You just need to bump the wheel every 15 seconds or so. The required interval seems to vary a certain amount, but in boring, easy, bumper to bumper traffic, where it makes the most sense, that's all that's required, in my experience at least.

> it does stop the car

More specifically: in my tests, it eventually disengages autopilot as well as adaptive cruise control (which only controls the break and acceleration) while beeping loudly and harshly. This has the affect of slowly causing the car to decelerate.