The county’s Traffic Advisory Committee recommended a 30 mph speed limit on Rice Canyon Road and an all-way stop control at Rice Canyon Road and Rainbow Heights Road.
The TAC’s unanimous Oct. 27 recommendations are subject to San Diego County Board of Supervisors approval. A first reading and introduction of the ordinances for the radar-enforceable speed limit and all-way stop control is scheduled for the Jan. 10 Board of Supervisors meeting.
The second reading and adoption will likely take place Jan. 24, in which case the speed limit and stop requirement will become enforceable Feb. 23 although the county’s Department of Public Works (DPW) may post signage earlier.
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 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.
The TAC cited curves throughout the road, the lack of shoulder lanes, and an accident rate above the statewide average for similar roads as conditions which would warrant a 30 mph speed limit rather than a 35 mph speed limit supported by the speed survey.
The distance of Rice Canyon Road between State Route 76 and Eighth Street is 5.06 miles. The road does not currently have a posted speed limit. Currently a stop sign for southbound traffic exists at State Route 76 and a stop sign for northbound motorists is present at Rainbow Heights Road. Rice Canyon Road ranges in width between 20 and 24 feet and curve advisory warning signs are posted throughout the road, which also has a striped median.
Rice Canyon Road is classified as a Light Collector in the mobility element of the county’s general plan, but it also holds the unofficial classification of being a shortcut for Riverside County commuters who desire to avoid Interstate 15 including the secondary border checkpoint by using Rainbow’s surface streets.
“The community that lives in this area is not used to the influx of traffic,” said DPW traffic engineering manager Murali Pasumarthi.
An Aug. 3, 2017, traffic survey taken on Rice Canyon Road 405 feet south of Moon Ridge Road revealed a daily count of 1,139 northbound vehicles and 207 southbound vehicles. The volume included 335 northbound vehicles between 4 and 4:59 p.m. and 356 northbound vehicles from 5 to 5:59 p.m.
The Aug. 29, 2017, traffic survey taken at Rainbow Heights Road and Rice Canyon Road produced a daily volume of 1,068 westbound, 1,004 southbound, and 823 northbound vehicles. The highest hourly volumes for the westbound vehicles turning from Rainbow Heights Road to Rice Canyon Road were 85 between 8 and 8:59 a.m., 84 from 6 to 6:59 a.m., 83 from 7 to 7:59 a.m., and 82 between 2 and 2:59 p.m.
The one-hour period between 4 and 5 p.m. had the highest volumes both ways on Rice Canyon Road with 122 northbound and 105 southbound motorists.
The stop sign only for northbound traffic at the intersection was based on prevailing flow. “The volumes don’t really support this,”
said DPW senior civil engineer Ernie Bartley.
The increased volume of northbound traffic, in conjunction with a sight distance at the intersection of approximately 100 feet for motorists on Rainbow Heights Road, creates the risk of an accident. “We’re recommending a stop control pretty much based on the line of sight distance,” Bartley said.
Rainbow Heights Road, which is not classified in the mobility element, is 20 feet wide at the intersection. Rice Canyon Road is 24 feet in width at Rainbow Heights Road.
During the 67-month period from Jan. 1, 2012, to July 30, 2017, Rice Canyon Road between State Route 76 and Eighth Street had 38 reported collisions including 18 which involved injury and one which resulted in a fatality.
The rate of 2.74 collisions per million vehicle miles exceeds the statewide average of 1.4 collisions per million vehicle miles for similar two-lane roads with speed limits under 55 mph.
The two collisions at the intersection of Rice Canyon Road and Rainbow Heights Road, neither of which involved injury, created a rate of 0.34 collisions per million vehicles crossing; the statewide average for similar intersections is 0.16 collisions per million vehicles.
DPW consulted with the Rainbow residents about the potential all-way stop control. “At first they were kind of hesitant,” Bartley said. “After we went through it they were very supportive.”
National Data and Surveying Services conducted two Aug. 3 speed surveys on Rice Canyon Road. The survey 405 feet south of Moon Ridge Road was taken between 11 a.m. and 1 p.m. and the 59 vehicles had an 85th percentile speed of 38 mph with 76 percent of
the vehicles within a 10 mph pace of 29-38 mph.
The fastest vehicle traveled at 43 mph, the two slowest motorists crossed the survey point at 25 mph, and six motorists apiece made 31 mph and 38 mph the most frequent speeds while five drivers apiece traveled at 29 mph, 30 mph, 32 mph, and 34 mph.
The speed survey 420 feet north of Clearwater Road was taken between 9 and 11 a.m. and involved 53 vehicles with an 85th percentile of 39 mph and 64 percent of drivers within a 25-34 mph pace. The fastest driver traveled 44 mph, the slowest vehicle had a speed of 21 mph, and the most common speeds were 31 mph with six motorists and 30 mph and 28 mph with five motorists apiece.