Flow control system

from Wikipedia, the free encyclopedia
Scheme of such a system on expressways
Flow control system L 1209 to the B 27 near Filderstadt .
Flow control facility on Miller Park Way to Interstate 94 in Milwaukee

A flow control system (ZRA for short) regulates the flow of vehicles to road sections at risk of congestion when the traffic volume increases . It is a traffic light that is installed on the ramps of expressways.

Use on expressways

A flow control system on expressways regulates the flow of vehicles entering on federal motorways or motorway-like roads by means of a traffic light system (short: LSA) in the access ramp when there is increased traffic . It achieves its positive effect by dividing long vehicle clusters, which often arise at traffic lights in the downstream network, into individual vehicles or clusters with a few vehicles. This prevents many vehicles from pushing onto the main lane practically at the same time and requiring a suitable gap. The ZRA on the access ramp of the motorway is traffic-dependent in all cases implemented in Germany. This means that the cycle time of the ZRA is calculated as a function of the traffic parameters measured on the main lane and the access ramp. The aim here is to find the optimal compromise between the two traffic flows on the main carriageway and the access ramp. In any case, an attempt is made to prevent the formation of a critical backlog in the downstream road network.

In the meantime, many years of experience have been gained with the systems in North Rhine-Westphalia , which confirm that ZRAs have a positive effect on congestion and accidents. A total of 75 flow control systems are in operation on the motorway access roads in this state alone. Baden-Württemberg has operated 3 ZRAs since 2012. The increased number of approaching vehicles in Germany is mainly due to preceding traffic light switching, which accumulates the approaching vehicles, as well as a lack of connection points.

This process was adopted from the USA and used there as early as the 1990s to limit the capacity of double ramps . For this purpose, the vehicle frequency is measured on the right-hand lane of the motorway and, based on this, the access frequency or shutdown of the system on the ramp is regulated. The systems are only installed there to keep the motorway and the feeder flowing. In practice, traffic is usually not stopped completely, but a leisurely flow of traffic is generated in front of the flow control system. Carpools are mostly exempt from the regulation and are allowed to enter without restriction . The flow control system is called the ramp meter there.

Use on city streets ("gate lights")

Flow control systems are not to be confused with so-called porter lights in the city's main road network. With these special traffic lights an attempt is made to relieve a bottleneck section by setting a maximum inflow. This is usually accompanied by traffic jams in front of the gate lights. The aim here is not to let the volume of traffic in the bottleneck exceed its capacity, as a traffic jam at this point would be even more disadvantageous than in front of the gatekeeper traffic light. In terms of intelligent traffic control, it is often helpful to only allow enough vehicles into the bottleneck that it can function with maximum performance without congestion. It is true that backlogs can then occur at the porter lights, but overall the road network is more efficient with such a control and the average waiting time for all road users is shorter.

In addition, porter circuits can be used to e.g. B. to keep road sections used jointly by trams and cars free of traffic jams. Traffic jams can also be relocated from sensitive areas (e.g. residential areas ) to less sensitive areas (e.g. commercial areas ) in order to reduce the noise and pollution of residents. Such flow control systems can help to avoid costly or environmentally incompatible road extensions.

Gate lights are also used to concentrate motor vehicle traffic in residential areas over time, particularly with a view to noise emissions. Their necessity is due to poor transport connections mainly due to the lack of connection points. On the heavily polluted Reuterstraße in Bonn (connection, inter alia, BAB 565 - B 9 - BAB 562 through the districts of Poppelsdorf , Kessenich and Südstadt ), the establishment of a gate light has been examined since the end of 2019 in order to reduce nitrogen emissions and thus another lawsuit by the German environmental aid to forestall. A decision about the need for a facility should be made in the next one to two years if a benefit can be confirmed by an expert and at the same time the requirements for NO x emissions are not met.

literature

  • Konrad Stöcker, Stefan Trupat: The influence of a flow control of junctions on the improvement of the traffic flow on motorways. (= Research Road Construction and Road Traffic Technology. Issue 802). Bonn 2001, OCLC 70950637 .
  • Roland Trapp: Development of a proactive procedure for ramp inflow control (inflow control) and the evaluation of its effect in comparison to other control methods. (= Aachener Mitteilungen Straßenwesen, Erdbau und Tunnelbau. Issue 49). Institute for Roads Aachen, 2006, ISBN 3-925163-38-7 .
  • Research Society for Roads and Transport ( FGSV ): Instructions for flow control systems (H ZRA). (= Research Society for Roads and Transportation. 318: W1). Cologne 2008, ISBN 978-3-939715-75-7 .

Individual evidence

  1. Ronald Reagan Freeway (US 118) 34 ° 16 ′ 55.6 ″  N , 118 ° 44 ′ 40.4 ″  W.
  2. ^ Rüdiger Franz: Reuterstraße in Bonn threatens the gate light. In: General-Anzeiger Bonn . January 23, 2020, accessed January 23, 2020 .

See also