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Home My WebLink About2006-01-09; Traffic Safety Commission; ; Investigate the need for a STOP sign on Llama Street at its intersection with Corintia StreetCITY OF CARLSBAD TRAFFIC SAFETY COMMISSION STAFF REPORT COMMISSION MEETING OF: January 9, 2006 LOCATION: INITIATED BY: Llama Street at C01intia Street Erica Leah, via e-mail ITEMNO. 6A REQUESTED ACTION: Investigate the need for a STOP sign on Llama Street at its intersection with Corintia Street. BACKGROUND: Llama Street intersects Corintia Street in a T-intersection configuration. This intersection is located in a residential area immediately adjacent to La Costa Meadows Elementary School with Llama Street being the stem of the T (see Exhibit 1). No STOP signs have been installed to assign the right-of-way at this intersection. DATA: Llama Street and Corintia Street are both considered local streets and they are not classified on the Circulation Element of the General Plan. STOP sign requests received by staff results in a traffic study being undertaken and the issue is reviewed carefully. Unnecessary STOP signs can cause substantial inconvenience to drivers and should be used only where watranted. One of the conditions at an intersection that may watrant consideration of installing a STOP sign on the minor street is when the safe approach speed to the intersection is less than 10 miles per hour. The safe approach speed to the intersection on the minor leg is typically evaluated when there is a request to install a STOP sign on the minor street at an intersection. The minor street at a T-intersection is generally considered to be the stem of the "T" with the major street being the top of the "T". Drivers approaching an uncontrolled intersection having th:ree or four legs have the right-of-way assigned based upon the rules of the road. However, the vehicle operator should have an unobstructed view of the entire intersection and sufficient length along the intersecting street for the driver to anticipate and avoid conflicts with approaching vehicles. A driver on the minor street (stem of the "T") when approaching the major street reaches a decision point when braking to a stop is necessary if there is another vehicle moving towards the intersection on the major street that may constitute a conflict. The decision point on the minor street must allow the driver to view to the driver's right and left, an approaching vehicle on the major street. The driver on the minor street, generally not having the right-of-way, can then slow, stop, or avoid a conflict with other vehicles, as necessary, when the proper clear sight triangle is provided (see Exhibit 2). CITY OF CARLSBAD TRAFFIC SAFETY COMMISSION STAFF REPORT COMMISSION MEETING OF: January 9, 2006 (continued) ITEMNO. 6A For local streets, the minor street decision point is assumed to be 50 feet from the intersection for a vehicle on the minor street traveling at an approach speed of 10 miles per hour. In general, a distance of 155 feet (stopping sight distance for 25 mph) along the major (local) street needs to be provided to minor street drivers to view vehicles approaching the intersection. However, when the grade of the major street exceeds three percent, grade adjustment factors are applied to the sight distance. In the subject case, the major street grade on Corintia Street is 1.0% east of the intersection and 2.5% to the west. Therefore, no grade adjustment factor is required to be applied to the sight distance length on Corintia Street. At the subject intersection, the driver on the minor street, Llama Street, has adequate sight distance to view approaching westbound major street (Corintia Street) vehicles when they are approximately 250 feet east of the intersection. However, eastbound vehicles approaching from the west on the major street (Corintia Street) cannot be seen at a point 155 feet west of the intersection due to the vertical alignment of Corintia Street and the elevation of the private property on the southwest comer of the Corintia Street/Llama Street intersection. A driver on Llama Street has sight distance for approximately 134 feet to the west when viewed from the decision point. Consequently, the 10-mile per hour safe approach speed criteria is not being met and a STOP sign can be considered for installation on Llama Street. Staff conducted observations of driver behavior on northbound Llama Street as vehicles approached Corintia Street for right or left turns. Field observations of 11 vehicles found that all four of the right-turning vehicles "stopped" (slowed to a speed less than 10 mph), and all seven of the left-turning vehicles "stopped" (slowed to a speed less than 10 mph) before turning onto Corintia Street. It is recommended that Llama Street be controlled with a STOP sign. In conjunction with installing the STOP sign, a yellow school crosswalk would be sttiped on Llama Street. RECOMMENDATION: The Traffic Safety Coordinating Committee recommends the installation of a STOP sign on Llama Street at its intersection with Corintia Street. NECESSARY CITY COUNCIL ACTION: The City Council must adopt an ordinance to establish the STOP sign as recommended. ( LOCATION MAP LEGEND: 0 PROPOSED STOP SIGN LOCA T/ON NOT TO SCALE PROJECT NAME EXHIBIT PROPOSED STOP SIGN 1 DRA'ttN BY: SCOTT EVANS, CARLSBAD ENGINEERING DEPT. 12/13/05 C: \ 1RAffiC\STOP SIGNS\STOP SIGN-LLAMA-CORINT1A1.DWG TITLE ( 155' REQUIRED 134' ACTUAL ---------7 REQUIRED LINE OF SIGHT 1-- I I I 50' I I lli ~ CJ') (MINOR) ~ STREET ::5 -.J (MAJOR STREET) CORINTIA STREET DECISION POINT 250' ACTUAL 155' REQUIRED (MAJOR STREET) CORJNTIA STREET ,--------- 1--lli ~ CJ') 50' 1 I I I I I I I ·~ ~ (MINOR) :J STREET DECISION POINT LLAMA STREET I CORINTIA STREET INTERSECT/ON APPROACH SIGHT TRIANGLE DRAl+N BY: SCOTT EVANS, CARLSBAD ENGINEERING DEPT. 12 IJ 05 C: TRAFFIC STOP SIGNS STOP S/GN-LLAMA-CORINTIA2.DWG EXHIBIT 2