Bus bunching

Pulkbildung called the emergence of a coherent series of vehicles during traffic flow.

Pulkbildung by traffic signals

Pulkbildung the public transport

Pulkbildung (also: vernier effect ) is a phenomenon that occurs in local public transport. Indirect influence of trains running on the same distance trains, subways, buses, etc. tend variations in headway to strengthen further and further (positive feedback ): That is, vehicles after prolonged headway (or already late ) are lateness vulnerable, according to shorter headways (or already premature ), however verfrühungsanfälliger.

Where such disturbances lead to highly variable car-following time, this results in a non-uniform loading of the vehicles used by passengers with the result of differing passenger boarding and alighting times. The result may be the emergence of a bomber formations.

The description as vernier effect occurs because of the analogy with the vernier in measuring technology, which uses a similar effect to increase the accuracy of measuring instruments for the measurement of lengths and angles. To match this, it may, for example, when a railway line, take the common traits and their clock schedules are different ( for example, every 15 minutes, on line 1, every 20 minutes, on line 2), after some time cause interference. The schedule gets mixed up there.

Example

Line 1 with a cycle time of 15 min → vehicle comes to the minute 0/15/30/45 Line 2 with a cycle time of 20 min → vehicle comes to the minute 7/27/47

Thereof, shall be headways → result 7/8/12/3/15/2/13

Operational control systems ITCS can reduce this effect by the drivers existing schedule deviations are notified so that they can have an influence on the time intervals.