I-675 highlighted in red
|Auxiliary route of I-75|
|Maintained by MDOT|
|Length||7.728 mi  (12.437 km)|
|Existed||October 21, 1971–present|
|South end||I-75 / US 23 near Saginaw|
|M-58 in Saginaw|
|North end||I-75 / US 23 in Zilwaukee|
Interstate 675 (I-675) is an auxiliary Interstate Highway in the US state of Michigan. The freeway is a 7.7-mile-long (12.4 km) loop route through downtown Saginaw, as I-75 passes on the east side of the city. I-675 is also a state trunkline highway that provided a bypass of the former drawbridge carrying I-75 and US Highway 23 (US 23) across the Saginaw River. Construction of I-675 started in 1969 and the freeway opened in 1971. Since then, sections near downtown were reconstructed from 2009 through 2011 to update one of the freeway's interchanges and rebuild the bridge over the Saginaw River.
Splitting from I-75/US 23 on the eastern side of Saginaw, I-675 turns west toward downtown. The freeway runs between residential neighborhoods and has an interchange with Veterans Memorial Parkway. West of that interchange,   it crosses a line of the Huron and Eastern Railway.  From there, it runs on the northern edge of downtown near the Dow Event Center, spanning the Saginaw River on the Henry G. Marsh Bridge. On the west side of the river, the trunkline meets an interchange with M-58. From there it turns northward,   crossing a line of the Mid-Michigan Railroad.  I-675 continues northward, passing to the east of the Aleda E. Lutz VA Medical Center and through more residential neighborhoods in Saginaw Township North. After the interchange with Tittabawassee Road, which provides access to the Fashion Square Mall, I-675 turns northeasterly to connect back to I-75/US 23 north of the Zilwaukee Bridge.   The entire length of the freeway has four lanes (two in each direction). 
Like other state highways in Michigan, I-675 is maintained by the Michigan Department of Transportation (MDOT). In 2015, the department's traffic surveys showed that on average, 31,300 vehicles used the freeway daily across the river and 9,400 vehicles did so each day north of Tittabawassee Road, the highest and lowest counts along the trunkline, respectively.  As an Interstate Highway, all of I-675 is listed on the National Highway System,  a network of roads important to the country's economy, defense, and mobility. 
I-675 was initially planned in the mid-1950s,  and the Michigan State Highway Department (MSHD) originally proposed the number I-275 for the freeway through Saginaw in 1958, while the MSHD proposed an I-73 number for what is now I-275.  The state started construction on I-675 in 1969.   The freeway was to provide access to the downtown Saginaw area and serve as a bypass for the original Zilwaukee Bridge northeast of downtown, roles that continue today. At the time, the Zilwaukee Bridge was a bascule bridge that could be raised to allow shipping traffic to use the Saginaw River. Opening the drawbridge would back traffic up on the freeway for up to four hours on holiday weekends. I-675 helped relieve the congestion during such times.  The record was a 56-mile-long (90 km) traffic jam on Labor Day 1968, although 20-mile (32 km) backups were common until the shipping companies using the Saginaw River limited their traffic in 1970.  The freeway was completed in 1971 and opened to traffic that year.   After completion, the state considered reconstructing I-675 to make the downtown freeway the through routing for I-75/US 23 in the Saginaw area to bypass the bascule bridge.  Originally to be completed in 1983, the replacement bridge on I-75/US 23 finally opened on September 19, 1988.  The next year, southbound I-675 was used to divert traffic around a temporary closure on the southbound span of the Zilwaukee Bridge. At the same time, northbound I-675 was closed while crews replaced the deck on the bridge over the Saginaw River. 
In 2002, the Zilwaukee Bridge was closed for a few months for joint repair work, and traffic was diverted onto I-675.  The freeway through downtown was pressed back into service as a detour around the Zilwaukee Bridge for six months in 2008 as a mishap involving several steel reinforcement rods during a maintenance project closed that structure for an extended period of time.  Then, starting in May 2009 and ending in November 2011, sections of I-675 were closed from exit 2 easterly to begin renovations during the summer construction seasons. These projects included rehabilitation of the Henry Marsh Bridge, the reconstruction of overpasses, and a redesigned exit at Warren Avenue to ease access into downtown Saginaw.   The project cost $42 million (equivalent to $46.2 million in 2016 ). 
The entire highway is in Saginaw County.
|Buena Vista Township||0.000||0.000||—||I-75 / US 23 – Flint, Mackinac Bridge||Exit 150 on I-75/US 23|
|1||Veterans Memorial Parkway|
|2A||5th Avenue, 6th Avenue||Northbound exit and southbound entrance|
|2.333||3.755||2B||To M-13 / Warren Avenue, Jefferson Avenue – Downtown Saginaw||Signed as exit 2 southbound; Warren Avenue signed northbound only, Jefferson Avenue signed southbound only|
|3||M-58 (Davenport Avenue) / Michigan Avenue||Southbound exit via Hill Street; eastern terminus of M-58|
|Saginaw Township||5.854||9.421||6||Tittabawassee Road – Zilwaukee|
|Zilwaukee Township||7.728||12.437||—||I-75 / US 23 – Flint, Mackinac Bridge||Exit 155 on I-75/US 23|
|1.000 mi = 1.609 km; 1.000 km = 0.621 mi|
- "Highway Loop Completed". The Times Herald. Port Huron, MI. Associated Press. p. 23. OCLC 36177739. Retrieved March 1, 2017 – via Newspapers.com.
