page_title: List of gaps in Interstate Highways
section_title: Undivided and narrow freeways
hierarchical_section_title: List of gaps in Interstate Highways / Freeway gaps / Undivided and narrow freeways
caption_attribution_description: English: Interstate 93/US Route 3 in Franconia Notch
context_page_description: There are gaps in the Interstate Highway system, where the roadway carrying an Interstate shield does not conform to the standards set by the Federal Highway Administration, the body that sets the regulations for the Interstate Highway System. For the most part, the Interstate Highway System in the United States is a connected system, with most freeways completed; however, some Interstates still have gaps. These gaps can be due to unconnected segments of the same route or from failure of the road to fully conform to Interstate standards by including such characteristics as at-grade crossings, traffic lights, undivided or narrow freeways, or movable bridges.
context_section_description: This section addresses two-lane freeways and other narrow or undivided freeway sections of the Interstate, excepting instances of continuing routes using one-lane ramps and merge leads. Narrow gaps between opposing directions with jersey barriers taller than four feet (1.2 m) are excluded from this section; therefore the separation criterion is really either a 4-foot-tall (1.2 m) wall, or a 100-foot-wide (30 m) median, whichever is greater.
  I-40's western 15 miles (24 km) in North Carolina in the Harmon Den Wildlife Management Area has several S-curves, a Jersey barrier with extremely narrow left shoulders and a few at-grade intersections albeit in RIRO style.
  I-55 enters Tennessee from Arkansas on the Memphis and Arkansas Bridge, which in itself would merit mention as a narrow through truss bridge. Just east of the bridge I-55 transitions from its east–west river crossing to the north–south alignment heading toward Jackson, Mississippi. There is an interchange that forces through I-55 traffic to enter and exit in an old cloverleaf; improvements are planned but are stalled.  The improvements to the I-55 / Crump Boulevard interchange will be accomplished by constructing new through travel lanes for mainline I-55 traffic, which will eliminate the requirement for interstate traffic to use single-lane, low-speed ramps in order to continue on I-55. A new multi-lane roundabout intersection will be constructed to replace the existing cloverleaf interchange and provide improved access to and from I-55 and existing local roadways.
  Interstate 70 is one-lane only for these following reasons:
  Interstate 70 in Kansas has only one lane for eastbound through traffic for several hundred feet in Kansas City where the highway approaches the Lewis and Clark Viaduct Bridge, which carries the highway over the Kansas River toward Kansas City, Missouri. Interstate 670, just a few blocks south provides an alternate route without this bottleneck.
  Interstate 70 in West Virginia has only one lane for approximately one thousand feet in Wheeling, where the highway enters the Wheeling Tunnel and crosses the Ohio River on the Fort Henry Bridge. Nearby I-470 provides relief from this situation.
  The Mackinac Bridge, which carries I-75 over the Straits of Mackinac between St. Ignace and Mackinaw City, Michigan, has no wide median or hard shoulders due to space constraints. Nor does it have a Jersey barrier; instead, it has either a 4-inch-tall (10 cm) yellow divider between the opposing directions (where the inner lanes are a metal grate) or a flat double-yellow line (where the inner lanes are paved). The speed limit is also reduced to 45 mph (70 km/h) for cars and 20 mph (30 km/h) for trucks.  The highway returns to Interstate standard for about 50 miles until it reaches the Sault Ste. Marie International Bridge, which carries undivided lanes to the Canada–US border in the middle of the bridge, where I-75 terminates.
  The Thousand Islands Bridge, which carries I-81 over part of the Saint Lawrence River, is an undivided two-lane road.
  I-93 is a two-lane divided parkway, or a "super two", through Franconia Notch in New Hampshire. A four-lane Interstate Highway was once proposed here, but the concept was abandoned because of environmental concerns, in part because of vibrations that could harm the Old Man of the Mountain rock formation (which collapsed in 2003 regardless). This section of highway was for many years marked as US 3 and "To I-93", but these have now been replaced with regular I-93 signs. The Federal Highway Act of 1973 exempts this 7.6-mile (12.2 km) stretch from the Interstate Highway standards that apply elsewhere, and this highway is considered to be I-93 for all practical purposes. This section of I-93 in New Hampshire is now the only remaining multi-mile section of two-lane freeway on an Interstate Highway in the United States. In addition, parking along portions of I-93 through Franconia Notch was permitted until early 2019 when barriers and signage were posted due to safety concerns.
  Some stretches of Interstate highway use a barrier tr
caption: Two-lane stretch of I-93 through Franconia Notch in New Hampshire
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