Why should your mirrors be adjusted to show the road behind you as well as part of your vehicle?

Question

Part of your vehicle should be visible in your mirrors so that you have a point of reference when judging how close other drivers and objects are to your vehicle.

Accepted Answer

Having part of the truck in the mirrors serves as a point of reference.

Answer

Having only the road in the mirrors would likely make the driver carsick.

Answer

It is illegal to have only the road in the mirrors.

Answer

The driver should be able to see the reflection of surrounding vehicles on the trailer.