For years, Dutch cities have been building protected intersections: crossings that are designed to reduce the risk of cyclists getting hit by turning cars. Last week, in Davis, California, the very first protected intersection opened for traffic in the US — and it's gotten positive reviews from locals so far.

The rationale for these new intersections is straightforward. Protected bike lanes — which are physically separated from the street by a curb or other barrier and have spread widely in the US over the past decade — have significantly cut down on cyclist injuries and deaths. But even on streets that have them, cyclists still have to ride through intersections right next to car traffic — and evidence suggests that the majority of crashes occur at intersections, when turning cars are most likely to hit them.

Protected intersections solve this problem with separated channels for cyclists to ride through. They also orient drivers so that they can more easily see pedestrians and bikes when they're turning. As Michael Andersen at People for Bikes puts it, "Instead of forcing people in cars and on bikes alike to look constantly over their shoulders for one another, protected intersections arrange traffic so that everyone can see what's going on simply by looking forward."

How the new protected intersection works

Davis's new intersection is intended to solve one big problem in particular: when a cyclist, going straight, is next to a car that's turning right.

With most protected bike lanes, the barrier disappears at the intersection. Right-turning cars either mingle with bike traffic or are forced to merge through it — both of which require drivers to spot bikes in their mirrors and avoid them. Often they don't see cyclists, leading to a type of accident called the right hook.

Davis's new intersection — like the ones in the Netherlands — includes special islands at the corners. Cyclists going straight can ride to the right of them, and the islands' shape ensures that right-turning cars will encounter these cyclists straight on. Instead of looking over their shoulders to see bikes, drivers see them directly in front of their windshields.

The islands also make pedestrians more visible to drivers in the same way and give them a shorter distance to walk when crossing the street. And the islands force cars to take turns more slowly, further reducing the chance of a crash.

Finally, the intersection gives cyclists a new safer, slower option for making one of the more dangerous moves: a left turn. While they can still merge over to the turning lane and turn left through the intersection like a car (the top blue line in the diagram above), they can alternatively act a bit more like a pedestrian, proceeding across the intersection, then crossing it again at a perpendicular angle after the light has turned (the bottom blue line).

Many cyclists do this already — it's called a hook turn — but the new design makes both legs of this maneuver safer.

Why infrastructure design is so important

Davis isn't the only city building protected intersections: Austin has one in an as-yet-undeveloped subdivision, and Boston and Salt Lake City have plans to build several over the next few years. All this is part of a boom in bike-specific infrastructure across the US, as many cities try to get more people to bike and walk to cut down on traffic.

It's happening for a good reason. Plenty of research shows that the presence of protected bike lanes, for instance, is one of the strongest factors that make people willing to try biking in a city. The world's cities with the highest rates of bicycling — such as Copenhagen and Amsterdam — have the highest amounts of protected bike lanes and trails, and research shows this correlation also holds for US cities. Davis, which has held the US title for the highest percentage of bike commuters for decades and has an extensive bike lane network, is the perfect example of this.

The basic reason is that absent this infrastructure, roads across the US are often designed solely with cars in mind. There might be a core group of hardcore bikers who are willing to ride right next to car traffic, but it's pretty small — and reaching new people requires intentionally designing roads to make biking safe.

Martha Roskowski of the advocacy group People for Bikes has a great analogy for this idea. Riding a bike in the streets, like a car, is akin to skiing a black diamond run down a mountain. A minority of bikers might do it (and even enjoy it), but to make most people comfortable with the idea of biking in a city, we need the equivalent of green circle and blue square ski routes — protected lanes and intersections. More importantly, these need to make up a linked, cohesive system, so people can bike from home to work, for instance, without needing to brave a black diamond along the way.