Optimization for Oversaturated Conditions
The following steps may be applied to select the best control strategy for an oversaturated
traffic system.
First, the critical link(s) and the type of oversaturated conditions exist in the system need to
be identified. A critical link is defined as the most downstream link on a continuous,
upstream-downstream list of oversaturated links. The level of congestion in the system as
well as the critical links can be determined by performing a TRANSYT-7F optimization
run based on minimizing the DI (e.g., excess fuel consumption) with the step-wise
simulation. If the system is still found to be congested with the optimal timing, the stepwise
simulation with optimization of the DI plus queuing penalty on the links with queue
problems should be applied.
Second, if the above process is unable to eliminate the congestion problem, the new
objective functions with or without the queuing penalty can be tried. The critical links for
which the throughput (or the queuing ratio) is to be optimized should be specified for
optimization.
In short, TRANSYT-7F is now a more complete signal timing and traffic analysis tool. It
now more realistically examines saturated conditions in addition to its historical modeling
of undersaturated conditions.