The mechanism described above for the 2:1 merge and roundabout
cases can be generalized for local congestion areas. Consider
a localized congestion area which has a small network of roads and
a set of N input/output traffic signal points which dictate the input
and output flow out of this localized area. Based on free flow traffic
theory [43], any free flow road segment can be associated with an
approximate traffic curve as described in earlier examples. Given
that the localized area is a high congestion area, we can assume that
most road segments are used at high capacity even in the presence
of traffic signals. Hence, there is constant flow across different
directions within the localized region. In our local de-congestion
protocol, we explicitly model a localized congestion area with an
approximate traffic curve with a tipping point as specified by the
traffic curve. The exact parameters of the traffic curves and the
tipping point can be generated using simulation based analysis of
the road network topology for different arrival patterns.