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.
Some of the overpasses on the Southfield Freeway are steel stringer bridges, while others are pre-stressed concrete stringer bridges. This bridge is an example of a pre-stressed concrete bridge. When this bridge was built, the Michigan State Highway Department had just begun to use pre-stressed concrete in its bridges. By the 1960s when this bridge was built, this was not an experimental usage of the material however, but rather an indication that the experimentation was over and it was decided to be an effective bridge material. Although steel stringer continued to be built, just like on the Southfield Freeway, pre-stressed concrete became increasingly popular as a bridge material beginning in the 1960s and continuing to the present day.
This bridge has its plaque mounted on a concrete parapet that flanks the ends of the bridge. This is unusual since most of the bridges on this freeway have plaques mounted on the abutment walls under the bridges.
It is worth noting that although all of the historic aspects are being destroyed, a number of the overpasses on the Southfield Freeway are not being completely demolished, with the superstructure being rehabilitated instead. However among the bridges documented by HistoricBridges.org, a couple bridges, including this one, were selected for full demolition and replacement. Both were pre-stressed concrete bridges. Only one of the pre-stressed concrete bridges documented was to be rehabilitated. The remaining rehabilitated bridges were all steel stringers. These facts confirm HistoricBridges.org's suspicions that pre-stressed concrete may not be as reliable as is often thought. Some agencies like to claim that a new pre-stressed concrete bridge will last 100 years. However, bridges like this one seem to suggest that pre-stressed concrete may be more like a 50 year material.
Information About This Bridge From MDOT Bridge Plans
Type II AASHTO prestressed concrete i-beam structure built in 1960 consisting of 2 spans. The clear roadway width is 44'-0" and the bridge length is 104'-0".
This historic bridge has been demolished. This map is shown for reference purposes only.
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