Estimating the Effect of Operational Improvements in the Houston Area

Measuring the effects of transportation system improvements has long been a challenge. Two estimates—the congestion index method and the travel delay method—are used to produce a range of possible benefits resulting from the implementation of transportation projects and programs. The congestion index method uses the roadway congestion index (RCI), and its relationship with congestion cost per capita, to estimate the benefit derived from operational improvements. The RCI provides an areawide assessment of congestion based on freeway and principal arterial street system daily vehicle kilometers of travel per lane kilometer data. The travel delay method calculates congestion cost by associating the value of time, cost of fuel, and cost of operating commercial vehicles with travel delay estimates. These two methods are used to estimate the effects of three types of transportation system improvement projects/programs—freeway traffic management system, high-occupancy vehicle lanes, and regional computerized traffic signal system— implemented on the freeway and principal arterial street system in Houston, Texas. Although only three operational projects/programs are discussed, it is possible to effectively evaluate the implementation of many other improvements using this methodology.