Final answer:
When exiting an interstate highway, do not start to slow down until you have moved into the exit lane.
Step-by-step explanation:
When exiting an interstate highway, you should not start to slow down until you have moved into the exit lane.
This is important because it ensures that you maintain a safe speed and do not disrupt the flow of traffic on the interstate.
Slowing down too early can also lead to accidents or rear-end collisions if the vehicles behind you are not expecting it.