Landmark Study Tests a Bike Network’s Effects on Safety and Ridership

Photo: Claudio Olivares Medina
Photo: Claudio Olivares Medina

Which is more important to making a city great for biking: the number of high-quality bikeways, or whether they’re connected to each other?

A new study from Spain offers an unexpected answer: The amount of biking actually tracks most closely with the number of bikeways, while the safety of biking tracks most closely with the connectedness of bikeways.

But if you want lots of people biking safely, you eventually need both.

The paper is unique because it draws on a once-in-a-generation opportunity to measure what happens when a big city that has very little biking makes a sudden, massive investment in a biking network.

Seville’s bike network was literally a Communist plot

Photo: Steven Vance.

The paper by R. Marqués and V. Hernández-Herrador, published this month in the journal Accident Analysis and Prevention, provides one of the first academic studies of one of the largest rapid bike-infrastructure investments in world history.

In 2003, the 2,200-year-old Spanish city of Seville (population 700,000) voted more Communists than usual onto its city council. (Yes, this is a thing that happens in Seville.) The left-wing party had pledged a major investment in bike transportation — and after they joined a coalition with the center-left Socialist party, they delivered. In 2007 alone, the city built 40 miles of protected bike lanes, a 542 percent increase over the existing 7 miles. It created an imperfect but connected network through the central city.

The evolution of Seville’s bikeway map, from 2006 (upper left) to 2010 (lower right). Source: Marqués Sillero, R. (2011) via Pensando el Territorio.

Another 46 miles were installed over the next six years, along with a popular new bike-sharing system. (These six years overlapped, it’s worth noting, with the global financial crisis and a particularly deep recession in Spain — national unemployment peaked at 27 percent in 2013. Seville’s tourism-heavy region, Andalucia, had the worst job market in the country, and the city itself fared only a bit better.)

Two things started happening in Seville almost immediately: The number of bike trips soared and the risk of a bike trip plummeted.

Source: R. Marqués and V. Hernández-Herrador (2017).

The basic story of Seville’s bike boom has been known for a few years. But in their study, Marqués and Hernández-Herrador wanted to know what had happened in what order.

Was biking safer because the protected bike lane network had gotten more people biking (the so-called “safety in numbers” theory)? Or was biking safer because the new barriers reduced collisions directly? And did the change come gradually, or all at once?

Photo: Claudio Olivares Medina.

To explore these questions, the researchers considered four main policy variables:

  • The total length of all bikeways in Seville
  • Whether or not the “starter” network of 2007 had been built (a yes or no question)
  • The number of bike trips in Seville per year
  • The risk that a given bike trip would involve a death or serious injury

That second item is what made their study most unique. Many cities build low-stress networks gradually. Only Seville had built a large connected network in a single year.

“Since the cycle paths existing before 2007 were few and unconnected, there was a qualitative change between 2006 and 2007,” the authors write.

In other words, Seville gave scientists a chance to test an important question: How much does bike network connectedness matter?

Here’s what they found: bike network connectedness seems to immediately pay off in the form of lower risk to people biking. The risk of a biking trip in Seville seems to have fallen dramatically in 2007 and stayed mostly flat afterward. No other single variable predicted bike safety as well as that single yes/no question: Has a network been built yet?

More accurate still was a formula that took into account both variables — the length of bikeways built and that yes/no question about whether or not the network had been connected.

In other words: Generally speaking, every additional mile of protected bike lane somewhere in the city improved safety. But network connections improved safety most.

The network itself didn’t directly boost ridership — at least, not immediately

Photo: Bike Texas.

The most surprising finding of Marqués and Hernández-Herrador is probably that the network connections didn’t correlate very well with ridership.

Instead of jumping abruptly as soon as the network was in place, the number of people biking in Seville rose steadily.

Here’s what the authors say about this:

Our interpretation is that the primary cause for the aforementioned big drop of risk was the implementation of the network of bikeways, and that the subsequent reduction of risk was the primary cause for the increase in the number of bicycle trips.

It’s worth adding that the authors also believe that even as safety was boosting ridership, ridership was also improving safety. They describe their findings as “an independent numerical confirmation of the theory of ‘safety in numbers,'” proposed by Peter Jacobsen: the rising probability of seeing bikes on the road seems to have boosted safety on streets without dedicated bike lanes.

One possibility Marqués and Hernández-Herrador don’t explore is that the network did increase ridership directly, just not immediately. It’s plausible that infrastructure-related biking increases are inherently gradual. New bike lanes may lie in wait for their future users to experience a triggering event like a new home, new job, fuel price spike, or personal income shock.

In any case, the paper offers strong evidence that even massive network investments can’t drive instantaneous ridership change.

In an email, American biking researcher John Pucher called the article “a landmark study”:

No one knows cycling in Sevilla better than Prof. Marqués. His data for Sevilla are superb, his statistical analysis right on target, and his conclusions are definitely justified by the data and analysis. This is a very important article because it examines more carefully than any previous academic article the various impacts of expanded and improved cycling facilities over time.

