Ramp metering is one of the many dynamic Traffic Management Systems that have been applied to the Dutch freeways. Ramp meterings can decrease or prevent congestion. Untill 2005 about 50 ramp meterings are to be installed in the Netherlands. The question is: will they actually be installed? The negative effects that ramp meterings can have on urban traffic networks are the cause of great resistance from the urban road maintenance authority. Another effect of the implementation of (local) ramp metering can be the relocation of congestion. Local improvement can lead to worsening of the traffic flow in the total traffic network. The objective of this thesis is to gain a clear understanding of the effect of ramp metering in a traffic network (especially the urban traffic network) and to bring up attention points for the development of a ramp metering control which tunes the traffic flow of the freeway and the urban road. To reach this objective, several ramp metering controls will be considered by using the microscopic traffic flow model AIMSUN2. The effects on the freeway and the urban road will be analysed in an artificial traffic network, The different ramp metering controls are local ramp metering (Alinea), coordinated ramp metering (Metaline) and a new metering control. This new - relatively simple - control takes into account the traffic flow on the freeway and the traffic flow on the urban road. By doing so, a tool is developed for reaching consensus between the road maintenance authorities about the installation of ramp meterings. In this study no route choice has been taken into account. The (simulation)study proved that the activation of ramp meterings does not necessarily have to be based on the traffic state at the freeway. Also other circumstances can activate ramp meterings ; as a result of ramp metering blocking back to the urban roads can occur. Due to this undesirable consequences for the traffic on the urban road can arise ; when there are several ramp meterings in a traffic network tuning between these ramp meterings is desired ; a more intelligent ramp metering control can be used to decrease or prevent negative consequences on the urban road due to ramp metering. In comparison with no metering the traffic on the freeway will still have a (reasonable) reduction of the total delay time. The possible effect is removing the doubt of implementation of ramp metering. Future work should lead to the development of a perfectly working integral and continuous algoritm of this ramp metering control. This algoritm should consider the traffic state of the whole traffic network. In this study, points of attention for the development of this new ramp metering control are formulated: determine the area detection of the ramp metering ; imbedding the present buffer on the onramps and on the urban road ; adjustment of available traffic lights at the underlying junction ; determine a measure of disturbance on the urban road as a result of the metering ; distinguish between different traffic states in the traffic network (on the freeway and on the urban road) and determine the matching variables. (A)
Abstract