In Rainy Areas, Protected Bike Lanes Can Cut Road Construction Costs

Image: MacKay Sposito.

pfb logo 100x22Michael Andersen blogs for The Green Lane Project, a PeopleForBikes program that helps U.S. cities build better bike lanes to create low-stress streets.

As protected bike lanes arrive in American suburbs, some city builders are making an unexpected discovery.

Not only are protected bike lanes by far the best way to make biking a pleasant transportation option for shorter trips — sometimes they can also significantly cut the cost of constructing new roads from scratch.

In the central cities where protected bike lanes first arrived, brand-new roads are rarely built. But now that many suburbs are upping their own game on bike infrastructure, a protected bike lane is being planned into streets from the get-go.

“It’s definitely something that we’re seeing more of,” said Zack Martin, engineering manager at the Washington State development consulting firm MacKay Sposito. “It’s coming up on I’d say most of the new arterial roads we’re looking at.”

In a blog post last month, Martin explained the unexpected reason protected bike lanes can save construction costs: rainwater.

Curb-protected bike lanes, his firm realized, can reduce the huge cost of managing rainwater that falls on pavement and then flows into streams and rivers. That runoff is a major source of water pollution, which is why the federal Clean Water Act requires local governments to minimize it. But in rainy parts of the country, preventing excess runoff from pavement that cars are driving on has also become a major cost factor in road construction.

From Martin’s post:

The primary benefit of a protected bike lane from a stormwater perspective is that runoff from the bike lane does not mix with runoff from the vehicle lane. This can be extremely beneficial in jurisdictions that consider the bike/pedestrian area a non-pollution generating surface (although some jurisdictions will still require it to be treated like water from the roadway). Plus this option also leads to the smallest increase in impervious surface.

The protected bike lane configuration can easily support curb cuts for rain gardens in either a continuous inflow or point load entry. This eliminates the need for inlets, manholes, and conveyance pipe. Protected bike lanes also can be built similar to a sidewalk and allow you to reduce the roadway width, both of which lower costs.

This means that protected bike lanes compare favorably to buffered or raised but otherwise unprotected bike lanes, which offer no way to distinguish between runoff from biking-walking and automotive surfaces.

Martin said in an interview Monday that the firm researched the subject in connection with a project in Vancouver, Wash., a suburb of Portland, Ore. He emphasized that such savings don’t apply in every jurisdiction — it depends on local circumstances and on how state and federal laws are interpreted at each level. But their discovery echoes that on a street like Cully Boulevard in Portland, which saved money when it was rebuilt in 2011 because the protected bike lane along each side didn’t require as much excavation as a wider road bed would have.

Quality bike infrastructure almost always saves tax dollars by improving health, reducing road wear and boosting road capacity. But sometimes the return on investment arrives sooner than others.

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  • Joe Linton

    Non-rainy areas need this too! Los Angeles County, CA, is not so rainy, but has huge water quality (pollution) and water quantity (flooding) problems that cost our municipalities billions to resolve.

  • Alex Brideau III

    It seems like bioswale-like treatments could be a logical next step/upgrade to a bollard-“protected” bike lane. Offers more protection from motor vehicles; more protection from conversion back to mixed-use lanes; and the potential to increase the urban shade canopy along a bike route; all along with the standard benefits of a bioswale.

    Phase 2 for the under-contruction Los Angeles St protected bike lane?

  • neroden

    Bioswale-protected bike lanes are and excellent idea.

  • I’m a little confused on this. Generally with protected bike lanes you still have gaps at intersections where the vehicle roadway intermingles with the bike lane, so presumably there is mixing of runoff there as well. Am I missing something, or is this really only true in relatively narrow circumstances where a bike lane is completely separated from a roadway for several blocks at a time (or more)?

  • The other benefit from PBLs comes from considering them as part of traffic studies and projections which is unfortunately not a common practice. Knowing that many people would be more willing to bike if it were not a gauntlet and that a good 40% of car trips are for under two miles, a distance which is quite easy to bike, it shouldn’t be very hard to estimate how many car trips could be biked instead. In many cases, that would likely lead to decently lower numbers of trips. If those fewer trips can reduce the “need” for an entire travel lane, that would also realize a substantial savings in itself in addition to the reasons mentioned above. Also, this is a great time for taking stock on access control as there’s usually little need for a full 12′ center turn lane if there are no driveways or intersecting streets and a street proposing a separated bikeway should keep those to a bare minimum. Cutting it down to say four feet saves that much more space and money.

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