On April 5, 1987, a Thruway bridge over Schoharie Creek collapsed, killing several motorists. While this bridge was replaced, traffic was initially forced to leave the Thruway at Exit 27 (Amsterdam), follow NY 5S and re-enter the Thruway at Exit 28. (Or vice-versa depending on the direction of travel). To this day, along NY 5S are a couple of Thruway and I-90 trailblazers without the "TO" over them.
A detour was construced and opened on June 29, 1987 while the collapsed bridge was rebuilt. Traffic was reduced to one lane in each direction and diverted to a temporary road that ran to the north of the Thruway. This roadway went down a hill onto NY 5S, used the existing NY 5S bridge to cross over Schoharie Creek and then back up the hill and reconnected to the Thruway. NY 5S on the other hand, took over an adjacent railroad bridge. This bridge has since been converted to a recreational bike and foot path. Black tarps were placed on the southern side of the NY 5S bridge that the Thruway was using, essentially "hiding" the remains of the collapsed bridge and the construction of the new bridge. Also, black-on-orange mileposts were placed along the temporary roadway with a "D" designation... (mile D-1, mile D-2). The detour roadway was used until December 9, 1987. Eastbound traffic was moved off on December 7 and then westbound traffic was moved off on December 9 (with both drections using the southern portion of the new bridge). The new Thruway bridge was completed on May 21, 1988.
Below are a couple of pictures of what remains of that temporary roadway. The first picture is standing about 1/2 mile from the eastern end of it, where it left the Thruway. These pictures were taken in the summer of 1997.