I'm not clear on the question? Are you referring to opposing double left turn lanes operating under protected permissive phasing, or just opposing protected permissive phasing?
The Highway Capacity Manual (page 10-22)recommends protected left turn phasing if more than a single lane is being provided. I can not recall ever seeing a permissive double left turn lane at a traffic signal.
In Rhode Island we have used opposing protected permissive left turn phasing, but only if a left turn lane is provided.
In the absence of left turn lanes a protected move can only be provided in one direction.
the intersection i am refering to has a east bound dual left turn that is a protected only turn. it is one ofthe inside lefts of a diamond interchange cofiguration there is good visibility of opposing traffic. this movement is quite heavy and i am searching for ways to increase it effeciency and capacity. this single movement influences the green band for thru traffic both directions as i must keep it from backing traffic thru the other intersection.
Currently running four intersections with dual left turns and protected/permitted phasing. None of the intersections have an opposing left turn movement to the dual left turn and all have at least two thru lanes in the opposing phase.
One has been in operation for over 10 years, another for about 2 years and the last two were activated this past January.
We have not had any citizen complaints referenced to this type operation and I am not aware of an accident history that would require modification of the operation.
We are replacing a single left turn lane with a double-left turn lane and need to shift the through lanes to the right to make room. What taper rate is needed to shift these lanes over?
