Estimating Delay Time at Signalized Intersections by Probe Vehicles

Delay times at intersections are one of the most important types of information for ATIS (advanced traveler information systems). Even though probe vehicles have already been used to directly measure delay times, the ongoing collection of real-time delay information on a large scale depends on reducing transmission costs to a reasonable level. Reducing the GPS transmission frequency is one effective means of lowering costs. This paper attempts to assess the sensitivity of delay measurements to differing data transmission intervals. Two delay measurement algorithms are developed corresponding to high-frequency probe data (at 5 second intervals in this paper) and lower-frequency data (from 10 to 60 seconds). Results show that delay detection and measurement sensitivity decrease rapidly with increasing transmission interval. Delays measured from data transmitted at 10-second intervals match the 5-second values in about 74 % of cases. The relative accuracy drops to 37 % for data transmitted at 60-second intervals