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Michael Sallaberry, PE, Associate Transportation Engineer, San Francisco Department of Parking and Traffic
The Embarcadero is a waterfront arterial in San Francisco that replaced a freeway heavily damaged by the Loma Prieta Earthquake of 1989. The roadway varies from four to six lanes (two to three in each direction) and now handles weekday traffic volumes of 40,000–50,000 vehicles per day.
After the roadway was constructed and while the area along the waterfront continued its evolution, it was determined in some areas that there was a need for on-street parking during non-peak traffic periods. During peak periods, there would be a tow-away restriction to uncover a third travel lane in each direction. While the accommodation of bicyclists was intended along the length of the roadway, there was a problem with how to stripe or designate space for cyclists to use along the sections with part-time parking.
One option was to stripe two rows of shared lane markings along each direction of the roadway, one along the curb to show where cyclists would ride when there was no parking allowed and the other farther away from the curb when parking was allowed. This was rejected on the basis that two rows of bicycle specific markings would be confusing to road users. Also, it generally is desirable to explore options which give cyclists their own striped space on the roadway before accepting shared lane markings in narrow lanes.
Figure 1. Cyclist using space between parked cars and first lane.
Figure 2. Northbound Embarcadero floating bike lane during tow-away.
Figure 3. Cross-hatching at beginning of part-time bike-parking lane, northbound Embarcadero.
Figure 4. Merge sign, southbound Embarcadero at beginning of part-time bike-parking lane.
To give cyclists a designated space along the section of roadway with part-time parking, the design shown in figures 1 and 2 was chosen. When parking is allowed, cyclists use the space between the parked cars and the solid 10.2 cm (4 in)–wide white stripe, a space about 2.1 m (7 ft) wide depending how close cars park to the curb. When parking is not allowed, as shown in Figure 2, cyclists move to the right and use the 1.5 m (5 ft)–wide shoulder. Motorists are able to use the third lane, which at 3 m (10 ft) wide is narrow, but wide enough to accommodate the generally slower traffic speeds one would expect during peak hours.
Before this design, there was some trial and error along the way. The 10.2 cm (4 in) solid white line shown 4.5 m (15 ft) from the curb in Figure 1 initially was farther out at 4.7 m (15 ft, 6 in) and broken, like a typical lane line. While this allowed for a 3.2 m (10 ft 6 in) motor vehicle lane when no parking was allowed, it also created a wider space alongside the parked cars when parking was allowed. The space looked like a typical travel lane but actually was too narrow to accommodate traffic. The result was that motorists used the space and sideswiped parked cars, filling the space intended for cyclists.
To make the space between the first 10.2 cm (4 in)–wide lane line and the parked cars seem less like a travel lane to motorists when parking is allowed, the 10.2 cm (4 in)–wide white line was moved closer to the curb face. It was also made solid to discourage crossing and make the lane seem less like a travel lane. The parking T’s, initially 2.1 m (7 ft) from the curb, were relocated to be 2.4 m (8 ft) from the curb and painted with longer stems. The placement was meant to further narrow the space by encouraging people to park their cars farther from the curb while the longer stems were to make the space seem less like a travel lane. And finally, cross hatching was added in the 3 m (10 ft) space at the beginning of the floating bike lane sections to further discourage motorists from using the space when parking was allowed (see figure 3). While this was meant to make the space narrower and less attractive to motorists when parking is allowed, it still remains wide and attractive to cyclists.
Would these efforts to make the space less attractive to motorists when parking was allowed result in the space not being used by motorists when parking was restricted and they were expected to drive in the third lane? From observations, motorists use the 3 m (10 ft)–wide third lane as intended when parking is not allowed. The theory is that while it does not look like a conventional lane, motorists, especially when traffic congestion reaches certain levels (such as during peak hours), will use whatever reasonable space is available to them. An analogy is that the design works as a pressure release valve with the unusual-looking third lane used only when traffic levels reach a certain level.
Use of signs associated with this unusual arrangement has been minimal. While it was tempting to place signs along these stretches to explain what is going on, initial sign designs were too complicated or incomplete. Though signs always were an option if the roadway lane markings were not sufficient, it was determined that signs explaining the part-time use of the space were not necessary. The only signs pertinent to the design are the tow-away signs (circled in Figure 1) and the merge sign used in the southbound direction (figure 4). There, three full-time lanes enter the section with the floating bike lane, and the three lanes narrow to two travel lanes when parking is allowed. Bike route signs are also along this area.
There have been some calls to install bicycle markings on the street. But as mentioned earlier, two sets of markings would be necessary for cyclists as they shift from one space to another, resulting in a confusing arrangement. Cyclists tend to stay to the right, so when there is no parking allowed, they naturally ride in the 1.5 m (5 ft)-wide shoulder. When parking is allowed, they ride in the space between the parking and the 10.2 cm (4 in) solid white stripe.
While there has not been a quantitative evaluation of the design, observations indicate the space is now working as intended. Feedback from cyclists, motorists, and employees of the Port of San Francisco along the Embarcadero has been utilized throughout the process. Initial feedback and observations yielded the modifications to the design, while the good feedback and lack of negative feedback have reflected observations that the design essentially works. The primary comment heard now is that there should be pavement markings for cyclists, but the potential confusion caused by trying to mark a shifting space would likely outweigh any benefits.
The design result of this trial and error process to accommodate cyclists along a roadway with part-time parking is shown in Figures 1 and 2. If this approach of creating shifting bike lanes is used, the key is to not make the space between the parked cars and the first 10.2 cm (4 in) lane line too wide. With the 10.2 cm (4 in) lane line initially 4.7 m (15 ft 6 in) from the curb, the space was wide enough to attract motorists when parking was allowed. This 4.7 m (15 ft 6 in) width resulted in sideswipes with parked vehicles and motorists in the space intended for cyclists. Another key is to ensure that traffic levels are reasonably accommodated when parking is allowed so that there is less temptation to try to use the space intended for cyclists.
Based on observations, generally good feedback from cyclists and lack of significant negative feedback, the current design is considered effective. While not perfect, with its slightly confusing, unorthodox design, it successfully accommodates cyclists, part-time on-street parking, and motorists needing additional capacity during peak hours. It does so with minimal signs, leading one to conclude that while the design is unorthodox, it uses fairly predictable road-user behavior to its advantage. Cyclists naturally tend to stay to the right, and motorists will use a space even if it is not clearly for their use if traffic congestion reaches certain levels and the space is reasonably accommodating.
Costs of the final design are typical of basic striping and signage projects. However, the amount of re-striping and trial and error did add to the final cost. Costs were not tracked.
Michael Sallaberry
San Francisco Department of Parking and Traffic
(415) 554-2351
mike.sallaberry@sfgov.org