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7 Mile Road Bridge

7 Mile Road Bridge

Primary Photographer(s): Nathan Holth

Bridge Documented: December 15, 2010

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Key Facts

Facility Carried / Feature Intersected
7 Mile Road Over Southfield Freeway (M-39)
Location
Detroit: Wayne County, Michigan: United States
Construction Date and Builder / Engineer
1963 By Builder/Contractor: Unknown and Engineer/Design: Michigan State Highway Department

Technical Facts

Rehabilitation Date
Not Available or Not Applicable
Main Span Length
53.8 Feet (16.4 Meters)
Structure Length
109 Feet (33.22 Meters)
Roadway Width
125 Feet (38.1 Meters)
Spans
2 Main Span(s)
NBI Number
82182193000S080

Historic Significance Rating (HSR)

Bridge Documentation

This bridge has been altered, resulting in complete, or nearly complete loss of historic significance!

View Archived National Bridge Inventory Report - Has Additional Details and Evaluation

This bridge had the railings which made it noteworthy removed and replaced in 2011!

Southfield Freeway Bridges

In describing the history of Michigan's Signature R4 Railings, it is essential to discuss bridges on the Southfield Freeway. In 2010, a small group of Southfield Freeway overpasses were the only known surviving examples in Michigan of bridges containing an unusual variation of the R4 railing design, in which a shorter version of the R4 railings were mounted on top of a concrete parapet. With the youngest bridge on the Southfield Freeway that has these railings having been built in 1964, this R4 and parapet railing design appears to have been the final railing design that Michigan used R4 style railing panels on. No examples of bridges newer than 1964 are currently known to have been built with R4 railings on them, suggesting that 1964 may have been the final year that R4 railings were used. The R4 and parapet design seen on the Southfield Freeway overpasses seems to be suggestive of the transition to a railing design that Michigan used extensively in the 1960s and 1970s, called the tube and parapet railing, where a pipe was mounted on top of a concrete parapet as seen on the Wadhams Bridge. According to MDOT, the tube and parapet railing was first used in 1961, so there apparently was a small overlap where R4 railings were still being used, but the R4 railings were also available for bridges as well. The R4 and parapet railings seen on the Southfield Freeway Bridges were apparently something that was not commonly used nor adopted as a commonly used bridge standard. The lack of additional examples elsewhere in the state as well as the labeling of the railings in original bridge plans as "special bridge railing parapet type" seem to suggest this.

The Southfield Freeway Bridges as featured on HistoricBridges.org are not themselves very noteworthy on a technological or historical significance basis. They are a common bridge type, and having been built in the early 1960s are not very old and they do not pre-date the Interstate Highway System. However, the railings they contain are historically significant as an essential piece in documenting Michigan's bridge railing history. For this reason, these bridges appear on HistoricBridges.org.

All of the Southfield Freeway Bridges that retain the R4 and parapet railings are to have their railings and decks removed and replaced with modern railings. In a couple cases, complete demolition of the bridges will occur. The railings which will replace the historic ones are an extremely common type of railing used on modern bridges in urban settings in Michigan. The railing might be described as the descendent of the R4 and parapet (and the 1960s/1970s tube and parapet) railing since it consists of a concrete parapet with metal tube on top. However the so-called "aesthetic parapet tube" railing is downright plain and ugly compared to the historic R4 and parapet railings on the bridges. Why is the new railing described as "aesthetic?" Simply because the railing has a few simple horizontal lines on the parapet and the use of a metal tube lowers the height of barrier which can not be seen through enhancing the view from the roadway. That such meager attentions to the appearance of a railing qualify as "aesthetic" in the modern transportation world shows just how far removed modern bridges are from the concept of a "beautiful bridge." The aesthetic parapet tube is shown in the drawing to the right, taken from MDOT bridge plan sheets for the Southfield Freeway project.

For the Southfield Freeway bridges, HistoricBridges.org would have suggested a compromise where the aesthetic parapet tube railing could be redesigned to hold the existing R4 railing panels on top instead of the default metal tube. This would have increased railing safety while retaining part of the historic railing, and would have allowed the bridges to remain unique from other Detroit area overpasses. Unfortunately, MDOT did not pursue a creative solution like that. The only good news is that the plans for the bridge projects do call for the salvage and storage of the R4 railing panels. It is presumed that these railing panels will be added to the stockpile of R4 railings that MDOT has stored for historic preservation and context sensitive bridge projects.

About This Bridge

This wide bridge is an example of how interchanges were designed on the Southfield Freeway. Offramps and onramps are arranged in a traditional depressed freeway diamond design. Upon reaching the road above, traffic exiting the freeway has the option of continuing in the direction of exit on the service road or turning onto the road that was exited at. Traffic can also turn onto a separate lane that is present at the two edges of the bridge deck which allows traffic to make a U-turn and continue on the service drive in the opposite direction from which traffic exited. These dedicated U-turn lanes are separated from the main road by small islands, and this design allows traffic to make a U-turn without having to enter the main road and having to deal with a signalized intersection.

A diagram from the original plans for this bridge is shown to the right which indicates the layout of the deck.

Information About This Bridge From MDOT Bridge Plans

The existing structure is a two span structure with an over all length of 108’-6" and a clear roadway of 75’-0" (thru lanes), 15’-0" (turn lanes). A concrete slab on continuous supported rolled beams is supported by spread footing abutments and pier. The bridge was built in 1962 and was designed for HS 20-16-44.

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