Bike Lanes Don’t Lead to Congestion, But Some of Them Should

After bike lanes were installed in Minneapolis, there were more cars per unit of road space, but still not enough to meet the threshold for congestion.

Gretchen Johnson and Aaron Johnson have posted a nice debunking of typical “war on cars” rhetoric over at fivethirtyeight.

Johnson and Johnson gathered before-and-after traffic data from 45 miles of streets where Minneapolis installed bike lanes. They also looked at how Brooklyn’s Prospect Park West bike lane affected traffic conditions.

They found, in short, that after the installation of bike lanes, traffic conditions did not meet the threshold of “heavy congestion,” and the impact on space for motor vehicles was moderate enough that drivers’ travel times would likely be unaffected.

None of the 10 Minneapolis streets reached a level where “minor incidents can cause traffic jams,” although the bike lanes did edge two streets into the “mild to moderate” congestion category. The authors, a transportation consultant and aeronautics Ph.D., write that this “mild to moderate” level is “where traffic is still moving smoothly but you might notice that it’s a bit harder to move from one lane to another.”

Meanwhile, on Prospect Park West, NYC DOT reported that there was no evidence that travel times increased after the installation of a two-way protected bike lane. The two Johnsons, after reviewing the data, say “we agree.”

These are the findings you would expect to see when a street redesign converts excess space for cars into room for bikes. Afterward, there’s less wide-open road space encouraging motorists to drive fast, and on Prospect Park West the city observed a big reduction in speeding after the bike lane was installed.

The Johnsons offer a compelling rebuttal to overheated “war on cars” rhetoric, but the piece is also couched in the assumption that bike lanes are only worth it if they don’t lead to congestion. “Bike Lanes Don’t Cause Traffic Jams If You’re Smart About Where You Build Them,” reads the headline. Later on, they set up their data dive like so: “It seems that unless a ton of people start commuting by bicycle, giving away a lane would cause increased car traffic. But is this really the case?”

But sometimes the smart place to put bike infrastructure is exactly where it may lead to congestion. Why? Because no city can “get a ton of people to start commuting by bicycle” without a well-connected network of bike lanes. To create a seamless network with no gaps — no places where people feel too stressed out or scared to bike — you’ll probably have to add bike lanes to streets where they’ll lead to some congestion. And that’s okay — especially if everyone is safer as a result.

In American cities that are building protected bike lanes, there still tend to be gaps in the bikeways where traffic is really intense. In Manhattan, for instance, protected bike lanes on First and Second Avenue give way to sharrows on some stretches, to avoid creating congestion. While the safer bike lanes have led to significant increases in cycling, those gaps in the network will have to be filled in to entice the huge segment of the population who are “interested but concerned” about cycling to give it a try.

The fivethirtyeight analysis will come in handy in many cases, to show that traffic hasn’t backed up where bike lanes were installed. But to create great bike networks that shift a lot of trips from driving to cycling, we’ll need to build some bike lanes that claim space on the most trafficked streets.

23 thoughts on Bike Lanes Don’t Lead to Congestion, But Some of Them Should

  1. I would guess that this is different for New York, since most of the bike lanes installed have been done so without the sacrifice of any car lanes.

  2. Looks like bike lanes take roads from “woefully underutilized” to “moderately underutilized”…

  3. People (or really, one very vocal older newspaper columnist) were up in arms when Philadelphia started putting bike lanes in Center City. The city now has one of the highest rates of bicycle commuting in the country and traffic is pretty normal.

  4. Are “you might notice it’s a bit harder to double park” or “it may be less easy to exceed the speed limit” included among the “congestion” benchmarks? Because those are the things that are bugging the bike lane opponents over on Prospect Park West.

  5. From a balanced perspective, this is a great trade-off. Fundamentalists will probably just see unacceptable impacts to traffic, though.

  6. FYI that your data demonstrates that bike lanes do indeed lead to more congestion…or higher V/C ratios. In every case the congestion levels increased. Not saying that is bad, but at least come up with a new title that does not confuse a reader when the first chart tells a very different story.

  7. Overall, I am glad to hear and hope this leads to less fighting about the impact of bike lanes.

    But I do find it oxymoronic that if speeding is reduced that travel times aren’t therefore increased. How do you get slower speeds but the same travel times?

  8. Isn’t the point, though, that congestion really isn’t a continuous scale but rather a threshold? Because when the number of cars increases, the travel time doesn’t increase up to a certain point.

  9. Because most drivers race from red light to red light. In other words, normally their speed swings from really fast (speeding) to really slow (stopped). In other words, there are infinitely many ways to get the same average speed (which is what determines your time), and those that get the same average via large extremes are the most dangerous for everybody. So traffic calming — like adding bike lanes — “smooths” out the extremes without much changing the average.

  10. I agree with Dave that it’s a little confusing if you don’t know that congestion in this context means a threshold, as And pointed out. Most of us think of congestion as being a continuous scale, hence the reason the headline is confusing. What is missing from the graphic, and the part that would make it more clear, is showing average travel times. Together, that would make a more clear point. It would also be justification for adding bike lanes because we’re getting better utilization out of our roads, i.e. they are being used more efficiently.

  11. In addition to the red light issue, traffic flow sometimes actually increases at lower speeds (depending on the specific scenario). The higher the speed, the greater the gaps between vehicles as most drivers allow a two second or so gap between their car and the one in front of them, so at higher speeds the gap is physically larger. I’m not a traffic engineer so someone else may be able to explain this a lot better.

  12. Though I am a cyclist (mercifully immune to pretty much all car traffic congestion), when I saw the chart, I immediately thought that this data isn’t going to help our case at all. Drivers will see this chart, and will likely read it as: bike lanes increase congestion.

  13. people who complain about not getting to break the law will always be seen as what they are: irrational and entitled

  14. Do any of the streets in the study have bus routes? Was bus travel time or reliability affected?

  15. I drove in Minneapolis/St.Paul with my cousin who lived there at the time. As we went along at about 25mph, she complained about how congested traffic was, I laughed so much I had to pull over because as a Chicagoan I knew this was not congestion. My point is the each city’s traffic patterns are unique

  16. Correct that in general a regular bike lane is just space taken from the excess width of existing lanes rather than removing a lane, though this is not true for specific types and locations of bike lanes.

    Most of the big green protected bikeways on Manhattan Avenues have taken car lanes, but the “before” was a completely insane amount of lanes. Compare 1st or 2nd Aves (with bikeways) to 3rd Ave or 6th Ave (without) to see what I mean. Crossing the latter two on foot really sucks compared to crossing the first two.

  17. Your deep concern for and commitment to truly multimodal complete streets will no doubt build support for these road diets among transit advocates and bus riders.

  18. Bicycles slowly moving in front of a vehicle leads to congestion, just as long as they stay in their bike lane all should be good.

  19. this isn’t true in the way you mean it. in moving from an uncongested state with low flow to a congested state with high flow, density rises and speed falls. but slowing cars down more than they would otherwise does not raise traffic flow; it lowers it.

    here’s an analogy. reducing the supply of oil (or whatever else) raises its price, because a higher price reduces demand to the level of supply. but lowering the price of oil–by some price control or a reduction in demand–will not raise the supply of oil back to its original level; it will lower it even further.

  20. I wonder if it’s the patterns themselves that are unique, or the local people’s perceptions of them? As a lifelong New Yorker, 25 MPH sounds to me like “traffic moving smoothly” and in fact that’s the speed limit now in most of NYC. I would think that for the most part the patterns are the same from city to city in similar neighborhoods.

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