Basic Road Terminology

A draw bridge is a bridge that has a deck or double leaf bascule that lifts upward to allow for ships to pass by without overhead obstruction. An example is Interstate 280 over the Maumee River in Toledo, Ohio.

Any highway with a physical barrier (such as concrete barrier or landscaped median) that separates the two directions of traffic is known as a divided highway. Divided highways may have four or more lanes. Divided Highways is also the name of a book and PBS series from 1996 that provided a glimpse of the politics and history behind the development of the nation's highway system.

A route is considered decommissioned when signage for that route is removed from the roadway. Decommissioning normally occurs when a route is taken from state control and given to a local entity (city or county) to maintain or replaced with a new alignment using a different route number.

A controlled access roadway is one with access points only at interchanges or intersections. No private driveways or business entrances are permitted on controlled access roadways. These roads are often regarded as expressways, though controlled access arterials exist as well such as Maryland 24 in Harford County.

A collector distributor (c/d) roadway on a freeway handles entering and exiting traffic at a single interchange of through a group of adjacent interchanges. These lanes separate on and off-ramp movements from a freeway or expressway mainline to reduce motorist weaving on through traffic. C/d roadways are also often used at full cloverleaf interchanges, allowing them to remain in place due to the reduced weaving traffic.

The middle turning lanes found on busy arterials in urban areas or passing lanes that may be used by either direction of traffic. Sometimes these lanes are nicknamed as suicide lanes because both directions of traffic can use them. An example is along U.S. 287 in Wyoming just north of the Colorado State Line.

A route that connects the freeway or through highway with the downtown and commercial areas of a city or town are found along business routes. The business route is typically the original alignment of the highway before a freeway or bypass route was constructed. Interstate business routes are identified by green business loop or business spur shields. A business loop implies that the business route will return to the parent [...]

A beltway is a freeway that completely encircles a metropolitan area. Examples include Interstate 495 around Washington, D.C., and Interstate 465 around Indianapolis, Indiana. There are not as many full beltways west of the Mississippi River.

Auxiliary routes include alternate, business, bypass and truck routes from a numbered highway.