TAC recommends lower Alturas Road speed limit

Joe Naiman

Village News Reporter

The county's Traffic Advisory Committee has recommended that the speed limit on Alturas Road south of Fallbrook Street be lowered to 30 mph.

A unanimous TAC vote Oct. 22 recommended that the San Diego County Board of Supervisors reduce the current 35 mph speed limit due to an accident rate more than four times the statewide average for similar roads. The county supervisors are scheduled to hear the speed limit issue March 2.

"We can easily justify the 30 miles per hour," said county traffic engineer Zoubir Ouadah.

In order for a speed limit to be enforceable by radar, a speed survey must show that the speed limit is within an adjacent 5 mph increment to the 85th percentile speed. Periodic recertification, including a supporting speed survey, is required for continued radar enforcement and the county's Department of Public Works or a DPW contractor typically conducts speed surveys every seven years.

The speed limit may be rounded either up or down from the 85th percentile speed. The speed limit may also be rounded down an additional 5 mph if findings are made that the road has conditions which would not be apparent to a motorist unfamiliar with the road. If speed surveys are taken at more than one location along a reviewed segment a "speed zone" for the entirety of the speed surveys can be used.

Alturas Road from Fallbrook Street to the end south of Ali Way measures 1.20 miles. The striped two-lane roadway has a solid double yellow centerline which prohibits passing and intermittent white edge lines. It is not classified on the mobility element of the county's general plan. The pavement width ranges from 20 to 40 feet. A traffic signal exists at the intersection of Alturas Road and Ammunition Road. The existing 35 mph speed limit has been certified for radar.

"It is very residential in nature. There's a lot of multi-family. It's pretty high-density," said DPW senior civil engineer Ernie Bartley.

Bartley noted that Clemmens Lane Park and a shopping center are close to Alturas Road. "A lot of the folks who live on Alturas do walk," he said.

Many motorists utilize Alturas Road, including intersections, to commute. "Camp Pendleton is right there on Ammunition," Bartley said.

An October 2020 traffic survey taken 900 feet south of Clemmens Lane produced an average daily volume of 2,753 vehicles consisting of 1,388 southbound drivers and 1,365 northbound motorists. A May 2021 traffic survey 190 feet north of Alturas Lane had a volume of 4,436 drivers with 2,545 traveling northbound and 1,891 driving southbound.

May 27, 2021, traffic surveys were taken 190 feet north of Alturas Lane and 900 feet south of Clemmens Lane. The 151 drivers in the speed survey 190 feet north of Alturas Lane had an 85th percentile of 36.1 mph with 76.0 percent within a 10 mph pace of 28-37 mph. The speed survey 900 feet south of Clemmens Lane measured 228 drivers with an 85th percentile of 37.1 mph and 71.0 percent of drivers in a 26-35 mph pace. The 85th percentile for the speed zone was 36.6 mph with 73.5 percent of the drivers within a 27-36 mph pace.

During the 36-month period from June 1, 2018, to May 31, 2021, Alturas Road between Fallbrook Street and the end had 23 reported collisions including three in which an injury occurred. The collision rate is 6.51 per million vehicle miles. The statewide average for similar suburban two-lane roads with speed limits under 45 mph is 1.60 per million vehicle miles.

"The data justifies it," Ouadah said of lowering the speed limit.

"I think it's a smart move," said Matt Wellhouser, who is the TAC's public member for the third and fifth supervisorial districts.

Improper turning caused six of the collisions. Right-of-way violations were responsible for five collisions. On three occasions a motorist ran the traffic signal at the intersection of Alturas Road and Ammunition Road, which accounted for seven of the total collisions. Two collisions apiece were caused by driving under the influence, unsafe speed, and driving on the wrong side of the road. Unsafe starting or backing caused one collision. The cause of two collisions was not determined.

Only 17 of the 379 drivers in the speed survey were traveling 6 mph or more above the existing 35 mph speed limit. "In general people do obey the signs," Ouadah said.