Joel Fitts, Senior Traffic Engineer
Post Number: 36
|Posted on Tuesday, April 28, 2009 - 01:24 am: |
Unfortunately, we are limited in what we can do with the signal timing at this intersection until TxDOT's reconstruction of Eldorado Parkway provides us with additional lanes. Without left-turn lanes in any direction, we cannot run a more efficient signal timing pattern. And with only one lane in each direction, we are forced to provide green time in proportion to the volume on each approach.
We continually monitor the intersections along Eldorado Parkway and adjust the signal timing in order to equalize the delay experienced by every direction. We cannot create more green time and, without adding a lane, we cannot eliminate delay (delay can only be shifted to one direction or the other). Because there is so much more traffic on Eldorado, it is given longer green times than Teel; however, the total delay in each direction is about the same. In a simplified example, if there are 500 cars on Eldorado which experience 60 seconds of delay each, that is equivalent to 100 cars on Teel which experience 300 seconds of delay each:
500*60 = 100*300
Why don't we ensure that each individual car on each approach experiences the same delay (in this example, 100 seconds)? Because making the larger volume of traffic on Eldorado wait that much longer each cycle would cause traffic on Eldorado to form longer and longer queues until traffic backed up into other intersections and/or traffic signals, causing gridlock. Unfortunately, in a contrained situation such as this, it is the direction with the least traffic that must be given the shortest amount of green to avoid gridlocking the major street.
Once the TxDOT project is complete, Eldorado and Teel will both have additional through lanes as well as left-turn lanes, which will dramatically reduce the delay for all directions, especially for individual cars on Teel Parkway. Even before completion of the project, conditions at this intersection will improve as soon as an additional lane is made useable on Eldorado. In the meantime, we will continue to monitor the constrained intersection and make periodic adjustments to equalize the delay.
Senior Traffic Engineer