'Smart' traffic signals may help traffic 'Smart' traffic signals may help traffic (December 05, 2003)

Proposal would aid Charleston corridor redesign

by Don Kazak

A key to improving traffic flow along the much-discussed Charleston/Arastradero road corridor may lie in something people aren't really discussing, but has the city's hope's high: Smarter traffic signals.

The city has applied for a $1.2 million grant to install what's called "traffic adaptive" signals along the corridor.

"We were told it was the most important thing we can do in the corridor," said Mayor Dena Mossar.

The traffic-adaptive system uses video or pavement sensors to digitize information and send it to a computer that makes instantaneous decisions on how long traffic lights should stay red and green. In other words, the system adapts to the traffic flow.

The city's Planning and Transportation Commission will meet Wednesday night to mull over staff recommendations for the Charleston corridor, with the City Council scheduled to make a final decision in January. All the attention thus far has been on the plan to reduce the lanes from four to three -- two through lanes and a median with left-turn pockets. The plan has caused some public consternation.

But the number of traffic lanes can be reduced and traffic can flow more smoothly, insists Joe Kott, the city's chief transportation official. The traffic-adaptive system, by itself, will increase efficiency by up to 20 percent.

For drivers, that means shorter waits at red lights, and less congestion at intersections.

It's an expensive, high-maintenance system because the sensors have to work perfectly and must be replaced if things go awry. "But you get a heck of a lot more efficiency, with the signals re-timing themselves," Kott said.

The "smart" signals would replace what the city has now, except for left-turn movements at intersections that are triggered by road sensors -- timed signals which don't change to adjust to traffic flow. The signals are on different timing cycles for peak hours and off-peak hours, but the cycles are essentially inflexible.

Moving to traffic-adaptive signals is key to making traffic move more efficiently through the Charleston/Arastradero corridor, even with the proposed lane reductions.

Kott is hopeful that the city will win grants to fund traffic-adaptive signals not only for the Charleston/Arastradero corridor, but also on Middlefield Road and the residential portions of University Avenue and Embarcadero Road.

"This is cool stuff," he said, "and the funding agencies know the best way to add (road) capacity is electronically," instead of tearing up streets.

On his wish list, Kott would later like to add Alma Street and Lytton Avenue.

Any traffic control system is complicated, regarding sophisticated software, because of cross-streets and the need to keep traffic flowing smoothly on them, too, not just up and down a corridor like Charleston/Arastradero.

Beyond getting the grants for the traffic adaptive system, other upgrades are already on the way, with Alma scheduled to get better signal coordination and the Santa Clara County planning signal upgrades for Oregon Expressway/Page Mill Road, which is a county road.

The city has to work its own signal improvements hand-in-hand with the county's control of Oregon/Page Mill, and the state's control of El Camino Real, which is a state highway.

But Kott is confident all that coordination can happen.

The Planning and Transportation Commission meets at 7 p.m. Wednesday at City Hall.

-- Don Kazak can be e-mailed at dkazak@paweekly.com

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