ABSTRACT

This paper describes a scalable approach to simulation of decentralized adaptive signal control

systems, motivated by our interest to provide a basis for assessing the benefit of the Surtrac

adaptive signal control system at a potential deployment site in advance of installation. The

approach centers around a simulation controller interface called VISCO, which links the VISSIM

microscopic traffic simulator to a set of externally hosted local intersection control processes.

Local control processes are free to communicate with each other and exchange control

information in the same manner that they would in a field implementation. VISCO coordinates

all interaction with the simulator process to create a distributed software-in-the-loop simulation

architecture. To illustrate and analyze the efficacy of the approach, we summarize a simulation

analysis that was conducted of the downtown triangle area of Pittsburgh PA. A 63-intersection

VISSIM model of this site is described and analyses are presented to characterize both the

efficiency of the distributed architecture and the potential utility of Surtrac adaptive control.

With respect to the former, the distributed simulation of local Surtrac control processes is found

to run in roughly 4.4 times faster than real-time, in comparison to the 14.4 times faster than real

time speed that a conventional VISSIM simulation of this model with fixed timing plans

performed. Experiments also show that the VISCO distributed architecture is effective in

significantly reducing the cost associated with VISSIM’s external COM interface. With respect

expected improvement of adaptive signal control in the downtown triangle area of Pittsburgh, the

simulation analysis shows strong benefit of Surtrac over both the existing timing plans in use in

this area and Synchro optimized plans that were generated with perfect knowledge of traffic

volumes and turning counts.