The two stages of modelling work have been supplemented by further strategic study work undertaken by PBA. Taken together the modelling and strategic study work has informed the preparation of the Transport Strategy which underpins the proposals in the AAP. 1.1.5 This report provides a summary of the work undertaken by Hyder and SBAx and the further strategic study work undertaken by PBA that underpins the AAP Transport Strategy. The report therefore forms the evidence base for the Transport Strategy and consists of the following sections: Section 2 summarises the work undertaken by Hyder in 2006 and 2007; Section 3 summarises the work undertaken by Savell, Bird and Axon in 2008; X:\Evidence_Base_290509_FINAL.doc iii Bromley Town Centre Transport Strategy supporting AAP Evidence Base Section 4 examines the peak hour development trips and how these have been refined since 2007. It also discusses the retail trip estimation and parking underutilisation; Sections 5 and 6 examine the proposed mitigation measures that will be implemented to ensure that the target for a ten percent reduction in traffic levels by the end of Phase Two (“ten in ten”) is met. Section 5 deals with Parking policy and Section 6 looks at travel plan measures; Section 7 discusses the effect of the revised development trips on the highway network, and changes to mode split; Section 8 discusses the targets set for the AAP and how they relate to the trip generation; Section 9 provides a conclusion summarising the work undertaken and how this has informed the development of the Transport Strategy. X:\Evidence_Base_290509_FINAL.doc iv Bromley Town Centre Transport Strategy supporting AAP Evidence Base 2 Hyder Traffic Modelling 2.1.1 In 2006 and 2007 Hyder undertook extensive modelling using the Paramics micro simulation model of Bromley Town Centre on behalf of LB Bromley and Transport for London. This modelled the development quantum at this time, which is set out in Table 1. The modelling work is described in a suite of reports which provide the results of runs in 2006 and 2007 (Appendix A) 2.1.2 The development trips used in the model were provided by PBA. To calculate the trip generation a managed approach was adopted assuming that the existing underutilisation of some town centre car parks can be used to serve the new developments. It was also assumed that car parking provision would be constrained to the maximum levels as in the UDP standards of that time. 2.1.3 Trip generation figures not taking into account a ‘managed approach’ would have been calculated from the trip databases (TRICS or TRAVL) recognising that there would be a tendency for the usage of the generous parking provision to reflect past trip making profiles for individual sites. This approach involves multiplying ‘typical’ trip rates by the GFA of the development. It would not however reflect the potential for the parking to serve the town centre as a whole and linked trip making within the town centre. This could therefore lead to an overestimation of the additional flows to the new development. 2.1.4 For the ‘Managed Approach’ trips were calculated from trip rates derived from current usage of Bromley town centre car park spaces. This approach was adopted in preference to using rates based on individual sites. Using trip rates based on the usage of existing spaces provided a robust approach which accords with the current pattern of flows into the town centre car parks. 2.1.5 For other non-retail developments proposed in the AAP, typical trip rates were selected from databases that are appropriate for developments located in areas of high public transport accessibility. 2.1.6 The total trips calculated for the new developments were added to the 2004/05 base case flows, and the total flows used in the modelling examined the overall traffic impacts of the development proposals. This approach therefore did not take account of traffic flows into the town centre in previous years, prior to the closure of two large departmental stores, which would have been higher than the base case flows. 2.1.7 The inputs to the modelling therefore assumed that trip making reflected current patterns of movements for the development scenarios based on parking provision for the new developments which accord with the maximum levels given in the recently adopted revised UDP standards. These levels take account of the high public transport accessibility within the town centre. 2.1.8 The modelling approach did not consider the impact of potential changes to general traffic levels in Bromley during the time horizon of the AAP or whether further policy led initiatives X:\Evidence_Base_290509_FINAL.doc 1 Bromley Town Centre Transport Strategy supporting AAP Evidence Base could further influence the quantum of traffic generated by the proposed developments. 2.1.9 The modelling undertaken by Hyder considered the impact of development scenarios from higher levels of retail floor space (49,500 sqm) through to lower levels (25,500 sqm), with different assumptions tested on the phases for development. 2.1.10 The AAP development process was taken forward in an evolutionary way with modelling considering the traffic impacts of development sites and additional parking being placed at various locations. The modelling assisted in demonstrating that the traffic impacts of placing further larger scale retail development and associated parking in the north of the town centre were unacceptable. This led to examining the potential of placing the major retail expansion in the south of the town and at the Pavilion site. 2.1.11 The primary conclusion of the modelling was that only a very modest increase in retail was possible without the need for mitigation measures. It would be possible to accommodate about half of the original 50,000 sq. m (GFA) planned expansion development, but only with widening of the A21 on the approaches. Further mitigation measures were also modelled involving traffic management measures such as further adjustments to signalling, physical changes such as lane allocation at junctions, and changing signal priorities. In order to avoid junction operational problems at Bromley South, the modelling at that stage also assumed that the bus gate at the Elmfield Road/ A21 Kentish Way junction be removed to enable traffic to access the proposed Site G development car park directly from this junction with the A21. 2.1.12 These measures relieved some of the congestion problems but the modelling showed significant delays still occurring on the southern approaches to the town centre. These delays tend to create a ‘ripple’ effect with queuing building to cause congestion problems at junctions along the A21 through the town centre. The traffic modelling showed network delay substantially increased even for development scenarios incorporating the lower levels of retail development. 2.1.13 The further highway mitigation measure involving widening of the A21 to two lanes each way between Kentish Way and Bromley Common when considered for the lower levels of retail floor space was shown to largely reduce congestion back to base levels. The test employed was one of ‘nil detriment’, in other words whether mitigation measures can return traffic delays to base levels. 2.1.14 The modelling therefore showed that with reliance placed on highway and traffic management measures alone, retail development of up to 25,500 m 2 GFA could be accommodated. This would require substantial highway mitigation works including the widening of the A21 southern approaches. The modelling also indicated that some problems remain at particular junctions and there are some further delays above base levels on certain bus routes. Hence further traffic management measures, particularly bus priority measures to protect and enhance service provision would also be needed to accompany the mitigation measures that have been modelled.