Ramp meter
A flow control system regulates in increased traffic congestion the flow of vehicles on congestion- risk road sections.
Application to highways
A ramp metering system (in short: ZRA ) on highways regulates in more traffic inflow retracts vehicles on motorways or motorway-type roads with a traffic light system (in short: LSA) in the access ramp. It achieves its positive effect by long vehicle groups, which often occur at traffic signals in the downstream network can be divided into individual vehicles or platoons with few vehicles. This will avoid that in no time pushing many vehicles virtually simultaneously on the main road and need a suitable gap. The ZRA on the access ramp to the highway is depending on traffic in all cases realized in Germany. That is, the round-trip time as a function of the ZRA measured on the main road and the entrance ramp traffic characteristic values is calculated. It is important to find the best compromise between the two traffic flows the main carriageway and the access ramp. In any case, the formation of a Return critical congestion in the downstream road network is attempted to be prevented. There are now with the plants in North Rhine -Westphalia before many years of experience, which confirm that ZRA positive impact on congestion events and the accident. In total there are at motorway slip roads in this state alone 75 ramp metering systems in operation. Since 2012 engaged in Baden-Württemberg 3 ZRA. The increased volume of the colliding vehicles is due in Germany predominantly of previous traffic lights that accumulates the colliding vehicles and a lack of connection points.
This method was adopted from the United States and there already being used in the 1990s to limit the capacity of double ramps. The right lane of the highway is best measured on vehicle frequency and regulates the Zufahrfrequenz or shut down. The facilities there are only installed to keep the highway and feeder liquid. To enable the Green Wave on the feeder, was built in each direction per second ramp. It is omitted in the mouths of the feeder to second Linksabbiegerphase and the feeder gets longer green phases. In practice, this mainly not completely stopped, but a leisurely flow of traffic on the ramp metering system generates. Carpools are mostly excluded from the scheme and may enter unlimited. The ramp metering system is there called ramp meters.
Application on city streets ( the "gatekeeper traffic light " )
Ramp metering systems are not to be confused with so-called gatekeeper traffic lights in the city's main road network. These special lights is attempted by setting a maximum flow to relieve a bottleneck section. This is usually accompanied with congestion before the porter lights. The goal here is not to let the traffic volume in the bottleneck rise above its capacity as a jam at this point would be even more detrimental than before the traffic light porter. So in the sense of an intelligent traffic control, it is often helpful to let in just enough vehicles in the bottleneck that it can function without traffic jams at peak performance. While it may then come to the doorman traffic lights to return congestion, overall, the road network with such a control, but more powerful and the average waiting time for all road users is lower.
In addition, access metering can be used to hold, for example, common banking- used by tram and car traffic road sections. Also can be shifted (eg commercial areas) congestion effects from sensitive areas (eg residential areas ) to less sensitive areas to reduce noise and pollution of local residents. Such ramp metering systems can help to avoid costly or umfeldunverträgliche road extensions.
Porter traffic lights are also used to focus in particular with regard to the noise emission motor vehicle traffic in residential areas in time. Your need is mainly owed by the lack of connection points poor transport links.