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Report n°6: Urban Public Transport

Improving the indicators to measure the transport offer

Measuring the transport offer is based on several indicators: the simplest one is provided by the number of kilometres travelled by vehicles in commercial service (vehicles x km).

This indicator depends on the length of the lines and the frequency of service. It is clearly perceived by users in so far as it reveals indirectly the intensity of service from their own point of view, that is the interval of time between two vehicles (headway). By relating the number of km travelled to the length of the network, an indicator is obtained which expresses in fact a number of daily runs, which may need to be corrected for the sake of comparison by taking into consideration the amplitude of service between the first and last run during a day. The capacity of vehicles (bus, articulated bus, tramcar) can also be made to enter into the calculation and is arrived at by multiplying the number of kilometres travelled by the number of available seats in the vehicle (seats x km). This indicator may be very pertinent to interpret the results of customer satisfaction surveys because comfort influences the perception of quality, but in that case it must be calculated for each individual line.

In Nantes, for example, the number of seats x km on offer one year before entry into service in 1985 of the first line, was 1.2 million/year. Entry into service of the tramway line led to an increase of only 50,000 seats x km, despite the tramway's high capacity. In 1992, when the second line was opened, the figure was 1.6 million. But several causes combined to arrive at this result: of course the greater number of high capacity vehicles (articulated buses, three-car trams) was one of them, but also the extension of the territory covered and consequently the greater length of lines, which had an impact on the number of kilometres covered. The increased frequency of service at each stop is not therefore directly perceptible.

If one considers that the "network's presence" is expressed above all by proximity to a line and by a short wait, the number of km travelled by km of line seems a better indicator, or else the number of seats x km/km of line. We have used here only the number of kilometres travelled which privileges frequency.

The following tables show, for each network including tramways, the development of the number of journeys per inhabitant and the number of kilometres travelled/km of line.

Table 1. Evolution of some indicators in tramway networks from one year before entry into service to two years later (whole network)

networks

Journeys/inhab before

Journeys/inhab after

Km travelled/km of line before

Km travelled/km of line after

Nantes 110 145 25,13 27,58
Grenoble 98 126 43,95 50,5
Strasbourg 103 130 37,64 41,77
Rouen 67 87 19,69 25,84
Montpellier 90 131 25,51 30,16
Orleans 61 77 18,8 23,68

Table 2. Evolution in %, one year before entry into service and two years after (whole network)

networks

% evolution journeys/inhab

% evolution km travelled/km of line

Nantes 31,8

9,7

Grenoble 28,6 14,9
Strasbourg 26,2 11
Rouen 29,9 31
Montpellier 45,6 18,2
Orleans 26,2 26