With regard to the post below it is, of course, worth saying that engineering our cities so as to support the needs of all the users of our streets, rather than the desire of suburban commuters to move very quickly, is at times literally a matter of life and death. Take the example of Alice Swanson the 22 year-old bicycle commuter killed yesterday as she attempted to bike west on R Street through the intersection with 20th Street by a garbage truck that seems to have turned right without looking to see if anyone was in the bike lane moving forward.

This particular intersection is not an especially dangerous one, in my view, which goes to show that terrible things can happen even with decent traffic engineering. But it also serves as a reminder that at other, worse-designed elements of our streets, huge risks are taken every day with the safety of pedestrians and cyclists.