Good afternoon everybody,

I was wondering if we can code turbo lane in synchro in a T intersection. we have this T intersection:

NB direction carries 3 through lanes and a left turn bay.

SB direction carries 3 through lanes.

EB direction carries one left turn lane and a right turn lane.

Now, our client wants to code a turbo lane at this intersection, which will allow two out of three through lanes in the northbound direction go all the time. these two lanes will have no effect with the signal at this intersection and get green all the time while the left turn bay and left most through lane get red signal when eastbound left turn gets green signal. Can we code this kind of movement in synchro?

One option i was thinking is to code two through lanes separately. I would really appreciate your input. Thanks.

sharad

I have no experience with this sort of intersection, but here are a couple of thoughts:

1. Code a typical T-intersection, but with just one northbound thru lane. Assume a volume of vehicles that would choose to stop in this lane instead of going through the turbo lanes. You could even re-calculate the LOS report by hand using the same NB delay time, but using the true NB volume to drop the delay. (Is that how you calc delay for turbos?)

2. Place dummy nodes north, south, and east of the intersection to create a two-lane bypass. The north and south dummy nodes would be unsignalized/free-flow. You would have to go into the simulations settings to change the lane alignments to R-NA or L-NA on the approaches to prevent turbulance at the dummy nodes. It would help to turn on intersection paths under Options-Map Settings.

Like I said, I've never done this before. It's just my two cents worth.

This message has been edited. Last edited by: Mark,

Thank you very much Mark. I really liked your ideas. I will probably try number two. However, i will be waiting for some more information regarding coding of turbo lanes.

This sounds a lot like a place near where I grew up, US 1 in Melbourne, FL.
6 lane highway, with 2 northbound lanes that get all-green signals.

You can imitate this in a network, but you'll wind up making a bypass link - it departs the NB lanes before the signal and then re-merges after the signal. As a separate link, you have assign it volume, and it won't be coded as a NBT but as a NBR turn lane (adjust turn speed in simulation settings). Make it a very slightly curved link, and adjust your lane offsets to make it look good, and it should work.

You'll need data from the site about how much volume uses the all-green lanes vs. the one lane that is stopped by the signal. If this is a new site, you probably need to find a comparable site and get some data for similiar times.

Eric
Caltrans