faq 110974343

What is the logic of vehicle enters traffic whenever the capacity is full?

by Enoch Lee on 2017-07-31 14:59:21

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Currently I am simulating a congested network. The simulation result shown there was spill back jam to a link.

The extract of network was like this.

congested network==>C==>A==>B==>congested network

In the meantime, there are plenty of transit lines that start at a stop facility at link A. However, I found that in the congested hour for link B, the transit drivers delay departures (The vehicle did not enter traffic) until the link B congestion gone. On the other hand, the car drivers also delayed enter traffic (For example, some agents started their trip at 8:30, but their cars enter traffic at 12:58). The behavior that a lot of drivers start the trip in link B made it worse.

I am wondering what is the logic behind the hidden queue, and is there any way for me to prioritize the transit vehicle to enter the traffic (in order to encourage agents to take the bus)?

Thanks for your help in advance.

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Comments: 1

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Re: What is the logic of vehicle enters traffic whenever the capacity is full?

by Marcel Rieser on 2017-08-25 07:48:48

By default, vehicles already on the road are preferred over vehicles trying to enter traffic. This is why the transit vehicles departing on a congested link have to wait until the link is no longer congested.

The qsim provides a configuration option to modify this:

<module name="qsim" >
   <!-- decides if waiting vehicles enter the network after or before the already driving vehicles were moved. Default: false -->
   <param name="insertingWaitingVehiclesBeforeDrivingVehicles" value="false" />
   ....
 </module>

Set qsim.insertingWaitingVehiclesBeforeDrivingVehicles to true to have departing vehicles having a higher preference than vehicles on the road. This setting affects all vehicles, not only transit vehicles. Be aware that with this setting being true, a potentially much larger number of vehicles will be on the network, resulting to even heavier congestion than what you observed so far.