CITY OF LARKSPUR, CALIFORNIA
GENERAL PLAN

CHAPTER 4, CIRCULATION

CONTENTS
  • Chapter 4, Circulation
  • Roadway Circulation
        How Congested are the Roads?
        The Level of Service Concept
             Signalized Intersections
             Unsignalized Intersections (Minor Street Stop
             Unsignalized Intersections (All-Way Stop)
        Key Corridors
             Highway 101
             Sir Francis Drake Boulevard
             Magnolia Avenue
             Doherty Drive
             Wolfe Grade
             Bon Air Road
             Madrone Avenue
             Redwood Highway
        Traffic Accident Patterns
        Projected Future Conditions
        Model Method and Assumptions
        Effect of Growth on Level of Service
             Sir Francis Drake Boulevard Corridor
             Magnolia Avenue Corridor
             Doherty Drive Corridor
        Systemwide Considerations
        Ridesharing
        Parking
             Downtown
             North Magnolia
             New Developments
             Residential Areas
             Future Issues
  • Transit
        Local Bus Service
        Commute and Basic Bus Service
        Ferry Feeder and Ferry Service
        Para-transit Service
        Airporter Feeder Service
        Taxi Service
        Park-and-Ride
  • Regional Considerations
        Marin County General Plan
        Sir Francis Drake Signal Interconnection
        Use of the NWP Rail Right-of-Way East of Highway101
        Highway 101 Interchanges
        Cal Park Hill Auxiliary Lane
        Highway 101 High Occupancy Vehicle (HOV) Lanes
        Local Growth
  • Circulation Goals, Policies and Program
        Quality of Life
        Transportation Alternatives
        Internal and External Circulation Linkages
        Freeway Access
        Travel To and Between Retail Areas
        Downtown Circulation
        Safety
        Circulation and Environmental Protection
             Implementing Circulation Improvements
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Chapter 4. Circulation

This chapter describes the existing circulation system and travel characteristics in and around the City of Larkspur. It also projects future demand for travel, based on "build-out" of the Land Use Plan and the anticipated circulation deficiencies that would result, and suggests potential ways to alleviate these inadequacies. At the conclusion, these technical analyses are brought together with practical community needs and desires, and presented as the Circulation Goals, Policies, and Programs.

Figure 4-1 (next page) shows Larkspur's relationship to the regional circulation system. Circulation in the city and its Sphere of Influence (which includes the unincorporated areas of Greenbrae and Kentfield) is heavily influenced by its location at the junction of U.S. Highway 101 (the north-south spine of eastern Marin County) and Sir Francis Drake Boulevard, the only east-west roadway that completely spans the county. As a result, the city is traversed by many "through" travelers.

Travelers move about Larkspur in a number of ways: roadways, fixed route local and commuter bus transit, airport feeder service (to San Francisco International), ferry service, para-transit, taxi, and bicycle, pedestrian, and equestrian paths. The 1980 census provides some insight into how Larkspur's citizens travel to work. Although home-to-work trips are only one element of the traffic flow, they make up a large portion of peak hour traffic the time when most congestion occurs (see Figure 4-2). Most Larkspur citizens either drive to work alone (58 percent) or share a ride (15.6 percent), for a total of almost three-quarters of commuters. Close to 17 percent took transit, and the remaining 10 percent used others methods, such as walking, bicycling, or motorcycling, or stayed at home.

It is also interesting to see where people work (see Figure 4-3). Almost equal numbers of people work in Marin County (46.6 percent ) and San Francisco (46.3 percent ). About 12 percent live and work in Larkspur. Smaller percentages work in other counties in the Bay Area.

Figure 4-1
Regional Location Map
Figure 4-1

Figure 4-2
Mode of Travel To and From Work,
Larkspur Residents, 1980 Census

[to be inserted]

Figure 4-3
Location of Work Place,
Larkspur Residents, 1980 Census

[to be inserted]

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ROADWAY CIRCULATION
Larkspur is served by three main traffic arterials which carry both local and through traffic (see Figure 4-4):

  • Sir Francis Drake Boulevard;
  • Corte Madera Avenue, Magnolia Avenue, and College Avenue; and
  • Doherty Drive.

