I've noticed several times that in SimTraffic, in a heavily congested network, vehicles routinely get stuck trying to merge into congested lanes and backlog the entire upstream network, resulting in a complete stoppage in traffic (even once the downstream traffic is moving again).

Is there a way to detect/avoid this?
It makes for frustrating simulation runs when it runs for an hour and gives large innaccurate delay numbers because vehicles didn't move for a full 15 minutes.

Thanks!
D

Hi D,

First, let me have you check your build version. You can see this with the command Help->About. For version 6, this should be build 609. If not, you can get this from www.trafficware.com/download.htm.
Next, you might need to modify the Lane Change Distances (in version 6 only). On the link that is giving the problems, double click on the link. You will see a button that indicates Lane Change Dist, [Edit]. Click this for the direction of interset. You might need to increase these values to get vehicles to make lane changes further away. This will help so they don't go too far down the link before making this change and getting "stuck".

If this doesn't help, please do feel free to send us the file (the Synchro file) for investigation.

Thanks,

John.

Thanks! Downloaded the latest build and it seems to work now!

cheers!

John,
I am experiencing the same problem with regularity. I have adjusted the lane changing distances on the downstream link to several distances, however, I need to keep the lane changing distance quite short to make sure I get equal use of my dual left turn lane that is also at the upstream intersection. My vehicles get stuck on right turn channelized lanes (both dual and single ones). I have only noticed it at RT channelizations however. Is there a certain distance (formula?) that vehicles must have prior to the downstream link to ensure this problem does not occur?

...and yes, I have the latest build...

Hi Paul,

If the issue is related to the channelized right, you'll actually get a warning message that appears when you launch SimTraffic. In cases like this (where the downstream intersection is quite close) you may need to reduce the radius of the right turn. At worst, you may need to remove the channelized right turn to get this to simulate. Unfortunatly, the algorithms used in these types of models can't fully model the "unique" behavior that some drivers do.

Another note. You also won't want to make the Lane Change Distances too small. It will be case dependent, but normally values of less then 20 will cause problems and vehicles can get stuck.

Thanks,

John.

I don't actually get a warning message and it happens when I don't change the lane changing distances either. The link distance in this case was about 100 metres away downstream. I did try various curb radii as well...it seemed to work sometimes and get stuck others.

I'm having the same issue with double left turns merging to a signle lane on the far side of the intersection. The lookback distance *must* be short to ensure equal usage of the lanes. But I also get this problem with longer lookback distances such as 100 feet, or 175 feet. (I also have the most current build)