Street designers know that every inch of a roadway is precious. And though more inches are better when it comes to low-stress streets, sometimes they just aren’t there.

That’s when you consider doing what Washington DC just did, and install six-inch-wide $40 wheel stops directly on the stripe of a bike lane.

“Not up NACTO guidelines, but it works in a pinch,” DC Active Transportation Manager Jim Sebastian writes in an email.

Parking stops similar to these are one of the cheapest and most space-efficient of the many ways to protect bike lanes described in this matrix. It’s also one of the 14 captured on this infographic.

For more on the 1st Street design, see the Washington Area Bicycle Association’s post.