In addition, Highway 101 provides regional access. Other roads also serve important circulation functions in Larkspur:

  • Bon Air Road, which connects Sir Francis Drake Boulevard to Magnolia Avenue.
  • Wolfe Grade, which provides access to D street in San Rafael from Sir Francis Drake Boulevard.
  • Madrone Avenue, a collector serving the area west of Magnolia, south of Downtown.
  • Redwood Highway, which parallels Highway 101 in the vicinity of the Lucky Drive/ Industrial Way interchange.

Other roadways in Larkspur provide local access to property. Although these are important, the main focus of the General Plan is on roads of city-wide significance.

Circulation options in the Larkspur area are relatively constrained. First, there are only the three through-corridors described above. Virtually all trips made in Larkspur travel on one or more of these roads. Second, there are only three crossings of Corte Madera Creek: one at College Avenue, another at Bon Air Road, and the third at Highway 101. Quite a bit of local travel uses the freeway just to get over Corte Madera Creek.

How Congested Are the Roads?
Traffic flow in urban settings is usually constrained by the manner in which traffic passes through intersections. Other factors that can reduce the ability of a roadway to handle traffic flow relate to frequency of driveway access, width of the roadway, and grade. Considering these characteristics of urban traffic flow, a measurement technique known as "Level of Service" is used by transportation engineers to compare conditions.

The Level of Service Concept
The Level of Service analysis results in a letter grade for each intersection studied, from A through F, with A being free flow with insignificant delays, to F, which is a gridlock condition. As part of its Circulation Assessment Permit (CAP) ordinance, the City of Larkspur has implemented a policy that intersections should not be worse than Level of Service (LOS) D during peak periods. However, some intersections on Sir Francis Drake Boulevard are operating at LOS E during peak periods.

Different techniques are used to evaluate Level of Service depending on the type of control at the intersection.

Figure 4-4
Primary Circulation System, Larkspur
Figure 4-4



Figure 4-5
Level of Service Definitions, Signalized Intersections

Level of
Service
Vehicle
Delay
Seconds
Volume to
Capacity
Ratio
Description
A <5.00 0.00-0.59 Free Flow, Insignificant Delays: No approach phase is fully utilized by traffic and no vehicle waits longer than one red indication.
B 5.1-15.0 0.60-0.69 Stable Operation, Minimal Delays: An occasional approach phase is fully utilized. Many drivers begin to feel somewhat restricted within platoons of vehicles.
C 15.1-25.0 0.70-0.79 Stable Operation, Acceptable Delays: Major approach phases fully utilized. Most drivers feel somewhat restricted.
D 25.1-40.0 0.80-0.89 Approaching Unstable, Tolerable Delays:Drivers may have to wait through more than one red signal indication. Queues may develop but dissipate rapidly, without excessive delays.
E 40.1-60.0 0.90-0.99 Unstable Operation, Significant Delays:Volumes at or near capacity. Vehicles may wait through several signal cycles. Long queues form upstream from intersection.
F >60.0 N/A Forced Flow, Excessive Delays: Represents jammed conditions. Intersection operates below capacity with low volumes. Queues may block upstream intersections.

Source: Highway Capacity Manual, Special Report No. 209, Transportation Research Board, Washington, D.C., 1985.

Figure 4-6
Level of Service Definitions, Unsignalized Intersections

Level of Service Expected Delay Reserve Capacity
(Vehicles/Hour)
A Little or no delay <400
B Short traffic delay 300-399
C Average traffic delays 200-299
D Long traffic delays 100-199
E Very long traffic delays 0-99
F Extreme delays potentially affecting
other traffic movements in the intersection
<0
Source: Highway Capacity Manual, Special Report No. 209, Transportation Research Board, Washington, D.C., 1985.

