Frequently Asked Questions

Why is there no I-50?

Interstate 50 and Interstate 60 were not assigned so as to avoid conflicts with U.S. 50 and U.S. 60 in the central part of the country.

Why are some routes unsigned?

Unsigned Interstates are generally not posted in an effort to not confuse or overburden motorists with an additional number on an already signed route. This is the case with not signing Interstate 595 in Maryland due to well established status of U.S. 50 along the same stretch of freeway. Interstate 124 and I-296 were previously posted, but later transitioned into unsigned routes due to overlaps with much longer U.S. Highways.

Why are there gaps?

Gaps were the result of incomplete sections of the Interstate Highway System, usually due to protest from area residents, environmental concerns, or costs. The most notable gap was along Interstate 95 between Mercer County and New Brunswick, New Jersey. This was due to the unbuilt Somerset Freeway, which was cancelled due to a combination of community, environmental and cost concerns. The gap was finally filled in 2018, when the two ramps opened at the I-95/Pennsylvania Turnpike Interchange in Bristol Township, Pennsylvania. This coincided with a realignment of I-95 east along the Turnpike and Pearl Harbor Memorial Turnpike Extension in New Jersey to the continuation of I-95 along the New Jersey Turnpike mainline.

Why do some routes end abruptly?

Similar to why there were gaps in the Interstate System, some routes end abruptly again due to community protest, potential damage to sensitive environmental areas such as wetlands, costs, and other major issues. The south end of Interstate 83 in Baltimore is an example, where the eastern leg connecting I-83 with I-95 was dropped due to major condemnation of property through the Fells Point area and other residential neighborhoods.

Why do Hawaii Interstates exist?

While obviously not connected to the rest of the Interstate Highway System, Hawaii Interstates, and those in Alaska and Puerto Rico exist for funding purposes. However, Interstates in Hawaii are fully signed, whereas the other two systems are not.

Why are business routes different?

Business Routes do not adhere to Interstate Highway Standards. They can be at-grade arterials, expressways, or follow city streets. These are generally state-maintained roadways, though there are instances where business routes are also locally signed and maintained.

Suspension Bridges

Cable Stay Bridges

Tied Arch Bridges

Steel Through Arch Bridges

Drawbridges

Tunnels

The Beavertail Tunnel, in De Beque Canyon, is the first of five eastbound tunnels along Interstate 70 across the state of Colorado. 08/10/16

Underground Tunnels

Tunnels Underwater

Tolled Interstates

At-Grade Intersections and Traffic Signals

Updated June 17, 2026