Planning an integrated public transport network

In order to provide a viable alternative to the car, bus and rail services should be planned to take account of the interchange between modes

It is not uncommon that planning of public transport networks is carried out on a uni-modal basis, with bus and rail planners not considering the other mode in detail when creating timetables and routes.

Analysis of NTS (2017-2019) data however shows that there is considerable interaction between the modes, with almost 1 in 5 trips involving  a rail leg also having a bus leg for either access or egress. It also shows that  60% of commuters who normally travel by car would find it difficult or very difficult to complete the same journey by public transport.

Shravan Patel and David Aspital will both be speaking at Modelling World on 2-3 November, Birmingham

Therefore in order to provide a viable alternative to car, it is necessary for bus and rail services to be planned to take account of the interchange between modes and ensure this is as frictionless as possible.

This must be done in a manner that takes account of the strengths and weaknesses of both modes. Local bus services provide a level of flexibility that is simply not possible with rail to change routes and timetables based on changing customer needs. Unlike rail, buses also do not require costly and lengthy infrastructure upgrade programmes if extensive alterations are needed.

Rail, meanwhile, is much more competitive with car in terms of journey time, especially for longer distance trips, but without local bus services may be inaccessible to many who either  do not live within a walkable distance of the nearest rail station or do not own a car and therefore cannot park and ride..   

Planning of such an integrated public transport system necessitates analysis and modelling that considers both modes at the same time.

The Strategic Rail Analysis Model (SRAM)

The Strategic Rail Analysis Model (SRAM) developed by Network Rail is a model, implemented using PTV Visum, of all rail services across Great Britain with detailed platform-level timetable data and allocation of passenger demand to these services across the day.

This has been combined with timetable data freely available from the Bus Open Data Service (BODS) which contains route and service information for all buses across the country on a daily basis.

The bus and rail networks have been merged together to allow for transfers between the two modes meaning that the model can be used to analyse full end to end journeys and in particular highlight areas where the bus and rail timetables may not align with each other and passengers would have high transfer waiting times.

Alternative timetable options are being explored and appraised to reduce these waiting times and ensure the best experience for passengers on popular routes.

This model is also being used to assess the needs of passengers who may have additional requirements, for example step-free access.  Information for each station that categorises whether it has step-free access or not has been imported into the model and therefore the difference in passenger experience is calculated, for example if a longer or less frequent bus leg is required to access a rail station with step-free facilities. 

The national scale of the model allows for consistent analysis and comparison on the same basis regardless of the area of interest. The model also has the capability to layer in local data to provide a further level of richness to the analysis and tailor it to the use case of a local authority.

It also means that the benefits  of large-scale infrastructure improvements that may have impacts across the network can be tested, and these benefits can be fully realised by ensuring that the local facilities that enable the rail journeys are in place. 

This is the first time that such a multi-modal tool is available to Network Rail as part of its business as usual analysis and enables planning of a public transport system that offers a viable alternative to car at a time when it is needed more than ever.

Shravan Patel is Crowding Analysis Manager, Network Rail and David Aspital is a Senior Modeller at PTV Group