Measuring road congestion

The methodology presented here allows to measure and monitor road congestion across Europe using data from TomTom invehicle navigation systems. The approach is based on the analysis of a large number of real vehicle speeds that have been measured on each road link and the application of algorithms that allow the estimation of congestion indicators for specific types of roads during selected time periods. The results include the detailed mapping of recurrent congestion both geographically and temporally, as well as the comparison of the quality of service of road networks between different zones. The data used represent real speed measurements from in-vehicle navigation systems for different time periods and days of the week. The large number of "probes" (over 1 trillion of measurements) gives a highly accurate and representative picture of the actual driving conditions across the European road network. The data collected are clustered in groups of speed profiles which represent change in average speed behaviour along a road link in five-minute time intervals over a 24-hour period. specific speed profile assigned per day of the week. The average speed on a specific link during a certain time period can be compared to the benchmark speed estimated for the link under free flow conditions or against selected threshold values. As a result, indicators of congestion for different time periods can be measured and compared across links, regions and countries.