Sensors could offer gridlock solution
By: Mike Aldax
May 11, 2009
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Wireless sensors will be installed at busy intersections around the City in an effort to improve the timing of traffic lights and ease the flow of traffic and transit. (Examiner file photo)
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SAN FRANCISCO — Gridlock at some of the busiest intersections in The City will be eased with a plan to modernize how traffic signals are timed.
The signal-timing system at more than 100 city intersections is “defective,” difficult to fix when it breaks down and often goes unrepaired for long periods, according to a report from the San Francisco County Transportation Authority.
The system includes underground wiring strung across side streets that trigger a signal change when a vehicle rolls over it. The wires are “embedded in the pavement, and therefore require invasive maintenance when they fail,” the report said.
The San Francisco Municipal Transit Agency, which oversees the system, “has not been able to keep up with the maintenance,” it said.
When the wires aren’t replaced, the lights on the busy corridors continue to turn red even when there is no traffic on the smaller side streets, the report said.
To ease congestion on the busiest streets — particularly along carrying popular Muni lines — The City plans on installing a modern wireless timing system at eight popular intersections, including 19th Avenue and Sloat Street, Lombard and Pierce streets, and three intersections along the Embarcadero.
The system involves embedding wireless sensors in the pavement that can “sense a disturbance in the Earth’s magnetic field as vehicles travel over them.” The sensors then send a wireless signal to trigger the lights.
Any repairs or fine-tuning of the system would happen in an aboveground control box located at intersections, the report said.
The system is “fast,” “easy to install,” “more reliable, and requires less maintenance,” the SFCTA said.
Along with easing congestion for cars, the new system would speed up a number of important Muni routes, including the N-Judah, which is The City’s most-used line with more than 40,000 weekday passengers.
Last week, the transit agency reported an on-time performance of 74.5 percent, its best in recent memory but below its voter-mandated goal of 85 percent.
“This small project is part of a much broader effort to reduce delays along our busiest Muni corridors,” said Muni spokesman Judson True.
Muni has been working to adjust signal timing across The City to favor buses and streetcars. Timing improvements cut down travel time and delays along heavy downtown corridors by as much as 10 percent, according to the Metropolitan Transportation Commission, which has been encouraging such improvements for all Bay Area cities.
The SFCTA is expected to vote on approving the funding for the project during a Tuesday meeting.
Intersections that will receive new sensors:
19th Avenue and Sloat Street
Fifth and Brannan streets
Sixth Avenue and Fulton Street
18th Avenue and Fulton Street
Embarcadero and Folsom
Embarcadero and Kearny/North Point streets
Embarcadero and Washington Street
Lombard and Pierce streets
Muni lines to see fewer delays
F, KT, N, 5, 10, 21, 28, 28L, 29, 43, 47 and 76.
Source: San Francisco County Transportation Authority
maldax@sfexaminer.com
