00647273

Component

Signal timing optimization involves the selection of four basic design elements: phase sequence, cycle length, green split, and offset. None of the available signal timing models is considered adequate to optimize all four design elements, particularly in two-dimensional networks. Among the current models, TRANSYT-7F is most effective for timing, but it does not optimize phasing. Researchers have considered several methods for enhancing TRANSYT-7F to include phasing optimization but thus far no method has proven practical. An exhaustive search of possible phasing combinations is computationally prohibitive; thus a new approach is needed. Genetic algorithms (GAs) are heuristic probabilistic search procedures that have been applied to a wide range of engineering problems. The use is investigated of a GA in combination with the TRANSYT-7F optimization routine to select all signal timing design elements. The main purpose of the GA in the proposed scheme is to optimize phase sequences. Two implementations of the GA model are presented. In the first, the GA and TRANSYT-7F optimization routines are executed concurrently to achieve an optimal solution. In the second, the GA is allowed to optimize cycle length, phase sequences, and offsets. Then TRANSTY-7F is used to adjust the resultant signal timing. The results suggest that both implementations have potential for optimizing signal phasing and timing. However, the first method produces more consistent results. It also requires longer execution time.

This paper appears in Transportation Research Record No. 1421, Traffic Control Devices, Visibility, and Traffic Signal Systems.

English

p. 104-112

1993

Transportation Research Record

0309055741

Figures (4) ; References (18) ; Tables (2)

Exclusive phasing; Genetic algorithms; Heuristic methods; Offsets (Traffic signal timing); Optimization; Sequencing; Traffic signal timing

TRANSYT (Computer program)

Highways; Operations and Traffic Management; I73: Traffic Control

TRIS, TRB

Jun 2 1994 12:00AM

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