> It takes time for even a Waymo to recognize a dangerous situation
Reaction time makes the math even better here. You travel v1 * reaction_time no matter what, before entering the deceleration regime. So if v1 gets smaller, you get to spend a greater proportion of time in the deceleration regime.
> linear deceleration.
After reaction time, stopping distance is pretty close to n^2. There's weird effects at high speed (contribution from drag) and at very low speed, but they have pretty modest contributions.
I was thinking more that how hard the brakes are applied likely varies based on uncertainty of a collision.
Without that these vehicles could only start braking when certainty crossed some arbitrary threshold.