Recent years have seen a growing interest in monitoring travel time variability (TTV) on the highway network and developing methods to forecast TTV. Work currently (February 2008) being undertaken for the UK Department for Transport to develop methods for calculating and forecasting TTV using data collected from Global Positioning System (GPS) tracker-equipped vehicles is described. Primary data on vehicle location and time can be transformed into data on times taken to traverse different links on the road network. A database has been constructed comprising travel times for individualvehicles on 34 routes (up to 12km long) within the 10 largest urban areasin England for a period of 3 years. This database on individual vehicles has been used to construct a TTV database containing data on the standard deviation of travel time along individual links in these routes as well asjourneys comprising more than one consecutive link. The quality of the database and its usefulness for monitoring TTV is described. The analysis undertaken to understand the impact on TTV of such factors as link/junction characteristics and journey length are considered. This will be followed by indications of appropriate relationships that can be used to predict TTVin urban areas. How changes in TTV can be incorporated into an assessmentframework, thereby providing a monetary estimate of the forecast benefitsdue to changes in TTV following a policy or scheme intervention, is demonstrated. For the covering abstract see ITRD E145999
Samenvatting