Requiring Motorists to Merge into Bike Lanes Prior to Right Turns


Source: VeloTraffic

Right Hook Crash Type (via

One of the most common crashes that occurs involving bicyclists on urban streets is the “right-hook”, or the crash that occurs when a right-turning motorist fails to yield to a through bicyclist traveling the same direction in a bicycle lane.

Engineers, Cyclists, and Lawmakers alike have long known that this configuration of right-turning motorists positioned to the left of through bicyclists is problematic, and there are a number of regulations and design standards in place to prevent or mitigate these challenges.

For example, current state law requires motorists to merge into the bicycle lane prior to executing a turning movement. Minnesota Statute 169.19 Subd. 1 says the following (emphasis mine):

(g) Whenever it is necessary for the driver of a motor vehicle to cross a bicycle lane adjacent to the driver’s lane of travel to make a turn, the driver shall drive the motor vehicle into the bicycle lane prior to making the turn, and shall make the turn, yielding the right-of-way to any vehicles approaching so close thereto as to constitute an immediate hazard.

There are also design standards in place that are intended to communicate these regulations to motorists and bicyclists. The AASHTO Guide for the Development of Bicycle Facilities (2012) allows engineers the option of using dotted lines at intersections based on engineering judement. The dotted lines are intended to indicate to motorists and cyclists the area where it is appropriate for motorists to merge into the bicycle lane. It also says the following (Chapter 4.8):

State vehicle or traffic codes should be consulted as well, as the presence of a solid bike lane line at the approach to an intersection may discourage motorists from merging before turning right, as required by law in some states. […] In such cases, a dotted marking should be used or the bike lane should be dropped on intersection approaches where right turns are permitted.

The MnMUTCD also allows the optional use of a dotted line, though there is little guidance provided about when it is appropriate. However, the MnDOT Bikeway Facility Design Manual (2007) mostly avoids the question and simply recommends placing the bike lane to the left of right-turning motorists.

No Dashed Lines at intersection of Park Avenue & 31st Street.

This is not a perfect solution, primarily because we have learned that many motorists do not merge into the bicycle lanes prior to executing turns, and many motorists and cyclists are not aware that this is the current state law. In addition, some cyclists do not feel comfortable with the idea of motorists merging into bicycle lanes under any circumstances. Local agencies are not using a single strategy, and one will encounter bicycle lanes that are dotted at some intersections and not dotted at others, even along the same roadway.

At the same time, many communities, including the City of Minneapolis, are experimenting with markings referred to as “bicycle boxes” or “bike boxes” as a different potential strategy to reduce “right-hook” crashes. Bike boxes, which are typically only installed at signalized intersections, have many intended functions, but there are two specific functions relevant to the discussion of “right-hook” crashes. The first is that they implement an advanced stop line and often prohibit right-turn-on-red, which allows bicyclists to pull ahead of  motor vehicles stopped for a red light and establish position within the motorists primary field of vision. The second is that they do not used dotted lines, thus discouraging motorists from merging into bicycle lanes before turning right. Instead, motorists are asked to yield to through bicyclists, then turn across the bicycle lane from the motor vehicle lane. This, it seems, is in conflict with current state law.

Typical Bike Box installation. Notice the white lines outlining the green box are all solid, rather than dashed. (image via Portland Mercury)

Bicycle boxes are not currently an approved marking in the MUTCD, and communities that wish to use them must request permission to experiment with the markings from the FHWA. The City of Minneapolis has done this for bicycle boxes that are currently in-place in at least one location (the Franklin Avenue/East River Parkway/27th Avenue intersection).

The City of Portland is currently experimenting with bicycle boxes in a number of locations as well. Sarah Mirk reported on the Portland Mercury Blogtown that the City of Portland recently provided the FHWA with a progress report of the performance of the experimental markings. Among the initial findings is that the number of right-hook crashes has increased at several locations where the experimental bike boxes are installed. Ms. Mirk provided the following commentary and summary of the memo to the FHWA:

What appears to be leading to the new crashes in that people are biking through the intersection faster, overtaking cars that are turning right. While the bike boxes have been good at stopping right hooks when both the car and bike are starting up from being stopped at a light, 88 percent of the crashes happened at a “stale” green—not from a dead-stop but from a turning car striking a cyclist who’s in motion, pedaling down the block and through a green-lit intersection.

The question of whether or not motorists should be instructed to merge into bike lanes is unresolved, and recent news articles indicate that the City of Minneapolis has requested clarification from the state legislature about the intent of the law requiring motorists to merge.

I’m probably not hiding my bias very well. Laws requiring motorists to merge into the bike lane make sense to me, both as a professional engineer and also as a cyclist. However, it’s also true that this safety strategy isn’t really compatible with some of the newer bicycle facility types (e.g. on-street two-way cycle tracks, bike boxes). As the range of bicycle facility types continues to expand, our directions to drivers on how to safely interact with bicyclists is also going to become more complex. The need for a more complex safety message is not an advantage, but it may be necessary.