C&C Consulting Engineers was responsible for complete engineering services for the total replacement of this 500-foot, five-span bridge over Interstate-95. Recognized as a high priority by the Massachusetts Highway Department, the bridge had one of the lowest ratings in the Commonwealth and posed a significant hazard.
Due to the high traffic volumes at this location, it was determined that lane closures for traffic management were not permissible. Consequently, a one-mile, $2 million reversible median detour was designed that allowed traffic to remain unimpeded while individual spans of the bridge were removed and replaced with the new structure. Since the northbound and southbound mainline roadways were on a slight horizontal curvature, the geometrics of the x-shaped detour involved complex combinations of horizontal and vertical alignment, cross-slope, and super-elevation to ensure that the detour could be run in either direction at the same speed as the open highway.
Recognizing that the detours would be semi-permanent facilities meant to perform for a minimum of three years, C&C specified regular guardrail wherever possible, instead of the normal jersey barriers. This strategy helped to reduce the potential of injury-causing accidents. It also allowed easier snow removal during the winter months.
During the design phase, it was recognized that grass planted on the side-slopes remaining between the mainline and the detour would be difficult to mow because the areas would be inaccessible with standard tractor mowers, so a blanket of crushed stone was specified as the top course instead.