whether they activate or not I think its good practice to check for tailgaters anyway. Us old schoolers were taught to slow down using the gears (I guess from the drum brake era?).
I have a licence to drive a minibus up to 12 seats but was going to be driving school children on a school trip so had to do a (UK) council driving course. During the driving part of the test I changed down gears approaching a junction, arriving at the stop light in second gear, handbrake on and into neutral. I was told that if I did that again, they would fail me!
Apparently they now want you to approach a junction without changing down, stop and then select the low gear to pull away. I challenged this as I said approaching a junction or roundabout I would be in the wrong gear if the way ahead cleared. They said, "do it again and they would fail me". Crazy, so I did what they wanted, then drove as I was taught 40+ years ago after I had my council approved driving certificate. When I asked the students how they were taught to drive they said the same way, approach in the gear you are in and sort it out at the junction. To me, that probably explains why there are so many rear-end collisions (exacerbated by people driving too close).
Jeff, driving for over 40 years, no accidents, one speeding ticket and paying 50p a day for fully comprehensive insurance. Go figure.