Final answer:
To exit an interstate highway safely, you should start slowing down after moving into d) the deceleration lane, which is the correct area designated for vehicles to reduce speed before exiting.
Step-by-step explanation:
When exiting an interstate highway, the correct approach is to maintain your normal speed while on the main road and only start to slow down after you have moved into the deceleration lane. This ensures that the flow of traffic on the interstate is not impeded by vehicles slowing down prematurely.
The deceleration lane is specifically designed to provide a safe space for vehicles to slow down before exiting the highway, thus preventing potential rear-end collisions and maintaining the efficiency of the interstate traffic flow.
Therefore, the correct answer to the question of when to start slowing down when exiting an interstate highway is d) the deceleration lane. Remembering to make this maneuver in the deceleration lane is crucial for both safety and compliance with road rules.