For Whom the Dart Tows

RAY: The reason Tommy can tow me and I can't tow him is that his brakes have failed. Because I have a rope, if I tow him when I stop, he's going to slam into me. But if he tows me and when he needs to stop, he can signal me and by my stepping on the brakes --

TOM: You stop me.

RAY: Exactly. I will stop him as well. Pretty cute! Huh?

TOM: That's very good.

[ Car Talk Puzzler ]