Boise State Bicycle Congress

Making Idaho More Bike Friendly

By Sharon Fisher, 4-20-07

Traffic planners and designers in the Treasure Valley may be able to make future roads more bicycle-friendly thanks to information they learned today at the Bicycle Congress, held at Boise State University.

Speakers from the San Francisco Bay Area and Silicon Valley talked about concepts such as traffic lights that sense bicycles in an intersection and extend the green light accordingly, as well as changing the configuration of roads to reduce the incidents of “dooring,” or a bicyclist riding into an open door of a parked car.

Attendees at the conference included representatives from the Ada County Highway District, Idaho Transportation Department, and Capital City Development Corp., leading bicycle advocates to hope that these innovations might be implemented in Idaho at some point.

Ananth Prasad, an engineer for Santa Clara County, in California, reported on the county’s research and implementation of a dedicated cycling lane and a five-loop sensor that let the traffic signal know when a bicyclist was in the lane. When the light was red or yellow, the next green light would be longer, to give the bicyclist time to get across the intersection. If the light was already green, the light would stay green longer.

ACHD attendees indicated that the type of traffic signalling system used in Santa Clara county was the same as used in Ada County, meaning that the system has the capability of performing the same function here.

However, traffic laws in Idaho for bicyclists are different from the ones in California. For example, here bicyclists are allowed to stop at red lights and then go if there is no traffic. Similarly, bicyclists are allowed to treat stop signs as yield signs, if traffic levels warrant it. Consequently, the system would require some modification to be implemented in Idaho.

The system is implemented at 25 intersections in Santa Clara County, and is expected to be added to 150 intersections over the next five years as those roads are maintained, Prasad said. Putting in the inductive loops—which are sensitive enough to work even with a carbon bicycle, assuming it has a metal chain—costs about $8,000 per intersection, he said.

Interestingly, Ada County is already using such loops at approximately 270 intersections so bicycles and motorcycles can change the signal. However, a brochure put out by the county says that carbon or composite bikes might not set off the detectors. The brochure directs riders to place their bikes on a yellow splotch or the cut marks on the pavement where the device was installed to help improve its performance. “ACHD cannot simply turn up the sensitivity of the detector because it will sense vehicles in the next lane over,” the brochure says. Prasad said the ACHD system may use fewer loops than the Santa Clara County system.

ACHD’s brochure said the county is planning to change to a video detection system when the technology improves; Prasad said Santa Clara County had chosen its system over video detection due to problems detecting bicyclists during fog or darkness.

The city of San Francisco studied changes in the configuration of parking lanes and bike lanes to help reduce dooring, which resulted in 8% of bicycle accidents there from 2001 to 2005, said Dustin White, bicycle facility engineer for San Francisco Municipal Transportation. Widening parking lanes from 7 to 9 feet reduced the amount of space an open door took up in a bike lane from 50% to 10%. He also studied parking behavior and learned that wider lanes did not lead to cars parking further away from the curb.

To help change cyclists’ behavior, White also studied extending the “T” symbol that marks the beginning and end of metered parking spaces in San Francisco from 9 feet to 11 feet. This led cyclists to move from 10.11 feet to 10.4 feet from the curb, and leading 90% of them to ride outside the door zone, compared to 24%. He is also planning to study reducing bike lanes from 5 feet to 4 feet, giving the additional foot to the parking lane and reducing the time a door is open into the bike area without requiring additional street space.

ACHD will next week put up on its web site a survey to help it produce the Ada County Bicycle Master Plan. In addition, the department will count bicyclists at 40 intersections around the county.

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