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Interchange types

A completed SPUI interchange at US-131 and 44th Street in city of Wyoming, Kent County.
Department of Transportation

Interchange types

Different types of interchanges, such as single-point urban interchanges and diverging diamond interchanges, increase safety and mobility and reduce crashes. Learn more about these types of interchanges.

Single-Point Urban Interchange (SPUI)

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A single-point urban interchange (SPUI) is a type of highway interchange. In a SPUI (pronounced "Spooey"), a single traffic signal at the center of the interchange controls all left turns. Drivers make opposing left-turns at the same time under the protection of this signal.

Benefits

  • Constructed where there is not enough room for a standard interchange.
  • Ideal for urban areas.
  • Allows more vehicles to make a turn and clear the interchange in one traffic signal cycle.
  • Allows long, gradual turns so larger vehicles have more room to navigate the interchange.
  • It can be coordinated with cross-street signal systems.

Diverging Diamond Interchange (DDI)

A diverging diamond interchange in the Metro Detroit area.
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How to drive a DDI?

  • Follow signs: Following the signs, signals and pavement markings, motorists cross over to the left side after the first set of traffic signals.
  • Free flow left turns: All left turns onto the freeway are free flow, meaning vehicles do not have to stop to access the ramp.
  • Through-traffic: Vehicles going straight simply proceed through a second set of traffic signals and cross back to the right side of the road.