Two-way left turn lanes

[TEEI]

I have to do a capacity on a two-lane undivided roadway with a suicide(two-way left turn lane) lane in the middle. Do we have to account for this lane in the capacity analysis or do we have to just consider the roadway segment as a two-lane undivided? Please throw some light on this.........

Thanks
TEEI

 

[ACtrafficengr]

First, two-way left turn lanes aren't true "suicide lanes." Suicide lanes were center lanes used for passing in either direction. AS you might expect, they worked okay in rural areas during the early days, but as volumes increased, so did head-on crashes.

The effect of a TWLTL on capacity depends on marginal devleopment. If you have a lot of mid-block left turns, then capacity will likely be higher with the TWLTL than without. If not, capacity will be similar to a two lane road with passing prohibited. It really depends on whther getting left turners out of traffic will offset prohibiting passing.

I'm not sure the HCM has a way to account for TWLTL's or not. If any grad students are reading this, it may be a problem worth investigating...

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