Design and Testing of a Pedestrian Alert System (PAS)

Charles Rodgers, Darrell Greenlee and Richard Blomberg

Abstract:	The Federal Highway Administration (FHWA) is seeking to develop a system to alert automotive drivers to a potential collision with a pedestrian. Under a contract to FHWA, OPTIMUS Corporation and its subcontractor Dunlap and Associates conducted an analysis of contributing factors in pedestrian crashes to determine the requirements for the system. Simultaneously, potential sensor, positioning, and communication technologies were assessed. The resulting requirements highlighted the need for a system that can provide high integrity warnings with a low false alarm rate, provide a minimum of three seconds warning, function in all weather, and be capable of alerting drivers to pedestrians hidden by visual screens. After analyzing a number of architecture options, OPTIMUS determined that the system best able to meet the requirements would be based on differential GPS and a low power, short range radio architecture. OPTIMUS then performed feasibility analysis and testing on the PAS concept. The PAS will have a pedestrian module and vehicle module, each containing a GPS receiver. The pedestrian module will utilize the tiny, low power GPS receivers being developed for cell phone integration, and a low cost and power radio transceiver. The pedestrian module will broadcast 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 using DGPS techniques determines the relative distance and velocity to the pedestrian. The vehicle unit constructs a "warning zone" based on its position, velocity, and control settings (transmission, turn signal, etc). It then uses the relative position and velocity data to predict the closest approach or intersection with the warning zone. OPTIMUS validated the concept through field tests that indicate that the architecture can provide the high integrity alert with a low false alarm rate. In the tests, a pedestrian took several angles toward, away, and parallel to a vehicle approaching on a street while GPS data were collected from both the pedestrian and vehicle. The feasibility analysis and testing show that PAS will provide all weather operation, non-LOS operation around visual screens, pedestrian detection at close and relatively long range, the capability for very good threat discrimination to reduce false alarms, a variable "warning zone" depending on vehicle motion and state, the capability to handle forty or more simultaneous pedestrians, an automatic alert not requiring interpretation or attention from the driver, the capability to alert the pedestrian, and alert data in a digital format that can drive any type of user interface visual, audible, or tactile. The PAS also is compatible with Intelligent Transportation System (ITS) and telematics concepts and equipment. Most vehicles sold in the future will have a GPS, a computer, and eventually an ITS wireless data link in their telematics, which will reduce the PAS equipage costs. The paper will discuss the system requirements, architecture, concept of operations, design tradeoffs, feasibility analysis, and DGPS feasibility test results.
Published in:	Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002) September 24 - 27, 2002 Oregon Convention Center Portland, OR
Pages:	409 - 420
Cite this article:	Rodgers, Charles, Greenlee, Darrell, Blomberg, Richard, "Design and Testing of a Pedestrian Alert System (PAS)," Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002), Portland, OR, September 2002, pp. 409-420.
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