INSTITUT Veolia Environnement

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Report n°6: Urban Public Transport

The number of journeys per inhabitant is increased

The most comprehensive indicator to assess the extent of public transport use is the number of trips per inhabitant. In towns which have installed an exclusive right-of-way line, this indicator rises by approximately 30% between the year before entry into service and the second year after entry into service. To fully appreciate the significance of such a development, it needs to be compared to similar conditions in towns where no works of any importance have been undertaken. In the 80s, in towns without projects the increase was 5%, so that the specific effect of the exclusive right-of-way tramway system in Nantes and Grenoble corresponds to a 25% growth. In the 90s, the general context was less favourable, since development was estimated at -3%, so that the tram-based exclusive right-of-way effect in Rouen and Strasbourg is estimated to have been approximately 33%. To define more precisely the exclusive right-of-way effect, account must also be taken of the number of connections, which is higher when construction of the tramway means restructuring all the lines of the network with an increase in the number of the bus lines transferred to feed tramway stops.

The connection rate can be evaluated at 1.2 on a bus network, which means that the number of rides (i.e. one ride in a bus) is greater by 20% than the number of journeys (i.e. a journey from the point of origin to the point of destination, however many vehicles are used to get there). In Nantes, Grenoble and Strasbourg, the rate is 1.3. If one takes into consideration the connection rate, the difference between tram-based exclusive right-of-way networks and "bus only" networks is reduced, since one is measuring the effect on actual journeys rather than on the number of rides.

Naturally, ambitious exclusive right-of-way projects, whether tram or bus-based, have given rise most of the time (but not always) to an increase in transport offers. The relationship between increased use and increased offer is a simple way of defining the efficacy of the offer's reorganisation.