Back-in Diagonal Parking with Bike Lanes
Prepared by Todd Boulanger, with contributions from Ali Goudarz Eghtedari and John Manix
McLoughlin Boulevard, a minor arterial in Vancouver, Washington, was no longer serving the surrounding land uses and users well. Along segments, the arterial was wider than its traffic volume necessitated, especially in the area of Clark College. The segments under study had one to two wide lanes in either direction and often no parking or parking limited to parallel stalls (see Image 1). The presence of on-street parking can positively or negatively affect the safety of bicyclists along the roadway. To provide new parking spaces while maintaining safety for bicyclists, Vancouver considered back-in diagonal parking. This design offers clear sightlines when pulling out and removes the risk that is present with parallel parking (a motorist opening the car door into the path of a bicyclist).
Image 1: Four lane configuration before back-in parking.
Diagonal parking in the city up to the point of this demonstration project was laid out conventionally to allow drivers to enter 45-degree stalls head-in along some of the wider arterials. Complaints about conventional diagonal parking focused on the restricted line of sight parkers had when leaving a stall and the insecurity of bicyclists in cycling along zones with conventional diagonal parking. Research conducted by the city in the 1970s documented the risk of vehicle-to-vehicle collisions when using head-in diagonal parking on an arterial street; to mitigate this concern, city engineers separated diagonal parking lanes from travel lanes with a 12-ft buffer lane for vehicle queuing (see Image 2).
The McLoughlin Boulevard corridor also lacked bike lanes, causing some bicyclists to ride on the sidewalk rather than on the street (Image 3). However, adding bicycle lanes to the head-in diagonal parking facilities with buffer zone presented a safety challenge.
In the proposed treatment section, McLoughlin Boulevard:
Image 2: Traditional diagonal parking with 12-foot buffer lane, no bike lanes and incomplete sidewalks (one block east of back-in zone).
- is a minor arterial,
- had two striped lanes in each direction and no parking,
- was identified as a facility with future bike lanes in the city's bike plan, and
- had an ADT of 6,800 in 2000.
In a zone to the east of the demonstration area, McLoughlin Boulevard has head-in diagonal parking with a 12-foot buffer lane (shown in Image 2).
This demonstration project had three objectives, which were to assess:
- Whether back-in diagonal parking would function as well as head-in diagonal parking with regard to safety and community acceptance.
- Whether back-in diagonal parking would allow bike lanes to replace vehicle buffer lanes for motorist maneuvering space, thereby improving bicyclist access.
- If the narrower street cross-section devoted to motor vehicle travel would lower the 85th percentile speeds.
Image 3: Bicyclist access before bike lanes.
Initial treatment sites along McLoughlin Boulevard were selected during a Neighborhood Traffic Management planning process in 1999-2000. The initial parking concept proposal languished until a facility plan for a public swimming pool proposed tearing down a heritage house for parking lot expansion in Hough. Community support for back-in diagonal parking grew because it would allow neighborhood associations to improve the surrounding parking supply while providing bicycle access to surrounding public facilities and protecting existing housing stock. The site of the demonstration was relocated one half-mile east of the original site, after a request by the Parks and Recreation Department for more parking for a second pool guaranteed funding for the striping demonstration project. Additionally, engineering staff considered the new site to be less politically risky for a long evaluation period, as it had a greater supply of off-street parking, which would allow drivers uncomfortable with back-in parking access to other parking options.
The demonstration project relied primarily on new bike lane striping, stenciling and signs to create back-in, diagonal parking stalls along a zone that did not have pre-existing parking. The pre-project lane configuration generally was four lanes with a striped center line for a 61-foot-wide street (shown in Image 1) classified as a minor arterial with 7,000 vehicles per day. The post-project lane configuration added separate lanes for parking and bike lanes while removing one lane in each travel direction (see Image 4 and Table 1).
Image 4: After conversiontwo-lane configuration with back-in parking on one side.
Support for the demonstration project was developed through repeated dialog with surrounding neighborhood associations and large institutional property owners, and then waiting for them to request project initiation at a later date. The bicycle community had guarded support for the project, as it provided one-half mile of additional bike lanes in an area with many residences and civic facilities (two swimming pools, a college, a high school, and a recreational center). Outreach to other stakeholders (elderly recreation facility clients, students, bicyclists, transit riders, pedestrians, and motorists) was accomplished by posting information on the city website; holding neighborhood newsletter discussions and a televised council session; and the posting of flyers on windshields, bus stops, and sidewalk A-boards along the project area. Final institutional support for the project was found after the transportation manager visited Seattle and observed back-in parking in use. The project then advanced to City Council for final, though guarded, approval.
Evaluation and Results
This demonstration project was evaluated using video analysis of motor vehicle interaction with parking (30 hours over six weekdays while college was in session), observational studies, feedback from users, review of collision rates and speed surveys, and review of citizen complaint files.
Image 5:Driver backing into stall.
- Some drivers had difficulty backing into spaces when few cars were parked versus when stalls surrounded by other parked cars, as there was less spatial reference.
- A few drivers preferred to pull into a back-in space by looping in through empty adjacent stalls versus stopping in the bike lane and backing up into a stalla behavior was not forecast before design.
