Car safety assist dropping speed automatically

Would this be considered good UX if the car in safety assist mode would drop the speed automatically to adjust with the car in front instead of informing the driver of getting too close?

This is currently used by Tesla in autopilot mode which is not really an "assist" as driver is taking very little to no part in controlling the vehicle.

In my opinion this would become vital in preventing rear collision, but could also affect drivers who are not used to this.