Police chiefs throughout the Bay Area are protesting a proposed change to speed limits that they say could result in drivers going faster and faster on residential streets and getting into more accidents.
The rule change, recommended by an advisory committee to the California Department of Transportation, would use a new formula to calculate speed limits.
The proposal would also curtail the freedom that cities and law-enforcement agencies have to set speed limits in their jurisdictions.
Under the current law, speed limits are set at what is called the 85th percentile — the speed that separates the slower 85 percent of motorist speeds from the fastest 15 percent.
Cities have some flexibility in setting the limits. They could round down to get to the nearest 5 mph if conditions call for it, or round up to make numbers even (from 29 mph to 30, for example). The lower speed could be justified by collision records, traffic, residential density, pedestrian, bicycle safety and roadside conditions, according to Laura Wells, deputy director of transportation and parking operations for the City of San Jose.
But the proposed change would put a 50th percentile "floor" in place that caps the slowest speed at what 50 percent of drivers do. If, on a residential street, the speed limit is posted at 25 mph, but the 50th percentile is 26 mph, the new speed limit would have to be rounded up to 30, according to Wells.
"You have to go to the higher speed," she said.
The committee believes the speed should be set close to what the majority of motorists are driving, Wells said.
"It's a mathematical exercise versus an engineering judgment," she added. "They have taken away the ability for local agencies to use engineering judgment."
Speed limits on many Palo Alto streets could be much higher if the change goes through, according to Palo Alto Police Chief Lynne Johnson.
"If this language is approved, our cities would be forced to increase the posted speed limits on many of our streets," she said. For example, San Jose would have to increase the limits on more than 266 streets and Sunnyvale would need to increase limits on 63 percent of its streets.
"This most certainly will lead to more accidents as most residential streets are not able to handle those speeds," Johnson said.
Johnson said she has asked the city's transportation division to work up the number of streets that could be affected. She said she can't yet put a figure on what costs might be to the police department or the city, but costs in officer time to respond to accidents could go up.
Wells said cities are already strapped due to budget cuts and will need to spend more money to install additional traffic-calming devices, such as speed bumps and traffic tables.
Police see another wrinkle that could be caused by the rule change.
The speed-limit adjustments won't be a one-time thing, and that is deeply concerning, according to Lt. Jeff Smith, assistant to San Jose police Chief Robert Davis.
"If this change takes place, speeds will creep up. After seven years, when surveys need to be rewritten, we can expect that the ... floor will increase yet again," he said.
Caltrans officials did not return phone calls asking for comment on this article. A hearing on the recommendations will take place in San Francisco on Thursday.