Tesla's winning the self-driving race — so why is Washington trying to slow it down?

Washington has a messaging problem on self-driving cars — and it’s becoming harder to ignore.Regulators and politicians keep telling Americans that autonomous vehicles are the future. Safer roads. Fewer accidents. Smarter mobility. That’s the pitch. But at the same time, they’re turning up the heat on the one company that has already put the technology into millions of vehicles: Tesla.Tesla has millions of vehicles generating data. Most competitors don’t. That raises a bigger question: control....