A Case Study on Measuring Travel Time, Speed, and Delay Using GPS-Instrumented Test Vehicles

The Georgia Institute of Technology research team has recently conducted an arterial performance monitoring study on a 15-intersection signal control system in Cobb County, Georgia, using GPS-instrumented test vehicles. This paper describes the defined GPS error detecting criteria and the data reduction procedure developed by the research team. Error detecting criteria are developed based on distance between two consecutive GPS points, acceleration rate, deceleration rate, horizontal dilution of precision (HDOP), and number of satellites. The impact on percentage of GPS data eliminated as a result of these varying criteria is given and performance measures are calculated for several different criteria values, allowing for a determination of the sensitivity of the performance measures to the error checking criteria set.