The clean air and energy conservation act of December 30, 1996 applied in Ile de France specifies traffic restrictions in central Ile de France (Paris and 22 adjacent municipalities in its closest suburban ring), and free public transportaion during a pollution alert. Last September 30th, the threshold of alert concerning air pollution had been exceeded in Ile de France. The public authorities put the law on alternated traffic into action on October 1st (even-numbered vehicles were not allowed to circulate). Motorists (drivers and passengers) had to change their mobility behaviour. The STP proceeded with an assessment of the effects of this measure on mobility. This assessment was made on the basis of: - data from road and freeway vehicle counting systems, - data concerning public transportation use (Metro, RER-Express Regional Railway Network and Bus), - surveys which analyse the change of mobility behaviour on that day, - a comparison with the journeys on a typical Wednesday in October. This paper covers: (1) the legal act and its enforcement decrees; (2) the results viewed in terms of motor circulation decrease, public transportation use increase, incidences on parking, park and ride use, 2-wheel motor use and walking, carpooling practices changes, even vehicles violating the law; (3) the impact on public transportation operations; the (4) analysis of the resulting complex phenomena: decrease in certain types of journeys, modifications of itineraries, induction of public transportation traffic, multiple adaptation strategies; (5) an economic analysis of the consequences for public transportation companies and the general activities; and (6) evolvement of the operational plans for future actions.
Abstract