Optimal Placement of Point Detectors on Virginia's Freeways: Case Studies of Northern Virginia and Richmond

摘要

In Virginia, point detectors in the Northern Virginia and Hampton Roads regions are placed at approximately one half mile spacing. This density is a product of early requirements for incident detection that have proven ineffective and perhaps unnecessary. There are other important uses of the data that likely have different requirements for detector placement than the original incident detection focus. For example, there is a desire to derive travel time estimates from the point detector data for the purpose of performance monitoring. To do this, the detectors are to be placed so as to effectively sample the conditions on a freeway. Unfortunately, little guidance exists on how to place detectors for effective sampling. The purpose of this research project was to develop a decision support methodology to identify the optimal locations of a finite set of point detectors on a freeway corridor in order to minimize the error in travel time estimation, within the constraints of available capital and maintenance funding. Case studies of freeway sections in three regions were conducted to demonstrate the utility of the newly developed tool. While there are potentially other important uses of the data collected by freeway point detectors, the recommendations in this report deal specifically with the issue of travel time estimation.