Routing Algorithm for Vehicles that Avoids Severe Traffic Accident Hotspots on the Road Network (Using the City of Springfield, Massachusetts as a Case Study)

In [1] statistically significant clusters (hotspots) of severe Traffic Accidents (TA) are found. In this article, as a continuation of [1], a simple routing algorithm to avoid TA hotspots on a road network has been proposed («hotspot avoidance» path). If the road network is represented by a graph with edges and nodes, it is enough to mark every edge which lead to the TA hotspot as «not passable» by letting a attribute of the edge be a very large digit, much greater than max edge length for a given road graph — and the routing algorithm (Dijkstra or Bellman-Ford) will avoid the TA hotspot automatically. Computer simulation was performed for Springfield, MA. It is shown that for the same initial and end points of the route, an average ratio (Route avoiding TA length/Original route length) is bigger for shorter original (without taking into account TA hotspots) routes and gradually slows down to 1.04 for max original route length inside Springfield. Route length ratios show extra route length needed to avoid TA hotspots, but say nothing about new route safety. To estimate safety gain, a new Relative Risk Ratio RRR= (TAs along route which avoids TA hotspots/TAs along original route) was introduced. It is shown for Springfield that relatively short (less than 4 km) original routes are more dangerous (have more TAs along the «hotspot avoidance» route) than original ones, but for relatively long (> 4 km) original routes average RRR gets smaller by 16 % while modified path gets longer by 8 % in average.