TAC recommends signal for S. Mission Road and Green Canyon Road

The county's Traffic Advisory Committee (TAC) has recommended that the intersection of South Mission Road and Green Canyon Road be placed on the county's Traffic Signal Priority List.

Brian Hadley of Caltrans abstained when the TAC voted on the proposal Oct. 28, but the other eight members present voted in support of the signal. The San Diego County Board of Supervisors must make the actual decision to approve a future signal at the intersection and will likely consider the TAC recommendation at the supervisors' Jan. 11 meeting.

"It's the right type of road for a signal," said TAC secretary Kenton Jones.

South Mission Road is a two-lane through highway which is 50 feet wide north of its intersection with Green Canyon Road and 45 feet wide south of that intersection. South Mission Road has edge striping along both sides of the roadway as well as median striping, and a left turn pocket at the intersection allows southbound traffic to turn onto Green Canyon. The speed limit on South Mission Road at Green Canyon Road is 50 mph. South Mission Road is classified as a Boulevard in the Mobility Element network of the county's general plan.

Other than the stop sign where Green Canyon Road ends at South Mission Road, Green Canyon Road is also a two-lane through highway with median striping and edge striping on both sides. Green Canyon Road is classified as a Light Collector in the general plan's Mobility Element. It is approximately 30 feet wide, and no speed limit has ever been formalized.

A multi-day October 2014 traffic survey revealed a two-way average daily volume of 10,570 northbound vehicles on South Mission Road south of Green Canyon Road, 10,230 southbound vehicles on South Mission Road north of Green Canyon Road, and 1,160 westbound vehicles on Green Canyon Road east of South Mission Road. The previous traffic survey at that intersection was taken in August 1995, when the average daily volume was 9,240 northbound, 7,960 southbound, and 640 westbound vehicles.

"It has grown volumetrically over the years," Jones said.

The proposed signal was slated to be discussed during the TAC's December 2014 meeting but was pulled off that agenda to allow the Fallbrook Community Planning Group to provide input. Although the intersection met signal warrants in 2014, the community planning group was concerned about potential adverse impacts to the traffic flow and recommended that the county's Department of Public Works (DPW) consider potential alternatives to signalization including exploring line-of-sight concerns, straightening the road at that intersection, additional turn lanes, and flashing lights.

DPW agreed to conduct a field review, including sight distances, and then return the matter to the planning group for further input. On April 18 the planning group unanimously endorsed the signal in conjunction with requests for review of potential traffic calming and sight distance improvement measures.

DPW did not conduct a new traffic volume survey between the preparation for the December 2014 meeting and the October 2016 meeting, although the collision data was revised. The December 2014 consideration used a 67-month period from January 1, 2009, to July 31, 2014; during that period four collisions, including two which involved injury, were reported. During the 62-month period between January 1, 2011, and February 29, 2016, six collisions were reported at the intersection.

The intersection meets volume warrants for a signal but not collision warrants, which are often the result of drivers gambling that enough space exists between the intersection and the through traffic with the right of way.

"They're making good decisions," said Jones. "They're being patient and they're waiting."

The intersection meets the eight-hour vehicular volume, four-hour vehicular volume, and roadway network warrants for a signal. The eight-hour volume warrant for a rural intersection with a single approach lane requires eight separate hours with at least 525 vehicles on the major street and 53 vehicles on the minor street; the intersection of South Mission Road and Green Canyon Road meets that criteria for the hours beginning at 6:00 a.m., 7:00 a.m., 8:00 a.m., 9:00 a.m., 11:00 a.m., 3:00 p.m., 4:00 p.m., and 5:00 p.m. The four-hour thresholds of 350 vehicles for the major street and 84 vehicles for the minor street were met between 6:00 a.m. and 9:00 a.m. and between 4:00 p.m. and 5:00 p.m. The roadway network criteria include a minimum of 1,000 vehicles per hour, a highway system serving as a principal network for through traffic, a rural or suburban highway entering or traversing a town, and designation as a major route on an official plan.

"It does meet more than one warrant," said county traffic engineer Zoubir Ouadah.

The intersection did not meet the peak-hour delay, pedestrian volume, school crossing, coordinating signal system, crash, or railroad crossing warrants.