How far apart should cones be for parallel parking?

For a straight truck. I have been putting a cone at the front bumper and rear of truck and practicing like that. Should the cones be further apart?

 

Ideally you want at least 4 cones that make a rectangular "box" that becomes the "parking space". Add 6 feet to the overall length of the truck (28' straight truck = 32' long X 9' wide box). You can practice blind and driver side parallel parking that way. Run caution tape or rope between the 2 "curb side" cones to mimic an immovable object like a wall or another truck. This will help you gauge depth perception and the swing of the overhang in back.

 

Thank you.