Meanwhile (traffic engineering)
In the traffic engineering is understood to mean (also protection time ), the time to through traffic signals signaled junctions between the end of the green time ( release time ) one-clearing traffic flow pass and the start of the green time of oncoming traffic flow needs. Maintaining the intermediate time ensures that the clearing traffic does not come into conflict with the incoming traffic (so-called collision case).
The length of the interim period varies depending on the number of traffic flows and the length of the clearance and entry routes. In Germany, the calculation according to the guidelines for traffic light systems (RiLSA) is prescribed.
At smaller junctions, the intermediate times between the vehicle traffic flows are usually around six to seven seconds. At particularly large intersections, the protection times between evacuating pedestrian traffic flows and intersecting vehicle traffic flows can be more than 20 seconds.
Calculation of the intermediate time
With
| term | definition | Note |
|---|---|---|
| Clearing path s r | Distance traveled between the stop line of the signal whose green phase ends and the conflict point. | In Räumweg the vehicle length l is Fz taken into account. For the sake of simplicity, flat lengths are used, for example six meters for motor vehicles. |
| Basic clearance s 0 | Distance between the stop line and the conflict point, measured in the middle of the lane | In Grundräumweg the vehicle length l Fz not considered. |
| Entry path s e | Distance traveled between the stop line of the signal whose green phase begins and the conflict point. | |
| Running-in time t e | Time for covering the entry path. | |
| Clearing speed v r | assumed minimum speed at which a vehicle drives over the intersection. | For motor vehicles traveling in a straight line, 10 m / s are usually assumed, for bicycles 4 m / s, and for pedestrians, a clearing speed of 1.2 m / s is generally assumed. |
| Entry speed v e | assumed maximum speed with which a vehicle drives onto the intersection immediately after the start of the green. | Normally 11.1 m / s is used for motor vehicles and 5 m / s for cyclists. |
| Overrun time t ü | Time from the end of the green, within which it must be expected that vehicles will enter the intersection. | In the first few seconds after the signal changes from green to yellow, vehicles that are just in front of the intersection can usually no longer be brought to a stop. This fact is taken into account by the overrun time . The crossing time for motor vehicles is usually three seconds, for bicycles one second. |
| Conflict point | Intersection of the driving line of the vehicle leaving the junction with the driving line of the vehicle entering the junction. | The route that the vehicles regularly use to pass the intersection is always decisive as the driving line . If different routes are regularly used due to the unclear junction design, the route that leads to the highest calculated intermediate time must be used as a starting point. |
| Conflict area | Area of the roadway that is used by both the evacuating vehicle and the vehicle entering. | For the sake of simplicity, clearance and entry routes are usually determined up to the point of conflict, thus disregarding the vehicle width. In cases in which the paths traveled intersect at an acute angle, this simplified procedure is not sufficient, the conflict area must be taken into account. |
A junction access point is rarely used by just one type of transport. Pedestrians and cyclists or cyclists and motor vehicles often share a jointly signaled entrance. In such cases, the intermediate times of the various traffic type combinations have to be calculated individually. The highest calculated value is used as the result, for example the result of the combination of the (relatively slow) clearing cyclists and the (relatively fast) entering motor vehicles.
Most control systems for traffic light systems work every second. Therefore, the intermediate times are usually rounded up to whole seconds. For security reasons, it is always rounded up.
In the case of short clearing paths and long entry paths, negative intermediate times can theoretically also result. However, the mandatory technical monitoring of the green interlocking prevents incompatible traffic flows from getting “green” at the same time. Therefore, this performance advantage cannot be used.