The Influence of Crashes on Network-wide Flow-Density Relation

This research compares flow-density relationships of a major urban freeway network in Chicago, Illinois during peak hours with and without reported crashes for the years 2007 – 2010. Currently, there is a long delay in getting information about a crash to drivers approaching a crash site. This leads to congestion as approaching vehicles are unaware of the crash ahead. The correlation between the time or location of a crash on a network and the shape and distribution of the resulting flow-density diagram can be used to understand the areas within the transportation network that will be eventually affected by specific crashes. Once these relationships are defined, then ITS technologies including CV with V2V and V2I communications can be used to send messages to drivers headed in the direction of the crash and alert Emergency Medical Services sooner. This will allow drivers to redirect their routes to avoid the crash site and overall, reduce congestion. Major differences were found in the flow-density diagrams between peak hours with and without reported crashes on the network. This research suggests relationships between the spatial distribution of crashes and the resulting flow-density diagrams. Future work involves obtaining more data to define a more distinct relationship and simulating the same network with CV at different market penetration rates on similar days to study the effects on the resulting flow-density diagrams