Transport demand management, often known as TDM, is the application of strategies and policies to reduce travel in single-occupancy private vehicles - or to redistribute it to places and times where it causes fewer negative externalities such as congestion or pollution. (See Demand Management)
Managing demand can be a cost-effective alternative to increasing capacity, and also has the potential to deliver better environmental outcomes, improved public health and more liveable and attractive cities. A major tool to implement TDM is the Travel Plan, which may be site-based, organisation-based or area-based.
Whilst many of the techniques of transportation demand management, and therefore of travel plans, involve non-technical approaches such as personal coaching and the design and production of printed material, ITS applications can play a major role in three areas:
Car-pooling, one form of this concept, also has urban planning benefits, in that building developers can be required (or choose) to provide fewer parking spaces, so saving land and costs.
A general source of expertise about TDM worldwide is the Victoria Transport Policy Institute (VTPI) in British Columbia, Canada (http://www.vtpi.org). There are also a number of national and regional organisations that are involved in the promotion and / or management of schemes designed to support TDM. These range from organisations promoting TDM itself, such as ACT TravelWise in the UK (http://www.acttravelwise.org), through to organisations promoting particular elements of travel demand such as Carplus in the UK. Carplus was established to support the development of car clubs and ride-sharing schemes in Britain. Its core stakeholders were operators, service providers and local authority partners.
Local authority membership of these organisations can help them achieve their targets in areas which TDM can address - such as congestion, air quality and social exclusion.
Another important group of organisations is the providers of software for matching journeys. These include companies producing scheduling applications - who may also provide applications specific to scheduling para-transit services. There are also companies who produce software for particular service markets which involve flexible operations – such as firms producing software for the taxi market and software providers for the delivery of travel plans.
For ITS-based ride-sharing, potential users contact a control centre to specify their destination, preferred time of travel, and any special needs. The centre uses algorithms to identify the most appropriate vehicle operating that matches requirements as closely as possible. The vehicle could already be carrying passengers on compatible routes. It may be privately owned (such as a car) with the private owner simply giving a lift to the passenger - or it may be a larger vehicle, perhaps a shared-ownership one. It may be a one-off or a regular journey. The dispatch may be carried out automatically or arranged through a website - perhaps involving an element of social networking.
Often the service will be provided to a specific client group, for instance the elderly, and users will already have registered with the operators or with a service provider who has contracted the operator.
The service will use specific software which is in many cases capable of handling a very large number of different types of enquiry and delivering solutions consecutively.
Implementers should consider the ease of use of the software, its appropriateness for providing transport for particular client groups with very specific requirements - and the extent to which it is scalable. They should also consider the extent to which it allows integration with other Travel Demand Management solutions.
This is an area where web-based and cloud-based technologies are increasingly coming to the fore.
Whilst ride sharing and matching software can offer huge increases in the efficiency of ‘informal’ shared transport services in developing economies, the cost of the required software will be a barrier to implementation. Possibly more important is the extent to which the informal sector can be controlled by the regulator or authority – impacting on the extent to which the software can be used in practise. Institutional issues will need thorough analysis before the introduction of these systems is contemplated.
Dynamic Routing or Scheduling is closely related to Ride Sharing and Matching, in that it often uses the same or linked software and is often employed by para-transit services so that routes can be calculated in real-time to enable ride matching to take place.
The software requires digital maps of the road network, including one-way sections and restricted turns. These need to show road widths and restrictions so that the system can calculate the shortest appropriate routes accurately – and information on road surfaces need to be maintained so that their suitability for different types of public passenger transport vehicle can be assessed.
The service requires in-vehicle devices to guide the driver and links to the control centre where the calculation of ride sharing and matching is performed,
Since schedules are re-calculated in real time - only summary and approximate advance information can be conveyed to waiting passengers. For instance, times may be shown as a ‘time window’ in which the vehicle will arrive, rather than a detailed timing.
Because of the complexity of the tasks undertaken by the software it is very important that agencies and authorities satisfy themselves that the software they are considering purchasing has been used successfully in similar environments to perform similar tasks.
The power of computing is increasing very rapidly and hence the complexity and sophistication of performance of such dynamic routing systems.
Obtaining current and accurate digital maps of the road network can be very difficult. Dual-carriageway roads in cities in developing economies may feature very long barriers between the carriageways which cannot be crossed. At the same time the barriers may be changed quickly – being removed at little or no notice in certain places to allow vehicle manoeuvres which were not previously possible. Systems and processes to guarantee the reliability of digital map data is essential if dynamic routing is to be adopted successfully.