Analysis and evaluation of traffic flow at variable speed limit using the cell transmission model

Variable speed limit(VSL) is one of the highway ITS techniques designed to prevent accidents and traffic slow down by reducing congestion or speed variation between vehicles and lanes prior to arrive at the accident location by limiting speed. This is currently applied and operated on the autobahn in Germany, on M26 in the UK, and in other countries in Europe. In Korea, while people have recognized the need for variable speed limit beginning with Seoul's urban expressway and installed facilities in order to provide guide for speed limit per lane and lane use, there has not been enough development of algorithm for internal administration as well as research on the basic principles behind administering variable speed limit. This study is for modeling the VSL based on the traffic flow theory and the Demand-Supply method of the Cell Transmission Model(CT Model). CT Model is able to demonstrate the traffic features and shockwaves caused by VSL. And we verified the explanation of CT Model for the numerical example.