Should a 10' high truck be able to clear an 11' bridge?

Well either the 11' high bridge is less than 10' high or the truck is more than 11' high. Maybe the sign is wrong?

Was the height NGVD or NAVD?? :-/

That's a good point... The bridge is NGVD29 and the truck is NAVD88.:good: :good: :good:

The reefers I used to pull were 13'6" and most of us payed attention to close overhead structures, never know how many lifts have been placed since it was measured and marked, standing up with the door open, creeping along and watching the trailer, happened several times, never had to let any air out of the tires for clearance and never did have to back out, but some were close. Chacgo was the worst place for low clearances, a book with all the low overheads in the nation, indexed by city used to be available so you could plan your route to avoid those traps, Yep had one. Bet the height was marked long ago and the responsible party never upgraded the data. Lots of drivers out there who never pay attention because they have became so dependent on ODOT to do their thinking for them they fail to look for danger. Used to hear drivers sitting around bragging about what good drivers they were because of being able to drive their way out of a mess, I called it luck and knew that a good driver would avoid most of what they were braying about. Yes, I meant braying.
jud

The problem is . . .

that the trucks are over 50' long.

The bridges that I've seen hit are on hill grades with flat areas under the bridges.

The county engineer(?), must send a crew out to measure it and they measure from the road under the bridge, which is, in fact 11 feet high.

The problem is that a truck going down the road(hill), is supported by axles that are 30-40 feet apart.

While the first set of tires is under the bridge and the truck does in fact clear, as the truck moves forward the higher height of the rear axles come into play and effectively raises the roof of the truck until it meets(hits), the bridge.

The top of the truck might be 10' above the axles, but no always only 10' above the pavement between the axles.

Shouldn't this be considered when the county engineer(?), measures the height, then puts up a sign indicating the safe height?

Especially since the signs are really for the trucks in the first place.

Many bridge heights that are posted at a bridge were in place before the last few road surfaces were added.

And as Retired69 said, the measurement is at the lowest point on the vertical curve in the roadway and will not reflect the midpoint height of a trailer that is elevated.

Around here it is best to contact the DOT and let them be in charge of planning a safe route.

The saying in aviation is, "A superior pilot uses his superior judgment to avoid situations that would require the use of his superior skills."

Well sure it should.
Unless the roadway has been re-surfaced a few times and no one bothered to update bridge height.

The problem is . . .

I think that the driver should be the responsible party. The engineer has no way to know what all the possible vehicle lengths might arrive at the low clearance. The sign should show the measured height. As an occasional part time truck driver, I've been in situations where somebody had to watch, just to be safe. Ain't struck or been stuck yet, at least vertically.

There is a sign

in Griffin, Ga. (just south of Atlanta) that says:

"If you hit this sign you will hit that bridge".

Kinda smart if you ask me.

Andy

What I'm really asking is . . .

as a society, aren't we progressive enough to consider that since the purpose of a height sign is to protect a bridge, then why isn't this scenerio(the hill underpass), considered in the signage?

I don't think anyone really cares that drivers in cars know that the height is 10' or 11'.

The signs are obviously for truck traffic and to keep a truck from damaging a bridge. So why give truck drivers information that unreliable from the get-go?

What's particularly wrong with requiring the signage height to actually reflect what a typical truck, that uses the particular road, needs regarding height?

To me, it's been obvious that this is a real problem since I was about 6 or so years old. This is when a truck hit a bridge that "supposedly" had about 2' extra clearance and still got hit.

When my dad drove me down that same road, I immediately understood how it happened, and have always wondered, since then, why the signs didn't actually reflect the information needed for the traffic(trucks), that rely on them the most.

Now, in the days of computers, electronic drafting and number crunching out the proverbial wazoo . . . why doesn't the simple act of informing truck traffic that a 10' high truck will not clear an 11' or 12' high bridge seem important . . . even after trucks actually do hit these bridges? After all, this is the 21st century . . . isn't it?

It seems to me, to be just downright stupid and ignorant on the part of governing entities to not "want" . . . I mean to really, "really" want this information to be posted to more realistically protect bridges.

If you hit this sign . . .

a sign like this . . . before the bridge(which it would have to be, as a warning, would actually be even worse on a hill.

A truck on a hill, with a "flat" area under the bridge, that relied on a sign like this would clear the sign and clear the bridge . . . until, the front of the trailer is above the flat area under the bridge. That's when the rear tires, which are actually at a higher elevation, causes the top of the truck between the axles to effectively "rise", to meet the bridge.

This can only happen where the slope changes under the bridge, either because the area under the bridge is flat, then continues downslope on the other side, or worse yet, when the bridge is at the low spot between two inclines.

In either case, a sign, such as you mentioned would actually give a truck driver a sense of safety that just plainly doesn't exist.

Again . . . it all comes back to protecting of the bridge.

The problem is . . .

> The engineer has no way to know what all the possible vehicle lengths might arrive at the low clearance.
Engineers routinely use standardized truck weights, lengths and turning radii in roadway design. Nevertheless, I agree that final responsibility should be with the trucker.