A new, comprehensive, congestion measure for freeways

The purpose of this study is to develop a new and objective measure to evaluate freeway congestion. Congestion has yet to be consistently defined because it impacts on choices regarding investments in infrastructure. A new measure, termed the Critical Occupancy Point (COP), is developed. COP evaluates the change in occupancy vs. speed and defines the point where congestion begins. COP may be developed from data which is readily available from each freeway sensor. Data analysis from a freeway in Israel shows that each segment provides different congestion characteristics and consequently a different COP. The COP measure identifies recurrent and non-recurrent congestion and the breakdown before it actually occurs. The COP and the speed at which it occurs are found to be distributed normally. Furthermore, it was found that the volume at which the COP happens increases as the distance from the previous entrance increases.