Pucher said the new finding “fully reinforces” his paper published in February in the American Journal of Public Health, which drew on an overview of data from many affluent countries to conclude that “constructing physically separated, protected cycle tracks and providing key connections within the overall bikeway network are the most effective bikeway investments.”

“Simply racking up total bikeway mileage by putting down stripes for unprotected bike lanes is obviously cheaper,” Pucher said. “But it does not attract nearly as much new cycling.”

17 thoughts on Landmark Study Tests a Bike Network’s Effects on Safety and Ridership

  1. The number of people who would travel by bicycle if the fully understood it was possible for them, and all the benefits, is very large. But most people don’t think of it. No one is advertising it on a large scale.

    A piece of bike infrastructure with people riding bicycles on it is like outdoor advertising.

  2. If it became a “trendy” thing like standing desks or fidget spinners, suddenly people would embrace it.

  3. I’m in Barcelona at the moment, and some observations:

    Lots of cyclists here, and protected bike lanes are common, but the density of the lane network is not high; many streets with no lanes or unprotected ones.

    Bizarrely, the local bike share system -discourages- tourists. You can only unlock a bike with a key, and you can only get a key by signing up online, and having it mailed to an address in Catalonia. Apparently, this was in response to lobbying by bike renters, who didn’t want the competition.

    The streets are designed in a pattern I’ve never seen before; as a pedestrian, when you approach an intersection, you actually have to turn the corner and walk a few meters to find a crosswalk. This is a) inconvenient, because you have to walk farther to cross, but b) very likely safer, because a car that turns the corner is now facing directly toward you, and -will- see you; they slow or stop as you cross. It’s unusual, but I think it works.

    Lots of scooters, and lots of designated parking areas for scooters.

  4. Most of all cycling needs a lot of quality bike-friendly infrastructure if it ever hopes to compete with the automobile.

  5. I’ve been in Barcelona for two days now and I had exactly that same set of observations about the strange diamond-shaped intersections in the Eixemple district – probably safer, but extremely frustrating, and occasionally confusing (since I accidentally continue around the corner instead of crossing the street in the same direction I meant to keep going).

  6. Yes, even the auto was dependent on a major lobbying effort for quality infrastructure before it could take off.

  7. Is there any study of bikelash outside the US, or are drivers in these cities where cycling has suddenly taken off just inherently more civil?

  8. Even just paved roads in general–before GM lobbied for it, many (most?) secondary roads were completely unsuitable for cars.

  9. I’ve only been to Barcelona once, back in 2012 and I do not recall the crosswalks being like that but I also wasn’t nearly as into urban design back then. I’m going back during christmas time this year and will definitely be sure to check it out, thanks for the info.

    It’s crazy to me how popular scooters are in Barcelona compared to how unpopular they seem to be here in the US. I live in Denver and <50cc scooters can be parked in the ROW and registration is only $15 for three years, so there are some decent government incentives for them. What I would like to see is dedicated on street parking for bikes and scooters and even motorcycles in the area between the end of street parking and the intersection. They don't obscure your view when trying to cross/turn and would be a huge incentive to these alternate forms of transportation.

  10. I do know for a fact that Dutch motorists don’t take too kindly to bicyclists who wander into areas where biking is prohibited. Stern looks and honks abound.

  11. And streets in cities were not dedicated to car traffic, but had an anarchic mix of pedestrian, streetcar, horse, and bicycle traffic which prevented anyone from going much faster than 10mph. Much lobbying and campaigning was needed to rip out the streetcars and force pedestrians onto sidewalks to make way for motorcars to speed.

  12. You have to walk around the diamond to cross at most intersections. The problem would be solve by making the diamonds sidewalks. They were originally invented as public places, but have degenerated into parking lots.

    This is a typical intersection from above. The current crosswalks are visible as white dotted lines. I added red lines to show where the cubs should run, and blue lines to show where to crosswalks should be.

    Note that you don’t have to treat all four corners this way. The worst thing about this mess is that it doesn’t even provide much parking. You could indent the cubs and have parallel parking up to the crosswalks and lose almost no spots. In fact you might even gain parking spaces, not sure.

  13. “Bikelash” is a nonsensical concept. There are prats out there who will see any cyclist as a threat to their “ownership” of the road. However the extent to which they try it, and the extent to which they get away with it, is tied primarily to the influence of malignant journalism rather than the installation of bicycle infrastructure.

    Local experience here in Melbourne in southeastern Australia is that motorist hostility to cyclists has gone down proportionally with increase in cycling numbers and cycle lanes on-road. Quite the converse of any backlash.

    In Sydney, in eastern Australia, the situation is very different. There has been a sharp increase in the reported rate of hostile interactions but this has followed constant hostility from popular radio “shock-jocks” and hostile populist actions by government stemming from that journalism, including fines in excess of $Au300 for not wearing a helmet when riding. Again, though, there is no perceptible relationship with increased levels of riding so it belies the concept of “bikelash”.

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