If there is enough time to get down to 20MPH, there is more than enough time to miss the object.
It's physics time again... braking distance is a square function, not linear...
Roughly speaking it is x˛ ÷ 20 + x = Overall stopping distance in feet. where X = speed
I think some of these distances are a bit long based on modern tires and brakes, but here goes anyway...
Using some
Intarweb data we see that it only takes 40 feet to make an unplanned stop from 20 MPH. and only 20 feet of that is actually stopping. From 60MPH, it takes 240 feet, take away the last 20 feet for your 20 MPH stop, and you need 220 feet to get from 60 to 20.
Hope all the deer are kind enough to step out in front of you 2/3rds of a football field in front of you.
Most of the time braking should be done after making a directional change, but in todays ABS world, you can even steer after you brake. The problem is people don't! They stare at the object they are going to hit pedal jammed to the floor, and arms locked braced for impact.
Turn the F'ing wheeel!