MEMORANDUM TO: FROM: BY: TRAFFIC COMMISSION TERESA MCCLISH, COMMUNITY DEVELOPMENT DIRECTOR MATT HORN, CITY ENGINEER SUBJECT: CONSIDERATION OF RESTRICTING PARKING ADJACENT TO 170 AND 171 BRISCO ROAD DATE: RECOMMENDATION: It is recommended that the Commission advise the City Council to restrict parking adjacent to 170 and 171 Brisco Road. IMPACT ON FINANCIAL AND PERSONNEL RESOURCES: Staff time will be incurred, with a minor material cost of approximately $200, to perform parking restriction work. BACKGROUND: Previous Review On April 20, 2015 the Traffic Commission reviewed a request to restrict parking adjacent to the property located at 171 Brisco Road. The Traffic Commission reviewed this item and knowing that the property located at 170 Brisco Road has requested similar restrictions, continued this item in order to review the item holistically. Specifically the Traffic Commission directed staff to: 1. Expand notification area 2. Review stopping sight distance requirements from the Highway Design Manual (HDM) and the American Association of State Highway and Transportation Officials (AASHTO) 3. Complete sight triangle analysis for the properties located at 160, 166, 167, 170, 171, 174, 180, 182, 183, and 185 Brisco Road and have that information available for review. 4. Provide additional information concerning existing available on-street parking and how additional parking restrictions will impact on-street parking.
PAGE 2 170 and 171 Brisco Road 170 Brisco Road is a condominium complex with approximately 10 units and 22 on-site parking spaces adjacent to Oceano View Elementary School. 171 Brisco Road is a condominium complex with approximately 20 units and 36 on-site parking spaces. Brisco Road Brisco Road is an arterial roadway connecting US 101, West Branch Street, and El Camino Real to Grand Avenue. Brisco Road provides two-way traffic with one travel lane in each direction as well as parking on both sides of the roadway. The curb-to-curb width of Brisco Road is approximately 40 feet. The posted Speed Limit of Brisco Road is 35 MPH. The City received three requests to complete parking restrictions adjacent to the driveway entrances that serve 170 and 171 Brisco Road. ANALYSIS OF ISSUES: HMD vs AASHTO Stopping Sight Distance The HDM manual is prepared and published by Caltrans for use on the California State highway system. AASHTO, A Policy on Geometric Design of Highways and Streets was developed by a standing committee comprised of State Department of Highways, the Federal Highway Administration, and representatives of the American Public Works Association, the National Association of County Engineers, and the National League of Cities. The policy document is intended to be used both on local streets and highways.
PAGE 3 Sight distance is the length of the roadway ahead that is visible to the driver. The available sight distance on a roadway should be sufficiently long to enable a vehicle traveling at the posted speed limit to stop before reaching a stationary object in its path. This is known as stopping sight distance. Although greater lengths of visibility are desirable, stopping sight distance at every point along a roadway should be provided. Stopping sight distance is the sum of two distances: 1. The distance traversed by the vehicle from the instant the driver sights an object necessitating a stop to the instant the brakes are applied; and 2. The distance needed to stop the vehicle from the instant brake application begins. Below are stopping sight distance for a given posted speed limit from both the HDM and AASHTO guidance documents. HDM Stopping Sight Distance Values AASHTO Stopping Sight Distance Values Plotting the given stopping sight distance for the two documents yield:
PAGE 4 Tabulated Stopping Sight Distance Information Speed HDM AASHTO (MPH) (FT) (FT) (HDM-AASHTO) (HDM/AASHTO)% 15 100 80 20 125.00% 20 125 115 10 108.70% 25 150 155-5 96.77% 30 200 200 0 100.00% 35 250 250 0 100.00% 40 300 305-5 98.36% 45 360 360 0 100.00% 50 430 425 5 101.18% 55 500 495 5 101.01% 60 580 570 10 101.75% 65 660 645 15 102.33% 70 750 730 20 102.74% 75 840 820 20 102.44% 80 930 910 20 102.20% Average (all values) 103.03% Average (25 MPH to 45 MPH) 99.03%
PAGE 5 Reviewing all provided stopping sight distances from the two documents yields that the HDM average value is 103.03% of the stopping sight distance provided by AASHTO. When excluding the upper and lower ranges of stopping sight distances provided by the two documents and focusing on the range of values between 25 MPH and 45 MPH, which is the range of speed limits typically found in the City of Arroyo Grande, indicate the HDM average values is 99.03% of the stopping sight distance provided by AASHTO. Brisco Road has a variable longitudinal / centerline slope. The slope in the area of 170 and 171 Brisco Road is just under 9%. Using the HDM guidance from section 201.3: The stopping sight distances in Table 201.1 should be increased by 20 percent on sustained downgrades steeper than 3 percent and longer than one mile. Using HDM guidance, the stopping sight distance is not required to be adjusted for the analysis on Brisco Road. The AASHTO document also provides guidance when stopping sight