  • Signalized Intersections. At signalized intersections, an overall relationship of the volume using the intersection to its capacity is translated into the Level of Service grade. Figure 4-5 (preceding page) provides definitions of each of the Level of Service grades, and their corresponding volume-to-capacity (V/C) ratio. The Level of Service D threshold is represented by a V/C ratio of between 0.80 and 0.89.

  • Unsignalized Intersections (Minor Street Stop). For unsignalized intersections where stop control is provided on the minor street only (e.g., Magnolia Avenue intersection with William Avenue), each traffic movement that must yield to another movement is given a letter grade, based on the availability of gaps in the conflicting traffic flow to make the turn. Usually, the left-turning traffic from the minor street (e.g., William Avenue) onto the major street (e.g., Magnolia Avenue) has the worst Level of Service. Figure 4-6 on the preceding page summarizes the Level of Service definitions for two-way stop-controlled intersections. It should be noted that this type of intersection may generally operate with little delay, but left-turning traffic from the minor street could have difficulty finding a gap in the traffic flow on the major street, resulting in an "F" grade.

  • Unsignalized Intersections (All-way Stop). For unsignalized intersections with all-way stop control (e.g., Magnolia Avenue at King Street), an overall Level of Service indication for the intersection is possible, based on the relationship of volume to overall capacity. However, it is only possible to determine whether the intersection is better or worse than LOS C.

Note that it is not appropriate or possible to directly compare the Level of Service grade of one type of intersection (e.g., signalized) with another type (e.g., unsignalized).

Key Corridors
The following describes each key corridor in the city, its overall traffic flow characteristics under existing conditions, and as appropriate, Level of Service ratings at critical locations. Two illustrations have been prepared to highlight traffic conditions in Larkspur. Figure 4-7 shows estimated average daily traffic volumes at selected key locations on the city's circulation system. Figure 4-8 illustrates locations where the Level of Service is approaching, at, or over the threshold of D ordained by the city.

Figure 4-7
Average Daily Traffic, Existing Conditions, 1989
Figure 4-7




Figure 4-8
Existing Level of Service Deficiencies, 1989
Figure 4-8

SOURCE:
Robert L. Harrison, City of Larkspur
Traffic Mitigation Fee Program,
Final Project, November 1988
Note: Service Level is not shown for intersections operating at LOS C or better.

Highway 101. Route 101 is usually quite congested in the vicinity of the Sir Francis Drake Boulevard interchange (also called the Greenbrae interchange), especially north of the interchange going up Cal Park Hill. Traffic from the northbound Sir Francis Drake Boulevard on-ramp merging onto the freeway exacerbates the capacity-reducing impact of the upgrade. In the southbound direction, there are conflicts between traffic entering the freeway and cars exiting at Lucky Drive. At the Lucky Drive interchange, the southbound on- and off-ramps meet Fifer Avenue and Nellen Avenue at the ramp terminus, resulting in difficulty for through-traffic on Nellen. Recent Caltrans studies indicate that there is little excess capacity on the freeway on the Greenbrae interchange ramps as they are currently configured. The 1987 volume south of the interchange was estimated by Caltrans to be 160,000 vehicles per day; north of the interchange Caltrans estimates 135,000 vehicles per day.

Sir Francis Drake Boulevard. This is a key east-west through-road in Marin County, stretching from Point Reyes on the west to the San Quentin Peninsula on the east. In the Larkspur Sphere of Influence, it begins on the west at the boundary with Kentfield as a four-lane, undivided roadway with some twists and turns, but becomes divided on the approach to College Avenue. In the commercial area east of College Avenue near the College of Marin, limited on-street parking is allowed. Further east, Sir Francis Drake passes the Bon Air Shopping Center, where significant turning traffic tends to cause delays in through-traffic flow.

As the road approaches the Greenbrae interchange, only the left lane continues through to East Sir Francis Drake Boulevard - the right lane becomes the southbound Route 101 on-ramp. For westbound traffic near the interchange, only one lane serves through-traffic, while two left-turn lanes lead to the southbound on-ramp. The interchange itself is an intricate assembly of ramps that separates conflicting traffic flows, with some non-standard characteristics. For example, traffic desiring to proceed northbound on Route 101 from the Redwood Highway on ramp just south of the Greenbrae interchange must first cross Sir Francis Drake Boulevard at grade. This additional traffic tends to degrade the Level of Service at this intersection to the D level currently experienced.

