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Shared Bike Turn Lanes

I was working with a client recently where we briefly considered installing a shared right-turn lane and bike lane. This is a relatively new strategy used in locations where there is not enough roadway width to maintain a standard 5′ bike lane through an intersection – typically because that roadway space is used for right-turn lanes for motorists. There are some nice photos and renderings of what this looks like in the NACTO Urban Bikeway Design Guide.

This design strategy can be considered under the following conditions:

  • traffic volumes in the turn lane are less than volumes in the through lane.
  • vehicle queues in the through lane often extend further from the intersection than the end of the bike lane
  • the right-turn lane is generously sized to still permit vehicles to turn when a cyclist is present
  • there is a receiving lane (bike lane or standard lane) across the intersection (i.e. cyclists and motorists are not merging into a single lane after passing the intersection)

The Federal MUTCD currently does not permit using a dashed line to delineate bikes from right-turning vehicles within a single lane, but it does permit using sharrows to direct cyclists to hug the left side of the turn lane so turning vehicles can pass on the right.

I’m not aware of this strategy being formally used anywhere within the state of MN, although there are many locations where cyclists regularly do this – even with the tacit approval of the governing agency. One of the best examples is in the westbound bike lane that ends several hundred feet east of Cretin Avenue in Saint Paul. The striping and signage at this location pretty clearly guide cyclists to merge with turning vehicles (rather than merge with through vehicles), and to proceed through the intersection from a turn-only lane, although the City and County stop short of making this movement formal or legal.

marshall-ave-oblique by VeloTraffic, on Flickr

marshall-ave-oblique by VeloTraffic, on Flickr

In the following photo, when the bike lane ends, the striping clearly suggests that cyclists should remain in the turn lane (if the engineers wanted to direct cyclists to merge into the through lanes, the dashed white line would connect to the right side of the bike lane rather than the left – or they could have not included the dashed line at all).

marshall-ave-bike-lane-ends by VeloTraffic, on Flickr

marshall-ave-bike-lane-ends by VeloTraffic, on Flickr

The lane is clearly marked as a right turn lane, and the engineers even went so far as to explicitly post that MetroTransit buses are exempt and permitted to go straight from the turn lane (but no mention of bikes being exempt).

marshall-ave-mt-exempt by VeloTraffic, on Flickr

marshall-ave-mt-exempt by VeloTraffic, on Flickr

The following photo shows a cyclist choosing to stay in the right turn lane rather than merge with through traffic. This cyclist will proceed to the front of the right-turn lane, wait for a green light, then proceed through the intersection.

marshall-ave-cyclist by VeloTraffic, on Flickr

marshall-ave-cyclist by VeloTraffic, on Flickr

This is a much more convenient movement for the cyclist than merging with through traffic. As the photo shows, when the cyclist reaches the end of the bike lane, he has already passed many vehicles in the queue. This cyclist must then either squeeze into the middle of the vehicle queue to proceed through the intersection, then merge back into the rightmost lane after passing through the intersection, or he can just stay in the right lane. It’s advantageous for all users (including motorists) for cyclists to remain in the turn lane in this location – even if that means making an illegal movement from a turn lane.

So why the reluctance by agencies to formally adopt this strategy (i.e., why hasn’t the City or County posted a “Bikes Exempt” sign at this location to legalize what everyone is already doing anyway)? This strategy isn’t appropriate for all locations or all roadway conditions, but it’s definitely the best strategy in some locations. I understand a general reluctance to allow through movements from turn lanes, but I think there are clearly conditions where it should be permitted – especially locations where it is what the engineers intended in the first place.

1 comment to Shared Bike Turn Lanes

  • Charlie Quimby

    Second Avenue North at 4th Street is a dangerous intersection where cars in the right-turn-only lane often go straight through. The city ought to improve the pavement marking, which is worn away.

    Cyclists might think they can safely (and legally) turn right from the next lane to reach the 4th Street bike lane, which is along the left side of 4th.

    Be careful out there.

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