distance for roads at grade may be disregarded: On nearly all roads and streets, the grade is traversed by traffic in both directions of travel, but the sight distance at any point on the highway generally is different in each direction, particularly on straight roads in rolling terrain. As a general rule, the sight distance available on downgrades is larger than on upgrades, more or less automatically providing the appropriate corrections for grade. This may explain why some designers do not adjust stopping sight distance because of grade. Exceptions are one-way roadways or streets, as on divided highways with independent profiles. For these separate roadways, adjustments for grade may be needed. For the purposes of Brisco Road analysis, both the HDM and AASHTO documents indicate that the stopping sight distance at 35 MPH is 250 feet, and indicate the grade of the road may be disregarded. The stopping sight distance of 250 feet is much more than what is currently provided and also might provide a more appropriate balance between both sight and parking needs. Sight Triangle In order to provide the necessary stopping sight distance, removal of portions of on street parking is required. Measuring line of sight distances and angles as shown below provides the necessary area of on street parking removal with s being equal to 250 feet. Overlaying this geometry on the subject driveways as well as other adjacent driveways provides the following results:
CONSIDERATION OF RESTRICTING PARKING ADJACENT TO 170 AND 171 BRISCO ROAD PAGE 6
PAGE 7 Using sight triangle analysis yields the removal of four parking spaces adjacent to 170 Brisco Road and four parking spaces adjacent to 171 Brisco Road for a total of eight onstreet parking spaces removed. Display showing parking removal adjacent to 170 and 171 Brisco Road Municipal Code While completing sight triangle analysis at each location of concern is the most accurate way to determine vision needs for a particular roadway speed as well as geometry, the Municipal Code provides minimum sight distances as well. 10.16.020 - Stopping and standing prohibited in certain places. It is unlawful for any person to stop, leave standing, permit to be stopped or permit to be left standing, any vehicle in the following places: A. Within fifteen (15) feet of an intersection; B. Within fifteen (15) feet of any fire hydrant; C. Within fifteen (15) feet of the driveway entrance to a fire station; D. Within fifteen (15) feet of the entrance to a hospital; E. On any reserved space, except to take on or let off passengers; F. In a crosswalk; G. On a sidewalk; H. In front of a public or private driveway;
PAGE 8 I. In an intersection, except along the opposing edge of a T-intersection where a prohibition is not needed for public safety and/or traffic control; J. On any city street, highway, or municipal parking lot where parking has been prohibited pursuant to Section 10.16.050 and where such street or parking lot is sign posted or painted with red paint on the curb surface; K. On any city street or highway where parking has been prohibited between designated time periods pursuant to Section 10.16.050 and where such restriction has been designated by appropriate signage and/or markers; and L. In any area reserved for preferential permit for residents, merchants and their guests under terms set forth in the resolution of the city council designating the geographic area, without possessing and displaying the proper city-issued permit. 10.12.020 - Vision triangle defined. For the purposes of this chapter, "vision triangle" is defined as follows: A. At street intersections, the boundaries of the vision triangle are formed by measuring along the curb lines from their projected intersection a distance of forty (40) feet and then connecting the two points with a straight line. B. At driveway entrances, the boundaries of the vision triangle are formed by measuring along the side of the paved driveway and along the street right-of-way line from their intersection a distance as specified below and then connecting the two points with a straight line: 1. Not less than ten (10) feet for local streets (less than sixty (60) foot right-of-way); 2. Not less than fifteen (15) feet for collector streets (sixty (60) foot or sixty-four (64) foot right-of-way); and 3. Not less than twenty (20) feet for major streets (as defined in the circulation element of the general plan. The Traffic Commission could determine that implementation of Municipal Code minimum might be the best course of action on a trial basis and reevaluate in the future if needed. This action would eliminate two parking spaces adjacent to 170 Brisco Road and one parking space adjacent to 171 Brisco Road for a total of three parking spaces. ALTERNATIVES: The following alternatives are provided for the Commission's consideration: Approve staff s recommendation; Provide alternate direction PUBLIC NOTICE AND COMMENT: This staff report was provided by US Mail to residences of 160, 166, 167, 170, 171, 174, 180, 182, 183, and 185 Brisco Road. The Agenda for this meeting was posted in front of City Hall on May 14, 2015 and on the City s website on May 15, 2015. Attachments: 1. Existing Parking Display