Bike lanes beget bicycles

Meta-research shows that more bike lanes generate more cyclists:

Buehler and Pucher found that the presence of off-road bike paths and on-street bike lanes were, by far, the biggest determinant of cycling rates in cities. And that’s true even after you control for a variety of other factors like how hot or cold a city is, how much rain falls, how dense the city is, how high gas prices are, the type of people that live there, or how safe it is to cycle. None of those things seem to matter quite as much. The results, the authors write, “are consistent with the hypothesis that bike lanes and bike paths encourage cycling.”
If that sounds overly obvious, the authors do note that previous research was somewhat scattered on this question. A few studies had found that more bike lanes in a city were associated with more cycling, though it was unclear which was causing which.

The tricky question here is the direction of causation, and it’s likely that causation runs both ways. To claim that bike lanes generate cycling we really need a plausible hypothesis for why that might happen. Thankfully, it’s not that hard: bike lanes lower the cost of cycling because they’re more pleasant and less dangerous. Lower prices mean increased demand for cycling.

OK, so building bike lanes makes cycling cheaper, which gets more people cycling. But that doesn’t mean they’re a good idea, unless more cycling is just inherently good. To decide whether it’s good policy to build more bike lanes we need to compare the cost of building them to the price that people are willing to pay to use them (plus any externalities). Hopefully that’s what’s being done, even though the local newspaper makes it sound as if the main issue is the strength of the cycling lobby!