You Can Go Faster, if 85% of Drivers Say So

Commuters, start your engines.

During the next few months, Thousand Oaks officials plan to increase speed limits on some city roadways. But don’t expect your favorite 35-mph zone to become a 55-mph zone overnight.

“We’re probably talking about 5-mph adjustments,” said Don Nelson, the city’s public works director.

Every five years, the city conducts traffic surveys to find the optimum speed for safe driving. The surveys--which should be completed early next year--measure how fast vehicles travel on a particular roadway. The speed at which 85% of those vehicles travel is considered safe for that street.

“You have to set [the speed limit] within 5 mph of the 85th percentile on that street,” Nelson said. “To set a limit lower than that is actually instituting a speed trap.”

Nelson said the city has about 136 street segments with speed limits more than 5 mph lower than the 85th percentile. That means a motorist ticketed on one of those segments by an officer using a radar gun could successfully challenge the citation in court.

Traffic surveys serve as a backup for officers, said Sgt. Patti Salas of the Thousand Oaks Police Department’s traffic bureau. “It’s important for our streets to be in compliance so we can do effective enforcement,” she said.

The city will look at major arterial and secondary streets, said Jim Mashiko, a senior civil engineer in the city’s traffic division.

“They’ve gone to court on a couple of these streets and the judges have dismissed citations,” Mashiko said.

No streets have been officially designated for speed-limit increases yet.

To measure traffic speeds, surveyors use radar guns on vehicles during off-peak hours.

“We try to be out of view of the approaching motorist,” Mashiko said. “Usually, we will try to get a sample of 100 vehicles.”

For the survey, longer roads are split into half-mile or mile-long sections to determine if speeds vary.

“We try to break them down into smaller segments,” Mashiko said.

Once the new limits have been approved, the city will send its cache of blank speed-limit signs to Northern California to be marked, Nelson said. Other signs may simply be updated with stickers.

Residents should not be concerned that traffic will move much faster once the city posts the new limits, Salas said.

Years ago, Salas patrolled Avenida de las Flores between Moorpark and Lynn roads. The posted limit was 35 mph, but most of the traffic moved along safely at about 45 mph, she said.

Even if the speed limit on that section of road increases to 45 mph, most of the traffic will remain at that speed, Salas said. People traveling on that roadway at 65 mph will not be encouraged to drive faster by a higher posted speed limit, she said.

“They would have been doing it if it was still posted at 35, because they’re on a mission to get somewhere quickly,” she said.

The increases in Thousand Oaks can be comparable to speed increases on California’s freeways. When the speed limit was 55 mph, many drivers traveled safely at 70 mph. When the speed limit increased to 65 mph, traffic did not make a jump to 80 mph, Salas said.

The city plans to work with Caltrans to amend some aspects of the 85th-percentile requirements, Nelson said. For instance, even if a survey indicates that drivers feel safe at 65 mph on a Thousand Oaks street, the city is not likely to allow that speed.

“That’s just flat-out too fast for city streets,” he said. “The real issue for us is roadway safety.”