Drivers should scan how many seconds down the road?

Answer 1

At least 30 to a full minute. And not just straight ahead either ... need to constantly scan side to side, check your mirrors frequently, and be aware of what is behind you, too. Leave yourself an "out" ... had two meanings:

# you are invisible and nobody can see you on the road # leave yourself room enough between stopped vehicles to get around it if the car in front stalls out.