By Dimitris Triantafyllos and Carles Illera
Did you know that in Aimsun 8.2 you can now make use of a Turning Penalty Function (TPF) that perceives the costs from a control plan selected in the macro scenario? Did you ever use Junction Delay Functions (JDF) to model stop/yield signs during a static assignment?
Below you will find examples of TPF and JDF functions that can be used at:
Aimsun 8.2 introduces the capability of the TPF to access the control plan information (green time and cycle duration) of a turn and to include this cost in the link cost calculation. You’ll find one example in the template named ‘TPF – Example for Signalized Intersection’. This cost function calculates, as a function of the Assigned Volume, the average delay of each signalized turn based on the statistical calculation found in the 2010 Highway Capacity Manual (HCM).
Figure 1. Turn green time and cycle time at signalized intersection
Figure 3. Definition of the TPF – Example for Signalized Intersection
Figure 4. Cost of a turn post to a macro assignment
The Assigned Volume at this turn came out 339.62 PCUs, and the corresponding cost 0.20 minutes.
– Double-click on the TPF object to check the Python code. To plot a graph that shows how the cost value varies with the assigned volume of the turn, select one Static Assignment Experiment, one Vehicle Type and then just click on the desired turn.
Figure 5. A graph that shows how the cost varies with the assigned volume for a specific turn inside the Python-coded TPF
– If a Master Control Plan with various Control Plans is selected, then the average green time and cycle time will be calculated by taking into account the different plans, each weighted with its relative duration within the period covered in the scenario.
– If an Actuated Control Plan is assigned, then the TPF has access to the cycle (considered as fixed) and to the minimun and maximum green time defined for each phase in the control plan. You are responsible for implementing in the TPF a function that calculates the green duration to take into account in the computation of the delay.
When a yield or stop sign is associated to a turn movement, then another type of cost function, called Junction Delay Function (JDF), can be assigned to this turn to model the travel time or the cost as a function of conflicting turn volumes, the own turn volume or the origin section’s volume.
Figure 6. JDF – Example for Unsignalized Intersection
This JDF calculates the turn capacity depending on the conflicting turn volumes. Once the capacity has been determined, the JDF function evaluates the turn’s cost based on its Assigned Volume.
Figure 7. JDF – Example for Unsignalized Intersection can be defined in the turn object
Figure 8. Using the Table View to perform multiple changes at the same object type
Figure 9. Cost of turns post to a macro assignment
This JDF “Example for Unsignalized Intersection” is an example and can only be used for turns with a dedicated lane.
If a turn at a signalised intersection has conflicts with other movements during the green phase (e.g. permitted left turn), create a new JDF that captures the effects of both the signal timing and the conflicting volume.