It happens quite occasionally on some of my long rides which makes it annoying, sometimes I have carried on regardlesly and found that I can pass the problem even if I have to walk but sometimes I cannot, especially if it is a bridge thats being replaced etc, then I blame my stupidity for carrying on.
An occasion which really bugged me last year, was on my route, I came across a sign which mentioned a road which was closed due to bridge repairs which was on my route, follow diversion signs, which I did and they also took me down my route so I presumed there must be an alternate way. After about 6 miles following the arrows, I eventually came to a sign saying, road closed ahead, end of diversion, and then it sunk in, in front of me was a dismantled bridge and the diversion signs had been for traffic crossing from the other side to get to the houses which was on my side of the river and I had followed those signs unknowingly. Was I fuming, with having to backtrack and get round this bridge it added on about another 15 miles.
Another of my pet hates is when your driving or cycling in a strange town and your confronted with for example, "Bridge Street closed, use High Street via Market Square" and as a stranger, I do not have the foggiest where these places are and if they are on my route and if so where the hell do I find the places mentioned for the alternative.
I have done searches online looking for a local council website's etc for road closures, especcially regarding small country road, but it only seems to be A roads and motorways that get a mention. One small country lane I do use a lot for my long rides is a "gateway" to many places was closed for almost 3 months this year for resurfacing, but the only way to find out if it had been reopened was ride there and chance it, it caught me out about 5 times in the end. I have a feeling they had dug it all up and relaid it for that period of time.
An occasion which really bugged me last year, was on my route, I came across a sign which mentioned a road which was closed due to bridge repairs which was on my route, follow diversion signs, which I did and they also took me down my route so I presumed there must be an alternate way. After about 6 miles following the arrows, I eventually came to a sign saying, road closed ahead, end of diversion, and then it sunk in, in front of me was a dismantled bridge and the diversion signs had been for traffic crossing from the other side to get to the houses which was on my side of the river and I had followed those signs unknowingly. Was I fuming, with having to backtrack and get round this bridge it added on about another 15 miles.
Another of my pet hates is when your driving or cycling in a strange town and your confronted with for example, "Bridge Street closed, use High Street via Market Square" and as a stranger, I do not have the foggiest where these places are and if they are on my route and if so where the hell do I find the places mentioned for the alternative.
I have done searches online looking for a local council website's etc for road closures, especcially regarding small country road, but it only seems to be A roads and motorways that get a mention. One small country lane I do use a lot for my long rides is a "gateway" to many places was closed for almost 3 months this year for resurfacing, but the only way to find out if it had been reopened was ride there and chance it, it caught me out about 5 times in the end. I have a feeling they had dug it all up and relaid it for that period of time.

Further west on NCN 76, the foot bridge over the busy A876 which quickly becomes the M876 has been shut for months (I know detours but none are signed)