Re: Red Lights and Accidents

Larry G <gross.larry@xxxxxxxxx> wrote:

On Feb 9, 1:01 am, Guy Olsen <guypol...@xxxxxxxxx> wrote:
On Feb 8, 6:55 pm, John Lansford >

One thing the RLC's do stop is the "queueing" of traffic through the
intersection, especially if they're making left turns.  You see this
all the time; a line of cars starts making a left turn, and the
motorists at the end don't stop turning left even after the light
turns red.  RLC's stop that activity.

Capacity analysis takes such behavior into account under the term
"left turn sneakers".  Eliminating them reduces left turning capacity,
which adds to congestion and delay.  My sense is that left turn
sneakers/queuing are more likely to occur where left turn capacity is
already limited.

where it is limited and the cycle if fast - agree.. and you see this
where they are employing access management and signal sequencing.

One thing that has yet to be mentioned in any of the RLC threads is
the role that congestion plays in red-light violations.  I suspect
that signals where drivers have to wait for multiple cycles are more
prone to red light violations then those with better Levels of
Service.  Therefore, improvements that reduce congestion should also
reduce red light violations.  Of course, as engineering solutions go,
such improvements can be the most costly.

Another is the effect RLCs have on congestion.  As described above,
anything that reduces the number of vehicles that will clear an
intersection per cycle will increase congestion/delay.

most folks who are NOT familiar with the short left turn light will
just stop and be frustrated but the folks who ARE familiar with the
short light - will try to not get caught at the light.

You can see sometimes multiple cars trying to follow the last

But these do not cause T-Bone crashes since the ongoing traffic is
stopped and just starting again.

In my area - I've seen the left turners KEEP the green line traffic
from coming.

That's what I've noticed as well. In high capacity situations the
left turning traffic continues well into the green light phase,
blocking the intersection for those trying to go straight through.

John Lansford, PE
John's Shop of Wood