Friday, July 30, 2010

Denton, Texas traffic engineer: "The cyclist should consider actuating the pedestrian push button."

Amazing quote from the Head Traffic Engineer in Denton, Texas that pretty much sums up the infrastructural corner we've painted ourselves into. Behind all the technical smoke-and-mirror excuses lies a simple unwillingness to question the wisdom of initial urban design mistakes made long ago.
"It is worth noting that there are no known published national, TxDOT or regional metro policies/standards/guidelines/etc concerning what a "safer" timing is for a bicyclist at a signalized intersection. There are substantial timing and traffic mix/volume variations at every intersection in Denton, further complicating a determination of what a "safer" timing might be that would not only be beneficial to a cyclist but also be defendable in the event of litigation.

Inductive loops are installed in the pavement, and an electrical current is sent through it to set up a magnetic flux, which when passed over by a ferrous material, disrupts the flux and in so doing the controller "assumes" there is an object that needs to be serviced. The problem with this technology with regard to a bicycle is that with more and more bikes being made mostly of aluminum, polycarbon, composites and the like, there is less and less iron in the bicycle to be detected. Even specialized inductive loops installed near the gutter exclusively for bikes are becoming more and more ineffective. That is why on heavily traveled bike routes, some "bike friendly" agencies are beginning to install bike push buttons (works the same as the pedestrian push buttons mentioned herein above). Standard vehicle loops are installed in the middle of a travel lane and are typically four to six feet wide. Therefore, a cyclist that is riding near the gutter, even if he is on a bike that has enough iron in it to be detectable by the loop, would not be picked up because he would be outside the detection zone. Because of the likelihood of a bicycle not being detected, even if it occupies an inductive loop, one would have to add green time to each phase and cause it to happen continuously (24/7). For a random and infrequent event, this means that the controller cannot cycle as fast and therefore will cause delay (lost time) and greater pollution (because of the greater vehicle idling) for the cross street traffic, thus defeating the benefits of the bicycle. Placing a "T" marking for a standard vehicle detection zone would require a cyclist to occupy the center of the travel lane, placing them at greater risk with vehicles doing the same thing. The detection of the bike would be suspect and so could cause the phase to be skipped because a vehicle with enough iron was not on the loop, creating further issues.

For these reasons, rather than attempting to modify signal timings and equipment to accommodate this highly variable demand, it might be preferable to provide public education indicating that if a cyclist is concerned about the amount of green time that might be provided at any particular intersection because of little or no vehicle activations, that cyclist should consider actuating the pedestrian push button for the signal, thereby obtaining more green time for crossing the street. This type of public education could be provided on the City’s website, possibly on DTV or on one of the local bicycle advocacy web pages."

Via Google Groups.

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