Bonus greens can be modelled by changing the “relative start displacement” or “relative end displacement” values in order to differentiate between ‘actual’ green time and ‘effective’ green time. Within the TRANSYT model, these values ‘combine’ with the network wide start and end displacement values – which are often set to 2 seconds and 3 seconds respectively. “Relative start displacement” and “relative end displacement” values can be either negative or positive, and are specified as part of the PHASE DATA.
Note: In situations where two traffic streams are controlled by the same phase, but require different displacement values, the phase should be copied, and set to control just the one traffic stream. The displacement values can then be changed as required on just that particular phase, leaving the other phase (whose actual green times will be the same as the other phase) with the original start/end displacement.
In TRANSYT 12 and earlier versions bonus greens were part of the Start Lag or End Lag. The Start Lag, which included the preceding interstage time, could be reduced in length to accommodate a bonus time at the start of green, and the End Lag could be lengthened to allow for an extended effective green time, say, to model traffic turning right in the intergreen having stored in front of the stop line.