Gum Tree Lane remains 35 mph for radar enforcement

The county’s Traffic Advisory Committee (TAC) recommended that the 35 mph speed limit on Gum Tree Lane between Stage Coach Lane and Hamilton Lane be recertified for radar enforcement.

The TAC’s Dec. 13 recommendation is expected to be ratified by the San Diego County Board of Supervisors on Feb. 26. The county supervisors can ratify, overturn, or amend a TAC recommendation.

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.

“The committee recommends continued radar enforcement of the posted 35 mph speed limit based on that review of current prevailing speeds and that radar certification is an effective tool against speeding, has a positive effect in reducing the speed of motorists, and Gum Tree Lane should continue to benefit from that enforcement,” said TAC secretary Kenton Jones.

The TAC did not make special findings to maintain the 35 mph speed limit, although rounding issues led to an 85th percentile speed of 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. None of the TAC members argued that the prevailing speed was 40 mph, so the speed limit was rounded down to 35 mph.

The 0.76-mile segment of 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 66.0 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.