A Simulation Study on City Expressway onRamp Metering

Abstract:

As a case study,three wellknown onramp metering algorithms,including fixedtime,Alinea and Flow,were evaluated via traffic simulation on Shenzhen Chunfeng expressway on various traffic demand levels,the parameters calibrations were also expatiated. Simulation results show that onramp metering can effectively improve mainline traffic when traffic demand is higher than a certain level.Both Alinea and Flow perform better than fixedtime metering,but increase ramp delay and queue obviously. Flow outperforms Alinea in this case study because the traffic bottleneck is closely related to its upstream onramps traffic.Finally,the scenarios of adding queue adjustment into Alinea and Flow were simulated.Results show that the distance of queue detectors to ramp entrance plays a key role to tradeoff between the mainline congestion and onramp queue.

Key words:onramp metering; simulation; fixedtime; Alinea algorithm; Flow algorithm