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[[File:Four-ramp.png|thumb|250px|right|A diagram of a diamond interchange, the most common kind of four-ramp interchange. All traffic attempting to enter the blue highway northbound will enter via ramp 'X.']]A '''four-ramp interchange''' is the most common interchange in the [[United States]] where a non controlled access highway intersects a controlled access highway: commonly an interstate/turnpike or other type of freeway.

'''Four-ramp interchanges''' are desirable for hitchikers because they require all traffic attempting to head a given direction on a freeway to enter the freeway on a single ramp. The hitchhiker stands on this ramp and is then exposed to all possible traffic entering the freeway.