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Optimizing Detector Placement for High Speed Isolated Signalized Intersections Using Vehicular Delay as the Criterion
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1994-10-01
[PDF-3.03 MB]
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Edition:Interim: September 1993 - August 1994
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Abstract:On high-speed approaches to an isolated intersection, providing for dilemma zone protection may result in sluggish operation and this, in turn, may result in higher delays. A trade-off analysis of detector placement is, therefore, essential for optimization of dilemma zone protection and reducing delays. TEXAS Model (Version 3.2) was employed to determine optimal detector placement strategies on high-speed isolated intersections. Traffic volumes varied between 200 vehicles per hour (vph) per approach to 800 vph per approach. Mean speeds of 90 km/h (55 mph), 70 km/h (45 mph), and 55 km/h (35 mph) were simulated. Detector placements were developed for mean as well as for 85th percentile speeds. At approach volumes less than 500 vph per approach (250 vphpl), three detector layouts with the first or innermost detector located between 0 m (0 ft) to 18 m (60 ft) from the stop line, resulted in lower delays. However, at traffic volumes greater than 500 vph per approach (250 vphpl), three detector layouts, with the first detector between 24 m (80 ft) and 36 m (120 ft) from the stop line, resulted in lower delay. This trend exists for detector layouts for both mean and 85th percentile speed. Statistical analysis shows that no significant difference in delays for detector layouts with the first detector between 0 m (0 ft) and 18 m (60 ft) within that group. Detector layouts with the first detector placed between 24 m (80 ft) and 36 m (120 ft) from the stop line had no significant difference in delays within this group. Regression analysis performed on delay and cycle length for different detector layouts showed a strong linear relationship between them. At low approach volumes, there was no effect of both mean and 85th percentile speeds on delay, whereas at higher approach volumes, 85th percentile speeds resulted in higher delay.
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