Ramp metering (RM) is to deploy traffic signals on the ramp to dynamically control the ramp vehicles into the mainline of the expressway, which can smooth the mainline traffic flow and utilize the existing expressway capacity effectively. According to the control range, RM can be divided into local RM and multi-ramp RM. Local RM can solve the local congestion problem to a certain extent, but it does not consider the regional or system problems, which may cause congestion shifting and lead to congestion on other roads in the region. ALINEA algorithm is a typical local RM algorithm, but ALINEA algorithm has no prediction mechanism and thus cannot handle the sudden change of traffic flow smoothly. Besides, few studies to develop multi-ramp RM algorithms based on congestion risk prediction. Therefore, this study improved the ALINEA algorithm and established a system-optimal dynamic RM algorithm based on real-time congestion risk prediction.
 

Ramp metering;ALINEA algorithm;multi-ramp RM algorithms;congestion risk prediction