Back in 2009, Hennepin Avenue in downtown Minneapolis was converted from a one-way to a two-way street. Bicycle facilities along the corridor changed from a center two-way bicycle lane to designated shared lanes for bicyclists, buses, and right turning motor vehicles. Responding to initial concerns over the visibility of the bicycle lane markings, the city turned to painting it green. They received special permission for the experiment from the Federal Highway Administration (FHWA), complete with the need for an evaluation report[1]. Post conversion, most bicyclists used the facilities in ways intended, but only when drivers were not blocking or encroaching on the lane[2]. Simon Blenski tells me the biggest challenge for this ‘paint only’ treatment was too much traffic[3]. The volume of motor vehicles was incompatible with shared lane markings. Streets with high volumes of vehicular traffic, it was decided, deserve a dedicated space for bicycles. It was a job asking too much of a paint-only treatment. Meanwhile, sometimes only in high trafficked areas, green paint is used extensively in New York City. In fact New York’s application is only used for mid-block treatments (only in non-conflict zones)[4]. The primary motivation, as I understand it, is that green in the intersections might spur cyclists to let down their safety guard.

The first post in this series alerted us to some of the problems using colored paint; the second told us why using paint can be advantageous. Here I rationalize and prescribe guidelines for its sparring use.

Countries, states (regions) and even cities have their own guidelines for using paint. National guides in the U.S.–FHWA efforts—include the Bicycle Facilities Guide from the influential American Association of State Highway Transportation Officials (AASHTO) (covering standards such as bike lane width), and the Manual on Uniform Traffic Control Devices (MUTCD) (covering signs, signals, and pavement markings). But these are only guidelines, and each state has their own version. MUTCD does authorize experiments. They grant interim approvals for some uses. But MUTCD is slow to make them official and they are usually conservative in scope. Work from NACTO is helping push the envelope with respect to innovation, complete with a step towards standardization. This is an initiative that has, in part, been adopted by the relatively new Green Lane Project[5].

Both NACTO and FHWA are working to clarify how colored paint should be used in the form of design recommendations. They agreed that green is the preferred color in the U.S.[6]. But lacking more precise guidelines, cities are rightfully doing a lot of experimenting with how to use it. This leaves most transport planners (at least in the U.S.) longing for both: (a) better instructions for how to use paint, and (b) formal endorsement of the NACTO guide from FHWA[7]. More precise guidelines might be on line as early as September but in general, this is an active area that will likely see focused development over the next two years. Here are some guidelines for which the future “guidelines” should focus.

Minneapolis currently employs green paint to enhance: (a) bike lanes at intersection conflict points, (b) bike (and turn boxes), (c) crosswalks and shared lane markings, and (d) the start of a protected bike lane. Seattle’s applications are strikingly similar[10]. Combined, these lists provide a good starting point. Colored paint works best where roadway space is clearly shared between modes. Its use broadly divides into three categories:

(1) Conflict areas: paint should be use to highlight difficult conflict areas between cyclists and motorists through junction areas. More than four out of five bicycle crashes in Minneapolis occur at intersections (and merge zones)[11]—areas that warrant highlighting from users. Such instances include but are certainly not limited to, the right hook, standard crossings, areas where facilities cut across an auto on-ramp, intersections with protected bike lanes, and other areas where separate bicycle facilities cross roadways  (or vice versa). Municipal resources would dictate how many conflict points can be addressed.

(2) Something special: paint should be used to indicate an exceptional treatment for bicycle facilities—either forthcoming in the travel or a place for refuge. These could include the start (or end) of a protected lane, a left turn waiting areas or a bike box, for instance.

(3) Aggressive experiments: in the forthcoming evolution of how street space will change in cities, paint is the transport planner’s friend. As mentioned in Part 2 of the series, paint should be applied more liberally when cities are trying something avant-garde. It can be used more aggressively to signal notable experiments where roads are being repurposed. The new or experimental nature demands more attention. Once it is no longer new (after a year or if it is deemed not to work) then it could conceivably be erased or left to pasture.

Guidelines should also specify where paint should not be used. Clearly separated bicycling facilities fall into this category. Paint should not be used to indicate bicycle travel corridors adjacent to high vehicular traffic volumes (cyclists require separate facilities). Mid-block treatments usually fall into this category. It is too confusing to motorists and cyclists alike. This suggests that painting an entire cycling system—while helpful to highlight initial impact—might be overkill and presents headaches for maintenance. I realize this might be heresy, especially compared to the extensive colored networks used in the Netherlands[12]. But the Dutch embed their redish color with the mixing of the asphalt and use it primarily for completely separated facilities. Streets in the U.S. will be adapting over the next few years—changes that are well suited to paint.

Paint is a critical ally as cities aim to spur more innovative bicycle facilities with less. Here’s to unified and clear guidance for applying this valuable resource[13].