Field Testing of a Pedestrian Alert System (PAS)

Charles Rodgers and Richard Blomberg

Abstract:	The Federal Highway Administration (FHWA) is seeking to develop a system to alert automotive drivers to an impending collision with a pedestrian. Under contract to FHWA, the authors designed, simulated, and field tested a prototype PAS that relies on DGPS techniques to accurately determine relative position and velocity measurements, which allows the prediction of collision probabilities, and activation of an appropriate driver alert. A US patent has been issued for the PAS developed in this effort. The key requirements of the system include providing accurate warnings with a low false alarm rate at least three seconds before the collision, all weather functionality, and the capability of detecting pedestrians hidden by visual screens. It minimizes false alarms through a variable warning zone" that depends on vehicle and pedestrian motion. It also is capable of alerting the pedestrian in danger. The PAS design is compatible with Intelligent Transportation System (ITS) and telematics equipment. Most vehicles sold in the future will have a GPS, a processor, and eventually an ITS wireless data link in their telematics, which will minimize the PAS equipage costs. The PAS has both pedestrian and vehicle modules, each containing a low power, GPS receiver capable of weak signal tracking, and a low cost/power, radio transceiver. The vehicle module is intended to be part of an enhanced vehicle navigation system and the pedestrian module could be integrated with cell phones or other personal electronic devices routinely carried by pedestrians. The pedestrian module broadcasts its position and velocity information to all vehicles in range with no personally identifying information. The vehicle module receives the information from the pedestrian and determines the relative distance and velocity to the pedestrian. The vehicle unit calculates a "warning zone" based on its velocity vector, the state of turn signals and transmission, and the velocity of the individual pedestrian. If the pedestrian is predicted to be in the warning zone and the time-to-collision is within a critical time (on the order of 6 seconds), the driver receives an alert. The alert provides information on both the urgency and direction of the threat. The most challenging aspects of the hardware design were the radio link, driver alert implementation, and the engineering of the small pedestrian module that could be worn by a person that would provide more than 24 hours of protection between recharges. Meeting the power consumption goal required developing elaborate conservation techniques including millisecond control of the operation of the RF transceivers and the GPS receiver. The real-time application software for the pedestrian module is embedded in the GPS receiver, while the vehicle module uses an external single board computer to host its real-time software. The radio link must allow unlicensed transmitters but provide high integrity communication over distances sufficient for GPS acquisition and tracking before the point of closest approach, while maximizing battery life. The driver alert must be interpretable in an instant with little training and it must not cause a dangerous reaction from the driver. The design and development of the PAS was recounted in earlier ION papers. This paper describes the field testing of the final system. This testing included: • the human factors of the driver alert presentation • the capacity, range, and robustness of the radio link • the accuracy and integrity of the relative DGPS positioning between vehicle and pedestrian • the discrimination, accuracy, and integrity of the collision predictions. The completed testing indicates that the system is capable of providing a significant contribution to the goal of reducing the death and injuries caused by vehicle collisions with pedestrians. It also could be adapted for bicycle safety, as well as airport ramp and construction site pedestrian safety."
Published in:	Proceedings of the 2008 National Technical Meeting of The Institute of Navigation January 28 - 30, 2008 The Catamaran Resort Hotel San Diego, CA
Pages:	549 - 560
Cite this article:	Rodgers, Charles, Blomberg, Richard, "Field Testing of a Pedestrian Alert System (PAS)," Proceedings of the 2008 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2008, pp. 549-560.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In