Praxilab - Individual Public Transport System

by Michel Parent

On May 16, 1994, INRIA, announced the opening of the Praxilab research laboratory at Rocquencourt, south west of Paris. The laboratory is part of "Praxitèle", an R&D programme being jointly developed by "Compagnie Générale des Eaux" subsidiary "CGEA", "Dassault Automatismes et Télécommunications", "EDF", the INRETS national transport safety research institute, "Renault" and INRIA. Praxitèle has been set up to develop and test a new individual public transport system based on self-service small electric vehicles.

Work on the new transport system was officially launched in May 1993 and it is scheduled for field trials in 1995 at St. Quentin en Yvelines, near Paris.

INRIA already has several vehicles at its Praxilab laboratory and research on these has just commenced aimed at automating vehicle motion, the initial aim being low-speed driverless movement.

To automate the vehicles, INRIA commissioned a series of computer driven electric vehicles based on a Ligier model from Aleph Technologies. A VMF 68040 on-board computer controls the electric power source (and therefore vehicle acceleration), as well as braking and steering functions. It also receives data from a variety of internal sensors for speed, wheel encoding, brake-circuit pressure, steering angle etc., and from external sensors such as a video camera or ultrasound sensors.

Prototypes of computer driven electric vehicles based on a Ligier model

One of the external sensors, specially developed by Praxitèle from an INRIA patent, provides researchers with high-rate acquisition (ie. 500 Hz) of the relative position of the preceding vehicle. This has two intended applications. The first is to assist riving in a line of vehicles with the shortest possible distance between them, eg, about four meters at speeds of 50 km/h. In this configuration, the sensor uses a linear camera linked to a special optical device, and seeks special infra-red beacons locatd on the rear of each Praxitèle vehicle. The second application concerns automatic driving in traffic jams. A vehicle equipped with this sensor could "latch onto" any vehicle in front of it by lighting up the leader's rear reflectors with infra-red flash emitted at a predetermined rate.

Initially, automatic driving techniques will make it possible to marshall trains of empty vehicles driven by a single operator in order to distribute the empty vehicles around the available car parks. In time, these technologies will enable users to aligh from a vehicle on arrival at their destination (eg, a station, a shopping mall, or a company) and allow the vehicle to park itself in the nearest drop-off area, or even in an underground car park. Thereafter, INRIA is interested in automatic driving with or without passengers in dedicated vehicle lanes linking distant sites.

At its Rocquencourt facility, INRIA is also carrying out research into the modelling and performance evaluation of this new transport system. Questions being asked involve the conditions required for high performance with such systems and whether they can deliver a worthwhile service to the community. Dynamic fleet management techniques are also being studied in order to minimise movement of empty vehicles. Ongoing research in this area covers mathematical methodology and computer simulations for transportnetworks and their optimisation. In the near future, it will be enriched with data base covering the description of the urban areas to be so equipped.

Please contact:
Michel Parent - INRIA
Tel: +33 1 39 63 55 93