Design and Testing of a Pedestrian Alert System (PAS) (2002)

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 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 
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.