pSafety: A Collision Prevention System for Pedestrians Using Smartphone

We implement a collision prevention system, called pSafety, which instantaneously informs pedestrians and drivers of the potential threatening accidents. Unlike other systems, pSafety alerts pedestrians of threatening vehicles coming from not only the line-of-sight, but also non-line-of-sight due to obstructions of the wall corner or other vehicles. pSafety collects GPS information from smartphones of pedestrians and vehicle drivers through mobile networks. The main challenge of pSafety is that current smartphones demonstrate larger distance errors on the order of a few meters due to its intrinsic low-cost GPS receivers. To address the impact of large-error positioning to pSafety, we regard each participant on the map as a sector that indicates a predicted location. We subsequently design the Sector Overlap Detection Algorithm, called SODA, to detect whether two sectors are overlapping in time O(1). To avoid warning fatigue, we additionally provide a threat ranking method to evaluate the degree of risk for each potential collision event. Through our designed App, pedestrians and drivers both could receive a clear view of potential risks and then take proper actions to avoid accidents. In our implementation, we show that pSafety rapidly informs participants (i.e., pedestrians and drivers) and provides each participant a sufficient response time to avoid collision.