Just east of the interchange, East Sir Francis Drake Boulevard has two through lanes in each direction and a median as it passes the Golden Gate Transit Ferry Terminal and the Larkspur Landing mixed use development. East of Larkspur Landing, Drake becomes a two-lane undivided roadway with refuge for left-turning traffic. It continues past the State prison and intersects with Andersen Boulevard in San Rafael, then leads directly onto the I-580 eastbound on-ramp and the Richmond-San Rafael Bridge.

On Sir Francis Drake Boulevard, morning traffic flow is heavy, but not gridlocked. The area in front of the Bon Air Shopping Center (near Eliseo Drive), tends to experience some back-ups. In the evening, the situation is much worse, with long back-ups from Wolfe Grade eastward to the freeway. On the east side of the Greenbrae interchange, traffic also backs up through the old railroad trestle from a combination of traffic from the Golden Gate Transit Ferry Terminal, Larkspur Landing, and traffic heading from the Richmond-San Rafael Bridge towards Route 101 southbound. Average daily traffic volumes in 1988 on this road ranged from about 20,000 at the eastern city limit to about 52,000 just east of Eliseo Drive.

In particular, the intersections of Sir Francis Drake Boulevard with La Cuesta Drive and Eliseo Drive are either approaching or at capacity (LOS F - see Figure 4-8). Other locations of concern are unsignalized intersections where turning traffic from the minor street has difficulty finding a gap - Larkspur Landing Circle (east), Andersen Drive, and El Portal.

Magnolia Avenue. Magnolia Avenue begins north of the City of Corte Madera, at the intersection of Branch Avenue. South of this intersection, this non-freeway north-south corridor parallels Route 101, taking the name Corte Madera Avenue, Camino Alto, and Miller Avenue. For travelers to and from Larkspur, the combination of Magnolia Avenue and Redwood Avenue/ Tamalpais Drive (in Corte Madera) provides convenient access to Route 101.

Northbound Magnolia Avenue first passes through the older Downtown area where it is a two-lane, slow moving facility with many driveways and intersections (most of which are stop-sign controlled) and on-street parking. Intersections in this area are tightly spaced (sometimes less than 200 feet apart), and left-turn pockets are not provided. There are also numerous pedestrian crossings, especially in the Old Downtown. These conditions combine to create congestion, where it is often difficult for pedestrians to cross, and where turning vehicles cause long queues because they do not have the protection of a turn lane. The Average Daily Traffic (ADT) on Magnolia Avenue in the vicinity of King Street was about 12,000 in 1988, a heavy volume for a constricted two-lane roadway.

North and west of Doherty Drive, Magnolia Avenue becomes more free-flowing, with fewer intersections and driveways. Further along, Magnolia Avenue runs through another commercial area, also with on-street parking, although the roadway is somewhat wider than in the Downtown area, and congestion is less. At the city limit, Magnolia Avenue becomes College Avenue, where it passes the College of Marin to end at Sir Francis Drake Boulevard. The ADT at this northern terminus was about 14,500 in 1988.

Only the Corte Madera Avenue/Redwood Avenue intersection (not in the city or its Sphere of Influence) is rated in the unacceptable range (LOS F, see Figure 4-8, page 63). However, traffic conditions through Downtown Larkspur are cause for concern because of restricted room to maneuver, sight-distance problems, and the pedestrian/auto interface. In response to these problems and recent accidents, the City changed the traffic control at the Magnolia Avenue/King Street intersection (adjacent to City Hall) to all-way stop control. (Previously Magnolia Avenue traffic did not have to stop.) This configuration tends to cause congestion at this location, with queues sometimes extending to adjacent intersections. However, it is easier for pedestrians to cross Magnolia Avenue. Many times each year, Magnolia Avenue is gridlocked when traffic diverts from Highway 101 because of an accident.

