Max speed stopping with TACC

[Zeke5]

Just curious: Today I was on a straight road with TACC set at 55 and there was a big box van already stopped at a red light in front of me about 200 yds out and wanted to see how TACC behaved. TACC did bring me to complete stop, but it seemed a bit late to recognize stopped truck in lane and start slowing down ... was a pretty jarring deceleration and made for a bit of a nerve wracking experience. (Foot was hovering over brake just in case of course)

So, what’s the fastest you’ve gone and had TACC bring you to stop for a stopped vehicle or object in path? What is the recommended max speed to even allow TACC to handle this kind of stop unassisted? Have you seen its reaction distance reduced based on size of vehicle in path? How about a motorcycle?

I do not have FSD.

 

[dwooder]

TACC is not accurate with stationary objects, sometimes it wont stop.

 

[Tam]

...So, what’s the fastest you’ve gone and had TACC bring you to stop for a stopped vehicle or object in path?...

As a rule, you should assume that all RADAR dependent system, including Autopilot/TACC/FSD, does not stop for a stationary object. If it does, that is a bonus but that is not how the RADAR system is designed for.

The manual says:

"Traffic-Aware Cruise Control cannot detect all objects and, especially in situations when you are driving over 50 mph (80 km/h), may not brake/decelerate when a vehicle or object is only partially in the driving lane or when a vehicle you are following moves out of your driving path and a stationary or slow-moving vehicle or object is in front of you."

All RADAR dependent systems are designed for moving objects running at the same direction as your car is moving.

https://www.wired.com/story/tesla-autopilot-why-crash-radar/

Although your TACC can work from 0 to 90MPH, the slower the speed, especially, under 50MPH, the better chance it can stop for stationary obstacles. Remember again, it is not a guarantee!

 

[Johnny Vector]

In my recent 1200 miles of road tripping, I found that TACC worked great if the traffic speed was changing by less than 20-30 mph. E.g. between 40 and 60, or between stopped and 25 mph. With larger differences it waits too long when slowing down, causing me to yell "Why are you using the friction brakes, Rob???" (Rob is the car's name; see avatar to the left.) I have the follow distance maxed out, and the mode set to Chill, but TACC is still not as good as I am at looking ahead to see that traffic ahead is stopped. Having to use the friction brakes on the highway is a failure, Rob. What would your Kelda think?