Study on the Speed Criteria of Expressway Traffic Conditions for FTMS Using Break Points of Three-Regime Traffic Flow Models

There have been strong requests for the increase of the posted speed limit on expressways in Korea, due to the recent improvements in vehicular performance and expressway facilities. Therefore, the speed limit of Kyungbu expressway between Seoul and Cheonan was increased from 100 km/h to 110 km/h, in 2010. At the same time, the speed criteria for identifying expressway traffic conditions, including congested condition, transition condition, and uncongested condition, were changed from 30 km/h and 70 km/h to 40 km/h and 80 km/h. This research was initiated to verify the feasibility of the change in the speed criteria for identifying expressway traffic conditions through the analysis of break points of three-regime traffic flow models using defected data collected before and after the speed limit change. Conclusively, the change of the speed criteria for identifying expressway traffic condition was found out to be appropriate to represent traffic conditions of the expressway segment.