A matter of traffic lights and timing


Southeast / Virginia 21 Views

Most of the queries lately have been about traffic signals — why some take so long to change, why some change randomly, potential malfunctions.

The setting of signals involves quite a bit of research on traffic patterns at particular times, pedestrian use, coordination with other lights and other factors.

But the perception of drivers and pedestrians is another matter entirely, said Emmanuel Posadas, Gainesville’s traffic operations manager.

“Time/space perception varies depending on ... the mode of travel, or sometimes trip purpose — say leisure versus being late to an important event. If a user’s consumption of time/space is 35 to 45 mph, a 30 second delay may be ‘too long’ for that user,” Posadas said. “While if a user’s consumption of time/space is four feet per second as a pedestrian, a 30 second crosswalk time may ‘too short’ for that user. Generally the individual is only concerned with his travelled path, while our team is concerned with all (traffic) movements and all modes of travel, with safety being the No. 1 priority.”

With that out of the way, Posadas responded to an email from Dave Hill about the light at Northwest 39th Avenue and 51st Street.

Hill speculated a malfunction from 6:45 to 6:55 a.m. was keeping the light from turning green for northbound 51st Street drivers, adding that school buses wanting to turn right will sometimes be stuck for 10 minutes or more.

“ ... most people who are aware of the fact that this light will not turn green will drive through the parking lot and go around Northwest Grille to exit on 39th Avenue,” Hill wrote. “I believe the driver of the school bus is not allowed to make right turns on red, and there’s a malfunction in the signaling device that prevents a solid green from turning on to allow traffic to go through the intersection or to turn right. Until this is fixed my friends will continue to drive to the parking lot to get onto 39th Avenue to proceed east.”

Posadas said that at certain times the signal is programmed to change at regular intervals, which are set to minimize the wait time. During the time Hill mentioned, the signal programming transitions to intervals that coordinate with other signals to keep traffic moving.

“Some transitions occur within two to three minutes (with one to two signal cycles), some as long as 10 minutes (five signal cycles),” Posadas said. “Those periods ... are not signal malfunctions. Going from one programming mode to another takes a couple of minutes to ensure safety of all users.”

Posadas added, “As our community grows, and our roadway capacity remains the same, road users will have to adjust their habits and plan adequately for travel time. Drive as safe and as courteous as best they can — saving a couple of minutes in travel time is not worth the safety risk.”