Doherty Drive. This corridor provides both local access for community facilities (e.g., Piper Park, Redwood High School, Henry C. Hall School, the Twin Cities Police Department) and several residential neighborhoods, and also serves as a through facility between Larkspur and Highway 101. The eastern portion of this through corridor passes through the neighboring city of Corte Madera, via Lucky Drive, Fifer Avenue, and Nellen Avenue. The ADT in the Larkspur portion of this corridor at Larkspur Plaza was about 8,800 in 1988.

At its western terminus, Doherty Drive is a wide, two-lane facility, with pedestrian crossings near the Hall School (at Larkspur Plaza Drive, and at Larkspur Boardwalk). Further east is another pedestrian crossing at Riviera Circle, serving the high school. This intersection also has four-way stop signs to provide the necessary control for pedestrians to cross safely. Just east of Riviera Circle is the Corte Madera city limit beyond which travelers to the freeway must turn left onto Lucky Drive. An additional turn onto Fifer Avenue is required for freeway traffic. There, southbound traffic can enter the freeway ramp directly, while northbound traffic must use Nellen Avenue to circle under the freeway to Redwood Highway, where the Industrial Way ramp is used.

Traffic generally flows reasonably well along this corridor, despite the twists and turns and stop sign controls. The heaviest flow occurs between 7:30 and 8:00 AM and between 3:00 and 3:30 PM, related to the start and end of the school day. Two intersections operate at LOS F, Fifer Avenue at Nellen Avenue (in Corte Madera), and Industrial Way at Redwood Highway (at the northbound freeway ramps). Both of these intersections are unsignalized.

Wolfe Grade. Wolfe Grade is a two-lane, undivided, winding, hilly road that connects Sir Francis Drake Boulevard to downtown San Rafael at D Street. It had a 1988 ADT of 13,700, and is often used, in conjunction with Sir Francis Drake Boulevard, to bypass Highway 101 when the freeway is congested.

Bon Air Road. Bon Air Road is a two-lane divided roadway where it passes Marin General Hospital. Just north of the hospital, it becomes a four-lane divided road. It serves mainly to connect Sir Francis Drake Boulevard with Magnolia Avenue, and provides access to Marin General Hospital and the residential neighborhood on Bon Air Hill.

Madrone Avenue. This road is narrow and winding, and serves many homes west of Magnolia Avenue. Portions of the road are paved around old redwood trees.

Redwood Highway. This road parallels Highway 101 on the east side, serving as part of the Doherty/Lucky/Fifer/Nellen/Redwood freeway access. It also serves the industrial land use, trailer park, and Greenbrae Boardwalk, east of Highway 101.

Traffic Accident Patterns
A summary of accident frequency for the five year period between 1984 and 1988 was obtained from the Twin Cities Police Department. Figure 4-9 shows the total number of traffic accidents reported at locations on the primary street system where generally more than one accident occurred per year. Locations in bold are those that exceed the average number of accidents at all locations.

While this is not a definitive accident study, it does indicate the relative level of accidents at key locations in the city. The highest number of accidents over the five-year period occurred at the intersection of Sir Francis Drake Boulevard with the Route 101 northbound ramps (78 accidents, compared to an average of 22 per intersection). At this intersection, the high traffic volumes, combined with confusing geometrics and narrow channels under the railroad trestle, create hazardous conditions.

Figure 4-9
Accident Summary, City of Larkspur, 1984-1988

Intersection Total
  
Magnolia at:
Piedmont 11
Baltimore 7
Madrone 17
King 27
Cane 21
Ward 32
Doherty 31
Bon Air 28
Dartmouth 21
Frances 9
Estelle 8
Murray 12
  
Sir Francis Drake at:
El Portal 10
Eliseo 19
NB 101 Ramps 78
Larkspur Landing Circle (W) 11
Larkspur Landing Circle (E) 57
  
Doherty at:
Larkspur Plaza 19
Redwood High School 7
Riviera Circle 8
  
Bon Air at:
South Eliseo 15
  
Intersection Average 22.4