Turns show basically the same correlation between capacity and travel time as links. The only difference results from the fact that a turn does not have a length and that the travel time t0 therefore comes from the turn time penalty.
The turn time tCur in the loaded network then results from the selected VD function and the relationship between the current traffic volume q and the capacity qmax:
- Input: Free flow turn time t0 (turn time penalty) [s]
- Input: Volume q of the turn [car units/analysis time interval]
- Input: Capacity qmax of the turn [car units/analysis time interval]
- Input: VD function, for example BPR function from U.S. Bureau of Public Roads
- Result: current turn time in the loaded network [1], for example
To model turn times which do not depend on capacity, a constant VD function must be chosen.
How the impedance at a turn depends on these parameters in particular, depends on the set method for impedances at nodes (Impedances at nodes).
