Ok sure. If you drive a car, try slowing 10kph in 5 seconds. It
seems gentle but the driver behind still needs reaction time. If he
bang you, he must be a daydreaming cock but chance of an accident
still increases. If he is going down slope, higher chance too.
But that's the way SAF wants it, we should jam brake. Even if we
are willing to take the punishment, we should try to follow the law
as much as possible.
Experience: I have been v-com countless times.
Lets do some math here, slowing 10kph in 5 secs.
At 60km/h you would travel 83.3 meters in 5 secs.
60km/60mins = 1km/min
While at 50km/h you would travel 69.4 meters in 5 sec.
50km/60mins = 0.833km/min
The gap between vehicles would have to be Less than 14meters in
order for the rear vehicle to hit your rear if he did not react at
all.
Seems pretty likely for an accident? But wait, thats not
all.
Dont forget that you need time to Acclerate to 60kph. You
already spent 5 secs slowing down, so that means you only have 4
secs to acclerate.
4 secs is quite alot of time to acclerate, but what about the
rear vehicle? Unless you are tailgating (which means you are
already paying attention to the front vehicle), otherwise you would
simply have not reacted within in that 4 secs to even catch up with
the MID vehicle infront to 60kph.
Basically, what im trying to say is that a momentarily increase
of speed from 50kph followed by a momentarily decrease of
speed to 50kph within 9 seconds would not be enough to create
rear-end collision because the driver behind would have have seen
your brake lights faster than he can catch up.
Thats the way saf wants it? Follow Law? Good soldier, saf has
taught you well! 
