Error description:
The reason for blockages caused by lags can be found in the extension flag parameter. Such a blockage could be reproduced in VISSIM at an example intersection.
As can be seen from the above recording, traffic stream 10 (VS_B) has the status 20 (Zust) at second 917 (Sekunde). This means that it has a red command that has not yet been executed. This also means that an lag is active.
In the next second, the state of the traffic stream was reset from 20 to 15 (the traffic stream has no traffic, but can extend further if necessary depending on the extension flag). However, the green command was not withdrawn from the conflicting traffic streams.
The reason for this lies in the extension flag:
In the example above, traffic stream 10 is green as a minor stream without call. After the minimum green time 1 has expired, the extension flag Vgmin1 (as minor stream without call he can only extend to minimum green 1) is checked and the traffic stream is no longer allowed to extend. However, this overlooks the fact that the traffic stream already has a red command and it is set to the wrong state 15.
Error avoidance:
To avoid this error, the extension identifiers Vgmin1, Vgmin2, Vgmax1 and Vgmax2 must therefore not be used in vs | plus parameterisations prior to version 8.1 for traffic streams that are used in lead or lag.
Version dependency:
The error can occur from vs | plus version 8.0.
In vs | plus version 8.1, this error behaviour has been fixed and the above-mentioned extension identifiers can be used again.