Lane Choice Rules in Paramics

UPDATED: April 26, 2017

The limitation of a vehicle being only able to see one signpost effectively means that two exits to a freeway at very close intervals will mean that vehicles unaffected by the first exit will continue in any lane before seeing the second signpost, which may then lead to the vehicle having to cross several lanes in a short space in order to exit from the second exit.

Lane Choices Rules define the percentage split across lanes dependent on immediate path of the vehicles overriding other signpost and behavioural aspects. In this regard Lane Choice Rules should only be used when in specialist situations where Signposting and other behavioural mechanisms are not effective.

It is highly recommended that Lane Choice Rules be added with careful consideration and checked thoroughly when edits are made to the network.

Lane Choices are defined by the user using lane use percentages, but are converted into lane ranges by the software to prevent excessive weaving.  This can sometimes cause the Lane Choice Rule to not behave as expected. If the user assigns a lane choice to use 50% lane 1 and 50% lane 2, the software interprets this as 100% lane range 1-2. To translate the lane %s in to Lane ranges take the lowest percentage this will be spread across all of the lanes and multiplied by the number of lanes. Subtract this amount from each percentage and repeat. So with 60/20/20 - 20 is the lowest percentage x 3 lanes = 60% for lanes 1-3, Lanes 2 & 3 both now have 0% remaining and lane 1 has 40%, so 40% have a range of 1-1.  Concave values will cause errors so no 40/20/40. Looking at a 4 lane section then we might have 25/35/25/15, so we have 60% for 1-4, 30% for 1-3, 10% for lane 2-2.    

To see a video on this subject please click here and select the session entitled "Adding Lane Choices".


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