Two alternatives we used this summer in NY and MA were:
Google earth the "obstruction". In many of the pictures, you will see an 18 wheeler going through. If he can go, I can go.
From Google earth, scroll from the obstruction until you see a business that likely has 18 wheeler deliveries/does road work, etc.
This summer's lowest bridge clearance (on paper) that we wanted to go under was less than 2 blocks from a NY DOT office. Took 10 seconds on the phone for him to tell me the exact clearance and assure me that Walmart trucks went under it all the time. So, we did not detour around it.