In large urban areas, high-capacity transit and road infrastructure play a crucial role in the spatiotemporal distribution of economic and social activities. In many cities, the subway is the critical component of the public transit system just as freeways form the effective backbone of the road network. In the case of island cities like Montreal, bridges are also essential to the proper functioning of the transportation system as a whole. As such, subways, bridges and freeways can be considered “strategic” transportation infrastructure since the disruption of just one of them has wide-reaching consequences. It is therefore important, from both long-term planning and operational perspectives, for transportation authorities to identify strategic infrastructure and to have good knowledge of its users’ travel patterns.
In Montreal, methods of analysing public transit usage patterns based on travel survey data have long been used for planning and operational financing purposes. However, a similar methodology has yet to be adopted for roads. This paper presents a methodology for thoroughly characterising the users of strategic road infrastructure (bridges and freeways) based on data contained in a large-sample household travel survey. The Montreal travel survey asks all respondents who completed their trip by driving a car which major bridge or freeway was used. The 2008 survey contained roughly 70,000 trips with at least one bridge or freeway declared. Around 60,000 of these declarations could be validated using a constrained trip assignment algorithm applied to a large and detailed network (117,000 links). Adopting a totally disaggregate approach, the algorithm transforms the bridge and freeway declarations into complete itineraries while preserving the socio-demographic attributes of each traveller. These results can be used to analyse strategic road infrastructure from multiple perspectives: the detailed characterisation of the “clientele”, an estimation of their travel consumption, analysis of congestion and road pricing, and the
design of mitigation measures – including alternative public transit options – in the event of closure or failure. An interactive visualisation tool forms the basis of these investigations.
The method is based on a travel survey but could be adapted for emerging passive data sources that provide partial itinerary information such as GPS traces, automatic toll collection systems, mobile device applications and so on.
