New York Times technology journalist and one time racer John Markoff likes cycling around on the roads of the San Francisco Peninsula, favoring the hilly roads of Portola Valley.

Earlier this summer, the 61 year old rider & writer crashed hard but doesn’t remember how it happened. He used his GPS to track his movements and see precisely where he hit the deck. In his latest science story, Markoff describes how bike mounted GPS units are used to reconstruct bike crashes, especially when car insurance and lawyers are involved.

You can also follow Markoff’s riding on Strava.