For various reasons, the Transport Research Centre in The Netherlands decided to validate and assess for the second time part of the SCOOT urban traffic control system in Nijmegen. This paper describes the second validation and assessment, presents some of its results, and draws some conclusions. The validation's first task was to revalidate some links which had not been properly validated, using on-street measurements. The second task was to investigate whether to use the SCOOT mechanism for automatic measurement of saturation occupancy, under what conditions. The final task was to reconsider the SCOOT gating mechanism on the Waal Bridge. Several other adjustments were also made. The purpose of the assessment was to measure the effects of the improved SCOOT system; there were several differences of methodology between the two assessments. Travel times, queues, traffic flows, and estimated delays were measured, and the data were screened for such aspects as weather conditions, incidents, and control system malfunctions. Results are presented for delays, demand, travel times, and the queue lengths on the Waal Bridge. Although the results of the second assessment were better than those of the first, the Nijmegen local authority decided to switch off the SCOOT system for several reasons.
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