Measuring and Analyzing Vehicle Position and Speed Data at Work Zones Using Global Positioning System

In order to analyze traffic characteristics at highway work zones, traffic flow has been measured through various types of traffic measuring devices. The limitations of the conventional traffic counters include: 1) it is not always easy to install and retrieve traffic measuring devices on highways because traffic conditions would pose a risk to traffic engineers; 2) they can only record traffic measurements at the places where the counters are installed. To overcome these shortcomings of the conventional traffic counters, a Global Positioning System (GPS) device was used in this study to measure traffic characteristics at Indiana freeway work zones. This paper demonstrates that GPS is an efficient tool in recording vehicle position and speed values and it can provide accurate and detailed information on traffic characteristics at work zones. The dynamic feature of the GPS collected data enables the traffic engineers to obtain the precise profile of vehicle speed as well as the geometric layout of roadway sections and work zones. With the GPS data, the average travel speed on a given roadway section or work zone can be calculated. It is also presented that the vehicle deceleration and acceleration rates, which could only be roughly estimated in an earlier study, can be readily calculated with high accuracy using the GPS data. Moreover, traffic delays and exact queue lengths at work zones can also be obtained through the GPS collected traffic data.