|Inner Belt Expressway|
|Auxiliary route of I-70|
|Maintained by MoDOT|
|Length||11.17 mi (17.98 km)|
|South end||I-64 / US 40 in Richmond Heights|
|I-70 in Berkeley|
|North end||I-270 in Hazelwood|
Interstate 170 (I-170), also known as the Inner Belt Expressway, is an 11.17-mile (17.98 km) north–south auxiliary Interstate Highway in Greater St. Louis, Missouri. I-170 connects to I-270 at its northern terminus and I-64 at its southern terminus. I-170 crosses its parent, I-70, near St. Louis Lambert International Airport.
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I-170 was originally intended to provide an inner beltway within I-270 through St. Louis County extending to I-55 in the southern part of the county, commonly called South County; however, the portion of the route south of I-64/US Route 40 (US 40) was canceled due to local opposition. The portion of MetroLink's Cross County Extension south of I-64 runs roughly along the proposed alignment.
The southern portion of I-170 was built using St. Louis County funds in the 1960s through a shallow valley. It was signed as Route 725.
The southern two interchanges on I-170 (at I-64/US 40 and Galleria Parkway) were reconstructed as part of the first phase of the New I-64 project. Most notably, the new interchange includes direct access to I-170 from eastbound I-64; however, access to Galleria Parkway from northbound I-170 was eliminated. Eager Road access to and from I-170 was also revised in the New I-64 project.
Because I-170 terminates at I-64/US 40, a direct access from I-170 and I-64 (US 40) to I-55, I-270, and I-44 are lacked. Also, towns such as Richmond Heights, Brentwood, Maplewood, and Marlbourough lack access to the Interstates, St. Louis Lambert International Airport, South County, and to each other. Because of this, commuters either have to take indirect surface streets as bypasses, such as Hanley Road or River Des Peres Boulevard, which would result in a much higher mileage and time due to traffic signals and a longer route. This also results in higher traffic in residential streets and towns such as Shrewsbury. Proposals had been made to solve this problem, such as a new freeway for faster commute or "South County Connector" to connect Richmond Heights to South County, but these proposals had been postponed due to lack of funding.
The entire route is in St. Louis County.
|Richmond Heights||0.00||0.00||1||I-64 / US 40 / Lewis and Clark Trail – Wentzville, St. Louis||Signed as exits 1A (east) and 1B (west)|
|0.438||0.705||1C||Brentwood Boulevard north / Eager Road||Southbound exit and northbound entrance|
|Clayton||0.809||1.302||1D||Brentwood Boulevard south||Southbound exit and northbound entrance (via Galleria Parkway)|
|1.170||1.883||1E||Forest Park Parkway east||Western terminus of the Forest Park Parkway|
|University City||2.374||3.821||2||Delmar Boulevard|
|Olivette||3.336||5.369||3||Route 340 (Olive Boulevard)|
|Overland||4.325||6.960||4||Route D (Page Avenue)|
|St. John||5.865||9.439||5||Route 180 (St. Charles Rock Road)|
|Bel-Ridge||7.027||11.309||6||Route 115 (Natural Bridge Road) – Cargo City||Access to the University of Missouri-St. Louis|
|Berkeley||7.654||12.318||7||I-70 – St. Louis, Kansas City||Signed as exit 7A (east) and 7B (west); exit 235|
|7.771||12.506||7C||Lambert–St. Louis International Airport||Southbound exit is via exit 7B|
|8.577||13.803||8||Scudder Road / North Hanley Road||No northbound entrance|
|9.167||14.753||9A||Airport Road – Cargo City|
|9.236||14.864||9B||Boeing||Northbound exit and southbound entrance|
|9.780||15.739||9C||North Hanley Road||Northbound exit and southbound entrance|
|10||I-270 – Kansas City, Chicago||Signed as exits 10A (west) and 10B (east)|
|1.000 mi = 1.609 km; 1.000 km = 0.621 mi|
- ^ Starks, Edward (January 27, 2022). "Table 2: Auxiliary Routes of the Dwight D. Eisenhower National System of Interstate and Defense Highways". FHWA Route Log and Finder List. Federal Highway Administration. Retrieved February 22, 2023.
- ^ Sutin, Phil; Hopgood, Mei-Ling (January 9, 1997). "Hundreds of Homes Face Razing for New Highway". St. Louis Post-Dispatch.
- ^ Sutin, Phil (March 14, 1997). "Westfall Sours On Extension of Interstate 170". St. Louis Post-Dispatch.
- ^ "Project Overview". The New I-64. Missouri Department of Transportation. Archived from the original on May 4, 2007. Retrieved May 28, 2007.
- ^ Leiser, Ken. "Linking South County, Clayton studied". St. Louis Post-Dispatch. Retrieved January 19, 2018.
- ^ "South County Connector: 1st Phase of 170 South Extension?". FOX2now.com. May 14, 2013. Retrieved January 14, 2018.
- ^ Missouri Department of Transportation (March 18, 2015). MoDOT HPMAPS (Map). Missouri Department of Transportation. Retrieved March 18, 2015.