Free-flow interchange

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A free-flow interchange is an interchange in which all roads are grade-separated, and where movement from one road to another does not require the driver to stop for traffic (for example, the interchange may not include traffic lights or unsignalized at-grade intersections). Free-flow interchanges are less likely to induce traffic congestion than non-free-flow, but are typically more expensive both in money and in land.

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Some free-flow interchanges bring additional problems such as weaving or passing lane/fast lane exits (i.e. left exits in areas with right-hand traffic, and vice versa) that may be necessary to avoid additional costs, but lead to congestion and accidents and ultimately to an upgrade to another type of interchange.

A free flow interchange design, called double crossover merging interchange (DCMI), has received a patent. [1] The DCMI includes elements from the diverging diamond interchange (DDI) and the standard diamond interchange. It eliminates the disadvantages of weaving and of merging into the outside lane from which the standard DDI variation suffers.

Examples of free-flow interchanges

Examples of interchanges that are not free-flow

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Cloverleaf interchange

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Grade separation Type of road junction

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Diamond interchange Common type of road junction

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Single-point urban interchange Highway interchange design

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Diverging diamond interchange Freeway interchange design

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Terminology related to road transport—the transport of passengers or goods on paved routes between places—is diverse, with variation between dialects of English. There may also be regional differences within a single country, and some terms differ based on the side of the road traffic drives on. This glossary is an alphabetical listing of road transport terms.

References

  1. "United States Patent 8,950,970: Double Crossover Merging Interchange". United States Patent and Trademark Office. February 10, 2015. Retrieved August 4, 2015.