This article studies the usefulness of parallel processing in real-time traffic-flow simulation based on continuum modeling of traffic dynamics. Computational fluid dynamics (CFD's) methods for solving simple macroscopic traffic-flow continuum models have been studied and efficiently implemented in traffic simulation codes (on serial computers) in the past. We designed a traffic-flow simulation code and mapped it onto a parallel computer architecture. This traffic simulation system is capable of simulating freeway traffic flow in real time. Tests with real traffic data collected from the freeway network in the metropolitan area of Minneapolis, MN, were used to validate the accuracy and computational rate of the parallel simulation system. The execution time for a 2-h traffic-flow simulation of about 200 619 vehicles in an 18-mi freeway, which takes 2.35 min of computer time (on a single-processor computer simulator), took only 5.25 s on the parallel traffic simulation system. This parallel system has a lot of potential for real-time traffic engineering applications.

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This paper implements and analyzes a highway traffic-flow simulation based on continuum modeling of traffic dynamics. A traffic-flow simulation was developed and mapped onto a parallel computer architecture. Two algorithms (the one-step and two-step algorithms) to solve the simulation equations were developed and implemented. Tests with real traffic data collected from the freeway network in the metropolitan area of Minneapolis, MN, were used to validate the accuracy and computation rate of the parallel simulation system (with 256 processors). The execution time for a 24-h traffic-flow simulation over a 15.5-mi freeway, which takes 65.7 min on a typical single-processor computer, took only 88.51 s on the nCUBE2 and only 2.39 s on the CRAY T3E. The two-step algorithm, whose goal is to trade off extra computation for fewer interprocessor communications, was shown to save significantly on the communication time on both parallel computers.

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