I don't believe vitz has automatic braking, just lift of the throttle and because it's cvt just keep a slight toe on the throttle when at a constant speed, the car will automatically switch to a more fuel-efficient ratio, I owned one for a brief period and with very little throttle press at 80km/h the car remained very quiet and rpms low,
I used these things and was getting 17- 18km/l with ac