- Michigan Department of Transportation & Michigan Center for Shared Solutions and Technology Partnerships (2009). MDOT Physical Reference Finder Application (Map). Michigan Department of Transportation. Retrieved May 15, 2012.
- Michigan Department of Transportation (2012). Pure Michigan: State Transportation Map (Map). c. 1:221,760. Lansing: Michigan Department of Transportation. Saginaw inset. OCLC 42778335, 794857350.
- Google (July 12, 2012). "Overview Map of I-675" (Map). Google Maps. Google. Retrieved July 12, 2012.
- Michigan Department of Transportation (January 2011). Michigan's Railroad System (PDF) (Map). Scale not given. Lansing: Michigan Department of Transportation. Archived from the original (PDF) on September 21, 2012. Retrieved February 1, 2011.
- Bureau of Transportation Planning (2015). "Traffic Monitoring Information System". Michigan Department of Transportation. Retrieved January 28, 2017.
- Michigan Department of Transportation (April 23, 2006). National Highway System, Michigan (PDF) (Map). Scale not given. Lansing: Michigan Department of Transportation. Archived from the original (PDF) on September 21, 2012. Retrieved October 7, 2008.
- Natzke, Stefan; Neathery, Mike & Adderly, Kevin (June 20, 2012). "What is the National Highway System?". National Highway System. Federal Highway Administration. Retrieved July 1, 2012.
- Bureau of Public Roads (1955). "Saginaw" (Map). General Location of National System of Interstate Highways Including All Additional Routes at Urban Areas Designated in September 1955. Scale not given. Washington, DC: Government Printing Office. p. 46. OCLC 4165975. Retrieved September 18, 2016 – via Wikimedia Commons.
- Michigan State Highway Department (April 25, 1958). "Recommended Interstate Route Numbering for Michigan". Lansing: Michigan State Highway Department. Archived from the original on August 5, 2004.
- Michigan Department of State Highways & H.M. Gousha (1969). Michigan, Great Lake State: Official Highway Map (Map). c. 1:918,720. Lansing: Michigan Department of State Highways. § J12. OCLC 12701120. Retrieved August 12, 2017 – via Archives of Michigan.
- Michigan Department of State Highways (1970). Michigan, Great Lake State: Official Highway Map (Map). c. 1:918,720. Lansing: Michigan Department of State Highways. § J12. OCLC 12701120.
- Hyde, Charles K. (1993). Historic Highway Bridges of Michigan. Detroit: Wayne State University Press. pp. 166–8. ISBN 0-8143-2448-7. OCLC 27011079.
- Benac, Nancy (July 27, 1981). "Drawbridge to Be Traded for Huge Span at Zilwaukee". The Argus-Press. Owosso, MI. Associated Press. p. 2. Retrieved September 18, 2016 – via Google News.
- Burns, Gus (June 30, 2011). "Saginaw Interstate 675 Work: 1,000 Truckloads of Fill Sand, $14.4 million". The Saginaw News. Archived from the original on July 12, 2012. Retrieved July 12, 2012.
- Michigan Department of Transportation (1987). "Section 2: Background". The Zilwaukee Bridge: From the Beginning. Lansing: Michigan Department of Transportation. OCLC 16106385. Retrieved September 18, 2016 – via Michigan Highways.
- Staff writer (September 19, 1988). "Zilwaukee Bridge Now Open North, South—Partly". The Blade. Toledo, OH. p. 1. OCLC 12962717. Retrieved July 12, 2012 – via Google News.
- Gillmore, Dan (July 17, 1989). "Construction Closes Lanes on I-75, Bridge". Detroit Free Press. p. 3. ISSN 1055-2758. OCLC 474189830. Retrieved March 1, 2017 – via Newspapers.com.
- Leach, Hugh (March 4, 2002). "Projects Affect Jackson Route". Lansing State Journal. p. 9. OCLC 61312043. Retrieved March 1, 2017 – via Newspapers.com.
- Barber, Barrie (November 28, 2010). "Two Years Later, MDOT Still Investigating Zilwaukee Bridge Maintenance Mishap that Closed Span for Months". The Saginaw News. Archived from the original on January 29, 2013. Retrieved September 18, 2016.
- Henson, Stacey (May 26, 2009). "Interstate 675 Closures Begin Today in Saginaw County". The Saginaw News. Archived from the original on July 12, 2012. Retrieved October 10, 2011.
- Barber, Barrie (November 2, 2011). "MDOT Now Says I-675 Will Reopen Mid-Day". The Saginaw News. Archived from the original on July 12, 2012. Retrieved July 12, 2012.
- Thomas, Ryland & Williamson, Samuel H. (2018). "What Was the U.S. GDP Then?". MeasuringWorth. Retrieved January 5, 2018. United States Gross Domestic Product deflator figures follow the Measuring Worth series.
- "County with Worst Bridges to Get Fixes: Saginaw in Line for Two-Year, $42 Million Repair on I-675". The Times Herald. Port Huron, MI. p. 3. OCLC 36177739. Retrieved March 1, 2017 – via Newspapers.com.
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