Supervisors recertify Gum Tree Lane speed limit for radar enforcement

The 35 mph speed limit on Gum Tree Lane between Stage Coach Lane and Hamilton Lane has been recertified for radar enforcement.

A 5-0 San Diego County Board of Supervisors vote February 26 approved the radar recertification for the 0.76-mile segment. “We need to make sure that law enforcement has all the necessary tools available to them in order to keep our roads safe,” said Supervisor Bill Horn. “Recertifying Gum Tree Lane’s 35 mph speed limit for radar enforcement will allow officers to continue to use radar guns to measure the speed of vehicles and take action as necessary.”

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. The speed limit can be reduced by an additional 5 mph if findings of special circumstances not apparent to a typical motorist are made.

Periodic recertification, along with a supporting speed survey, is required for continued radar enforcement. The county’s Department of Public Works or DPW contractors perform speed surveys every seven years on road segments which have been certified for radar enforcement.

No special findings were made to maintain the 35 mph speed limit, although rounding issues led to a statistical 85th percentile speed of 40 mph with the speed limit being rounded down from just under 40 mph. Thirty-seven of the 247 drivers in the speed survey were at 41 mph or above, seven drove at 40 mph, and the other 203 were below 40 mph.

Gum Tree Lane between Stage Coach Lane and Hamilton Lane also includes a school zone associated with Frazier Elementary School. The 25 mph speed limit in the school zone when children are present is automatic and does not require a speed survey for radar enforcement.

Gum Tree Lane is a striped two-lane roadway which varies in width from 27 to 44 feet. It is classified as a Light Collector on the Mobility Element of the county’s general plan.

A traffic survey taken in October 2013 east of Stage Coach Lane indicated a two-way average daily volume of 3,470 vehicles. The previous traffic surveys on Gum Tree Lane were taken west of Hamilton Lane; the November 2006 traffic survey indicated an average volume of 1,400 vehicles while an average of 1,490 vehicles was the result of a February 2000 survey. During the five-year period from July 31, 2008, to July 31, 2013, four collisions were reported along Gum Tree Lane between Stage Coach Lane and Hamilton Lane.

The speed surveys for Gum Tree Lane were conducted 900 feet east of Stage Coach Lane. The 2006 survey indicated an 85th percentile speed of 38.8 mph with 72.9 percent of drivers traveling within a 10 mph pace of 31-40 mph. DPW student intern Geoffrey Retemeyer conducted the Oct. 21, 2013, speed survey of the 247 vehicles crossing the survey point between 12:21 p.m. and 1:43 p.m.

Although the 85th percentile speed rose to 40 mph, the 10 mph pace was still 31-40 mph with 163 motorists, or 66 percent, traveling within that pace. The fastest driver was traveling at 51 mph while the slowest motorist drove at 23 mph. The most common speed, with 27 drivers, was 36 mph.

The county’s Traffic Advisory Committee had recommended recertification during the TAC’s Dec. 13 meeting.