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Almost Bike Lanes

Bike lanes, generally, are a minimum of 5 feet wide. But a lot of roadways have shoulders that are less than five feet in width, which can be problematic for cyclists when this space is mistaken for bike lanes. Shoulders in the range of 2′ or less are narrow enough that it is pretty clear that they aren’t bike lanes. Shoulders in the 3′-4′ range, however, can be a bit problematic. These shoulders are generally not marked or signed as bike lanes, but they can look a bit like bike lanes, which can lead to confusion and unsafe situations as motorists and bicyclists interact. Not all shoulders 3′-4′ in width are unsafe places to ride a bicycle – there are a number of other factors to consider as well, but it is generally a less than desirable situation.

Bike Lane

Bike Lane

Minnesota State-Aid design standards require a “curb reaction distance” (a.k.a shoulders) on all new construction roadways. Often, there is minimal difference between what is required by state-aid standards for a roadway without bike lanes and what is required for a roadway with bike lanes.

For example, consider a new construction two-lane undivided Collector roadway without parking with projected ADT of 11,000 and design speed of 35 mph. Let’s presume the agency prefers 12 foot lane widths. State-aid design standards would require 4 foot shoulders whether the agency is constructing bike lanes or not. State-aid bikeway standards would require a 5-6 foot bike lane (the 2007 MnDOT Bikeway Facility Design Manual would recommend 6 feet…). In this hypothetical situation, the agency could choose between the following two construction scenarios:

  • construct a 32′ wide roadway (curb face to curb face), which will result in “almost bike lanes”
  • construct a 34′-36′ wide roadway (curb face to curb face), which will result in bike lanes consistent with design standards

In a new construction scenario, the difference in cost between a 32′ and 36′ roadway is not negligible, but it is also not substantial. Materials are cheap, labor is expensive – 4′ additional width requires additional materials, but little or no additional labor.

The decision seems pretty clear to me (not surprising given my obvious bias in favor of constructing bike facilities). In new construction scenarios, this is not a hard decision. In reconstruction scenarios there will often be things like trees in the way that make the decision much more difficult, and agencies still need to ask questions about how this hypothetical road fits into the overall transportation network. But I hope agencies are aware that in many cases, they are nearly building bike lanes whether they intend to or not – and that shoulder space is likely to get used by bicyclists wither it meets design standards or not. The additional cost for the 4′ difference in width is worth it – if nothing else for the ability to sign and mark the space as bike lanes that meet design standards (as this is how it is likely to be perceived by roadway users anyway), rather than being stuck with an “almost bike lane” scenario for perpetuity.

3 comments to Almost Bike Lanes

  • The additional cost for the 4′ difference in width is worth it – if nothing else for the ability to sign and mark the space as bike lanes that meet design standards

    I’m wondering if this is not considered a plus for many agencies. The City of Bloomington seems particularly reluctant to build formal bike lanes, preferring an unofficial, unmarked shoulder (often accompanied by a green “Bike Route” sign). 86th Street is the most egregious example of this, I think. Bike lanes are signed as bike lanes only approaching major intersections, where right-turn lanes form to their right. Otherwise, it’s just a general shoulder with no parking allowed. While most of the de facto bike lane is 5′ wide, there are portions where older storm drains reduce the rideable width to only about 2′. (Zoom in here, where for bonus points, the grates are parallel to the direction of bicycle travel.)

    Bloomington has also had such creative ideas as a “shared bike/parking lane”.

    All of these facilities have similar problems: they put inexperienced users in dangerous situations, and — as you note — even if an experienced user knows better than to use them, they provide a mechanism for motorists to resent bicyclists. There’s a “perfectly good” shoulder/bike lane, after all.

  • Z. Fechten

    Unless the road carries a lot of trucks, why not keep the original width and stripe 11 ft lanes?

    Widening the roadway will make it more likely that motor traffic will exceed the target speed, and unlike rural roads, wider lanes have not been shown to reduce crash rates on urban and suburban streets.*

    Also, that way they don’t have to fit more stormwater pollution control stuff in the right of way to address the added impervious area. Most of our rights of way are three rods (48.5 ft) wide, and it’s often a challenge to squeeze it in after width has been allocated to lanes, shoulders and sidewalks.


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