Survey reveals car volume -- not speed -- plagues LAH roads

Courtesy of town of los altos hills
The above graphic shows vehicle counts and speeds measured on Los Altos Hills streets.

While cut-through vehicles continue to clog Los Altos Hills’ streets, a recent traffic survey seems to suggest that interlopers, are, at least, not excessively speeding.

Data collected during the two weeks bookending a Santa Clara County Sheriff’s Office traffic enforcement operation in September reveal that drivers, on average, did not exceed 6 mph over the posted speed limit.

“When we spoke with Captain Rich (Urena), he said that the deviation from the posted speed limit and the actual speed isn’t that much,” said Public Works Director Allen Chen during an Oct. 11 city council presentation.

The survey is the town’s latest effort to combat commuters directed by navigation apps like Waze to use Los Altos Hills streets for avoiding traffic slowdowns, particularly the southbound Interstate 280 bottleneck at El Monte Road in the afternoon. Some residents who live off popular shortcuts including Purissima Road and Summerhill Avenue say they can’t pull out of their driveways at peak commute times due to the constant stream of cars. Some residents also have complained about speeders.

Officials in May erected “No Thru Traffic” signs at major arteries into town, but Sheriff’s Office representatives acknowledge that it’s difficult for deputies to enforce the rule because they don’t know if vehicles belong to residents or commuters without stopping them and consulting the drivers.

Measuring speed

The survey and traffic enforcement operation help quantify the problem.

The town paid approximately $7,800 for two traffic deputies to patrol Purissima, Elena, Fremont and Robleda roads 4-7 p.m. every Tuesday, Wednesday and Thursday in September. In that time, the deputies cited 19 Los Altos Hills residents and 63 nonresidents. The breakdown is 18 speed citations, 39 stop sign citations and 25 citations related to cellphone use or lane-violations.

To determine whether the enforcement operation impacted driver behavior, the town hired a traffic data collection firm for $2,650. The contractor used pneumatic road tube sensors to calculate vehicle volume and speed at locations on Purissima, Elena and Fremont roads 4-6 p.m. Tuesday, Wednesday and Thursday during the last week of August and then again the first week of October.

The data from southbound Elena Road at Josefa Lane, for example, revealed an average of 719 vehicles in two hours before the enforcement and an average of 824 vehicles in two hours after the enforcement. The posted speed limit at that location is 25 mph, and the average speed measured was 29 mph both before and after the enforcement.

At eastbound Fremont Road at La Paloma Road, the sensors registered an average of 685 vehicles in two hours before the enforcement and an average of 863 in two hours after. The posted speed limit at the location is 25 mph, and the average vehicle speed varied from 31 mph before the enforcement to 28 mph after.

Councilmembers discussed the results at the Oct. 11 council meeting.

“I’m reading that we really didn’t have much impact, except maybe on Fremont, right?” Councilman John Radford said. “It’s not that we wasted our money, but it didn’t really change the basic, you know, speed flow.”

Not so fast, Chen warned. The before-and-after vehicle counts may give the impression that cut-through traffic volume increased, but fewer vehicles are on local roads in August compared with October due to school closures and summer travel.

When asked whether the lower-than-expected vehicle speeds calculated are simply a reflection of too many vehicles on the roads – and not necessarily good driver behavior – Chen said it’s difficult to tell.

“At a few locations like before a stop sign-controlled intersection, the lower speed could be due to the increased number of vehicles,” he wrote in an email to the Town Crier.

At the very least, the traffic enforcement operation sent a message to drivers, Chen added.

“What the sheriff did was create the public perception that, hey, the town of Los Altos Hills is doing something to prevent a potential safety hazard,” he said.

On the encouragement of the council, Chen is exploring additional methods for traffic control and approaching regional partners such as Caltrans and the Santa Clara County Roads and Airports Department for guidance and cooperation.

“I’m still evaluating the possibilities,” he said. “I don’t have the answer right now.”

The topic is expected to appear on the Nov. 16 city council agenda.

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