- The six foot bicycle lane gave drivers adequate space for reversing into the parking stall with traffic.
Image 6: Easier unloading at the curb with back-in parking.
- Drivers that violated the bike lanes(drove through them without parking) and parking zones were typically leaving or entering the driveways nearest the parking zone versus drivers that were just driving through the zone.
- No drivers were observed violating the parking zone when cars were parked in it or when bicyclists were using the bicycle lane.
- Loading and unloading from parked vehicles was easier from the curb area (Image 6).
Image 7: Bicyclist's view along back-in parking zone.
- No bicycle-motorist conflicts were observed on the video footage, but there were too few examples to sufficiently judge this interaction between these street users.
- No vehicle-vehicle conflicts were observed on the video footage.
Bicycle Traffic Flows
- Bicycle traffic increased from one to six percent of all eastbound traffic along the project area, according to pre- and post-treatment tube counts taken from 10:00 am to 11:00 am during an average hour of use.
- Total bicycle traffic increased 235 percent from 17 bicycles to as many as 44 bicyclists after the bike lanes were added, according to tube counts and video analysis.
- Bikeway facilities provided more of a direct benefit than on-street parking facilities at this location, with 44 bicyclists versus eight parking drivers during the period with highest parking utilization based on video analysis.
- No recognized avoidance of back-in parking zone versus conventional parallel parking zone by either advanced or experienced bicyclists riding next to parked cars. Both zones had similar traffic flows.
Image 8. Exiting driver's view of approaching traffic along back-in parking zone.
Lane Configuration Effect on Speeds
The secondary objective of adding bike lanes and parking lanes was to reduce traffic speeds along the corridor. Vehicle speeds along this section of McLoughlin Boulevard were historically higher than the posted speed limit and neighborhood leaders, pedestrians, and bicyclists expressed concern about this problem during the Neighborhood Traffic Management planning process.
Post-project travel speeds were not reduced. They increased slightly (see Table 2). There is a visual break between the section west of the project area, which is a much more pedestrian-scaled, shared-use neighborhood. The project area, by contrast, is bordered by open-space land uses (sports fields) with few driveways and long blocks. In the next phase, enhanced pedestrian crossings with calming measures will be implemented.
- There were few collisions in both the pre- and post-time periods, so the project's influence on the collision rate along the parking zone is inconclusive. During 2000-2002, there were two collisions versus three collisions in 2002-2004.
- All except one of the collisions in both periods involved two vehicles, where one vehicle turning left into a driveway failed to yield to oncoming traffic.
- Both periods had one injury reported closest to the parking zone. The entire bike lane zone (which extends beyond the parking project area) had a total of six injuries before the addition of the bike lanes and one injury after.
- None of the reported collisions or injuries involved a bicyclist or driver undertaking a parking or exiting parking maneuver.
Conclusions and Recommendations
Based on the results of the analysis, the city decided to extend back-in angled parking with a bike lane to other segments of McLouglin Boulevard, as well as use back-in parking in other locations throughout Vancouver.
Recommendations for future Vancouver projects included the following:
- Widen the standard parking stalls from 9 feet to 9.5 feet or provide other stall position guidance such as raised markers.
- Adopt a supplemental back-in parking sign.
- Adjust the striping layout to add turn lane for west bound traffic into western entrance of parking lot (site specific).
Image 9: Simulation before back-in parking.
Overall, this treatment has been very effective at balancing bicyclist access (an increase in trips) while providing for growing parking demand. The adoption of recommendations #1 and #2 has met resistance from city maintenance crews ("another sign to stock" and "if the drivers need the pavement markers, then there must be a problem with this type of parking"). The proposed projects will be using the wider stall (9.5 feet).
The use of photo simulations of the planned parking scenario was very helpful during the staff and public process stages, as few if any stakeholders had experienced this type of parking before or remembered doing so while visiting Seattle in the past (Images 9 and 10). This type of parking demanded a lot of public discussion, more so than any other striping project, especially since parking was being added rather than removed. It is ideal for a stakeholder group (business, engineers, residents, etc.) to visit a city with this type of parking before adopting it on a district-wide basis.
Image 10: Simulation after back-in parking.
Vancouver plans to adopt the back-in form of diagonal parking along wider arterials where bike lanes are desirable and the surrounding land uses support pedestrian trips and shared uses. The use of conventional diagonal parking with bike lanes is no longer acceptable. Where bike lanes are required and back-in parking is not adopted because of low resident and business support, parallel parking is indicated. Back-in parking with bike lanes might be thought of as a kind of road diet, plus having parking and bike lanes but still keeping a narrower cross section to constrain car traffic.
Costs and Funding
An original budget of $5,520 for signs, striping and traffic control was established. This cost was split between the Transportation Services and the Parks and Recreation departments (the parking was located in front of their recreation facilities and at their request). At the time of the project, the City was in the process of applying for Community Development Block Grant federal funds for the second portion of $100,000 to fund pedestrian crossings. These funds were added to $80,000 allocated for the striping and refuge islands.
Ali Eghtedari, PE
Traffic Engineering & Operations
City of Vancouver