HomeMy WebLinkAbout102-1. Memo from Fehr & Peers.pdf
160 West Santa Clara Street, Suite 675, San Jose CA 95113 (408) 278-1700 Fax (408) 278-1717 www.fehrandpeers.com MEMORANDUM Date: February 23, 2010 To: John Cherbone, City of Saratoga,
Public Works Director From: Franziska Church/Sohrab Rashid Subject: Prospect Road/Scully Avenue Intersection-Sight Distance Evaluation 1025-446-1 Fehr & Peers has completed an evaluation
of sight distance at the Prospect Road/Scully Avenue intersection in Saratoga, California. A resident brought this item to the attention of the Saratoga Traffic Safety Commission (TSC)
at the January 13, 2011 meeting. The resident indicated that when vehicles park on the south side of the west leg of Prospect Road, they restrict visibility for vehicles turning left
out of Scully Avenue. After review of this issue, Fehr & Peers determined that looking to the west, parking should be restricted on Prospect Road for 40 feet west of Scully Avenue to
improve the sight distance to meet minimum sight distance requirements based on industry standards. standards. This memorandum summarizes the sight distance analysis at the Prospect
Road/Scully Avenue intersection. BACKGROUND Prospect Road is an east-west, four-lane major arterial that traverses the northern border of the City of Saratoga and connects Saratoga Avenue
and Stelling Road. The posted speed limit near the Scully Avenue intersection is 40 miles per hour (mph). Scully Avenue is a local street that connects Prospect Road to Larchmont Avenue,
where it terminates. The Prospect Road/Scully Avenue intersection is a full access, side-street stop-controlled intersection (i.e. Scully Avenue is stop-controlled). The Prospect Road/Scully
Avenue intersection is off-set from the Prospect Road/Larkin
A painted median island exists on Prospect Road between Clarkspur Lane and Scully Avenue (west of the Prospect Road/Scully Avenue intersection). A short, 150-foot
two-way left-turn lane exists on Prospect Road between Scully Avenue and Larkin Avenue to the east of Scully Avenue intersection. Bicycle lanes are striped along Prospect Road. On-street
parking is permitted on both sides of the Prospect Road/Scully Avenue intersection.. The two-way left-turn lane east of Scully Avenue provides westbound left-turn access from Prospect
Road for vehicles turning onto Scully Avenue. Additionally, there is an eastbound left-turn lane to provide U-turn access to the homes on the north side of Prospect Road for the approximately
700 feet between Clarkspur Lane and Scully Avenue. At the January TSC meeting, a resident pointed out that sight distance is limited for drivers in vehicles turning left from Scully
Avenue when vehicles are parked on the south side of the west leg of the Prospect Road/Scully Road intersection . Fehr & Peers conducted an evaluation to determine if the intersection
meets industry design standards, with and without vehicles parked on the south side of Prospect Road.
John Cherbone February 23, 2011 Page 2 of 4 SIGHT DISTANCE EVALUATION Sight distance is evaluated to determine if a driver will have adequate visibility to enter a roadway without resulting
in a conflict with traffic already on that roadway. In this case, adequate visibility should be provided so that a vehicle traveling northbound on Scully Avenue and turning left onto
Prospect Road will not conflict with through traffic traveling eastbound or westbound on Prospect Road. Additionally, a vehicle traveling eastbound or westbound on Prospect Road should
be able to see a vehicle exiting Scully Avenue so that adequate time is available for the driver to react and stop his or her vehicle, if needed. In accordance with Highway
Design Manual (HDM, 2007) the minimum stopping sight distance required for vehicles turning left from Scully Avenue to Prospect Road is 360 feet based on a design speed of 45 mph. Design
speed is typically five (5) mph hour higher than the posted limit, which is 40 mph on Prospect Road. During a field visit, the sight distance was measured at the northbound approach
of Scully Avenue approximately nine (9) feet behind the stop bar for both the eastbound and westbound directions. This distance from the stop bar is approximately where a driver would
be located when stopped and deciding when to turn. The available sight distance was measured to be at least 440 feet for vehicles traveling eastbound on Prospect Road (see Figure 1)
when no vehicles are parked on the south side of Prospect Road. With a vehicle parked on the south side of Prospect Road at the corner of the Scully Avenue intersection, the available
sight distance was measured to be 250 feet for vehicles traveling eastbound, as shown on Figure 2. Therefore, the existing sight distance when cars are parked on Prospect Road is less
than the minimum sight distance of 360 feet. Restricting parking for 40 feet from Scully Avenue (approximately two car lengths) will improve the sight distance to more than the required
360 feet. As shown on Figure 3, when no cars are parked on the south side of Prospect Road, the sight distance to the east was measured to be at least 580 feet as vehicles travel westbound
on Prospect Road. When a car is parked on the south side of Prospect Road, the sight distance to the east was measured to be approximately 330 feet (as shown in Figure 4) and is less
than the minimum sight distance of 360 feet. Restricting parking on the south-east side of the Prospect Road/Scully Avenue intersection for 40 feet from Scully Avenue (approximately
two car lengths) will improve the sight distance to more than the required 360 feet. CONCLUSIONS The 250-foot sight distance for drivers on Scully Avenue looking to the west on Prospect
Road when vehicles are parked on the south side of Prospect Road does not meet the minimum sight distance of 360 feet required by industry design standards. Restricting parking for 40
feet from Scully Avenue (approximately two car lengths) will improve the sight distance to more than the the required 360 feet.. Looking to the east, when vehicles are parked on the
south side of Prospect Road, the 330-foot sight distance does not meet minimum required sight distance. Restricting parking for 40 feet from Scully Avenue (approximately two car lengths)
will improve the sight distance to more than the required 360 feet.
John Cherbone February 23, 2011 Page 3 of 4 Figure 1: Prospect Road/Scully Avenue Intersection Looking West (towards Clarkspur Lane Avenue) from Scully Avenue with no parked vehicles
on the street Figure 2: Prospect Road/Scully Avenue Intersection Looking West (towards Clarkspur Lane Avenue) from Scully Avenue with parked vehicles on the street
John Cherbone February 23, 2011 Page 4 of 4 Figure 3: Prospect Road/Scully Avenue Intersection Looking East (towards Larkin Avenue) from Scully Avenue with no parked vehicles on the
street Figure 4: Prospect Road/Scully Avenue Intersection Looking East (towards Larkin Avenue) from Scully Avenue with parked vehicle on the street