No more overheads on bridges per FHWA edict?

[jeffandnicole]

Would this be just for BGS's?  Or also for LGS's (e.g. the name of the road) and for clearance signs?

Just BGSs.  Bridge IDs, cross street nameplates and clearance signs are fine.

[roadfro]

Would the reason for the change be that sign gantries mounted on bridge sides tend to shorten the lives of the structures through stresses imposed by the weight of the signs, not to mention the moisture that invariably leaks past the mounting posts into the concrete itself?

In a nutshell, yes; at least from what I've been told.

I question this. Compared to the weight of an overpass, or even the weight of a vehicle, a sign is nothing. Especially if the sign was planned in the design of the bridge. And the moisture problem, while plausible, doesn't necessarily explain a ban on mounting signs to steel girder bridges.

[Pete from Boston]

Would the reason for the change be that sign gantries mounted on bridge sides tend to shorten the lives of the structures through stresses imposed by the weight of the signs, not to mention the moisture that invariably leaks past the mounting posts into the concrete itself?

In a nutshell, yes; at least from what I've been told.

I question this. Compared to the weight of an overpass, or even the weight of a vehicle, a sign is nothing. Especially if the sign was planned in the design of the bridge. And the moisture problem, while plausible, doesn't necessarily explain a ban on mounting signs to steel girder bridges.

Wasn't wind load mentioned somewhere upthread?

[cl94]

Would the reason for the change be that sign gantries mounted on bridge sides tend to shorten the lives of the structures through stresses imposed by the weight of the signs, not to mention the moisture that invariably leaks past the mounting posts into the concrete itself?

In a nutshell, yes; at least from what I've been told.

I question this. Compared to the weight of an overpass, or even the weight of a vehicle, a sign is nothing. Especially if the sign was planned in the design of the bridge. And the moisture problem, while plausible, doesn't necessarily explain a ban on mounting signs to steel girder bridges.

Wasn't wind load mentioned somewhere upthread?

Wind load could go either way. Depending on where you are or the size of the sign, it might be more efficient to place a sign on a bridge because the wind load on the sign would result in an unnecessarily extravagant system of reinforcement. A lot of the wind load is blocked by the bridge substructure (which would receive it anyway), but several signs could have an effect. In reality, if a sign is less than 2 feet taller than the bridge substructure, deck, and railings, the wind load contributed by a sign will be relatively negligible.

[cpzilliacus]

Happened to be out on I-66 in Fairfax County, Virginia over the weekend, and noticed that bridge-mounted BGS panels on the Va. 243 (Nutley Street) overpass at the Vienna Metrorail station have been replaced by new ones mounted on structures just prior to the bridge.

[dcbjms]

Certainly explains what happened during the I-195 relocation project (aka the I-way - who in RIDOT came up with that lame name?  ), where a lot of the signage in downtown Providence got changed.  Fortunately there is still some remaining elsewhere.