Why were early interstate bridges built so low?

[Rothman]

Used to be no trucks but at some point trucks that are low enough to fit under the bridges were allowed.

by trucks i mean tractor-trailers.

Hell, 53' trucks are banned on everything in New York City other than I-95, the Clearview, the LIE east of the Clearview, the Van Wyck, and Sunrise Highway.

Oh...yeah umm about that. They just turn a blind eye to it. As most trailers are 53 foot now.

Yeah, I've seen a couple of 53-footers on Manhattan the last couple of times I was down there.

[SteveG1988]

If a trailer isn't dedicated to NY it doesn't pay to have it be a 48 footer.

[Sykotyk]

NYC has a 55 foot overall length limit as well. But, any vehicle recognized as under STAA (interstate commerce) has normal restrictions to the National Network and travel to and from the network. There's 53' trailers all over NYC whenever I'm there. Many even parking on the streets around Major Deegan near the Cross Bronx, and along I-95 near the bus terminal.

The truck restriction is solely for domiciled trucks to NY state in and out of the city or strictly within NYC.

[froggie]

Regarding overhead bridge clearances, the Interregional Highways report of 1944 recommended 14ft, which according to the few references I've seen was carried into the early Interstate construction of the late 1950s.  Current standard (dated 2005 from AASHTO) is 16ft.

Regarding the comment on bridge shoulders, full-width shoulders (generally 10ft outside and 4ft inside) were not required until the 1967 Highway Act.  And on longer bridges (200ft or longer), a narrower shoulder can be allowed as long as it's no less than 4ft.

[D-Dey65]

Used to be no trucks but at some point trucks that are low enough to fit under the bridges were allowed.

by trucks i mean tractor-trailers.

Hell, 53' trucks are banned on everything in New York City other than I-95, the Clearview, the LIE east of the Clearview, the Van Wyck, and Sunrise Highway.

Hmm, I don't see it on Sunrise:

http://www.nyc.gov/html/dot/downloads/pdf/2015-06-08-truck-map-combined.pdf

Somehow though I imagined if they had actually completed the Clearview they wouldn't restrict them south of the LIE.

NYC has a 55 foot overall length limit as well. But, any vehicle recognized as under STAA (interstate commerce) has normal restrictions to the National Network and travel to and from the network. There's 53' trailers all over NYC whenever I'm there. Many even parking on the streets around Major Deegan near the Cross Bronx, and along I-95 near the bus terminal.

Well, the terminal is above I-95. If they have to make deliveries nearby, so be it.

[jwolfer]

When i was a kid every overpass had clearace listed like it was a requirement.  Now none do

LGMS428

[D-Dey65]

When i was a kid every overpass had clearace listed like it was a requirement.  Now none do

LGMS428

Really? Because I find that a lot of them have clearances listed that you wouldn't think are necessary. On the other hand, I just found out that the former Atlanta and West Point Railroad bridge over US 29 in Grantville, Georgia is 14'9" (higher than I thought), and the info about this is some barely visible stenciling on one side of that gray bridge. They need some normal MUTCD signage there.

[sparker]

When i was a kid every overpass had clearace listed like it was a requirement.  Now none do

LGMS428

Bridges with clearances below 16' are generally posted on CA state highways; this extends to the streets passing under freeways.  Some county/local roads are posted similarly as well -- some jurisdictions are more thorough than others.

[NJRoadfan]

NJ has its fare share of "scrapper" bridges on non-interstates. https://goo.gl/maps/v3N3aUQHJCE2

There don't seem to be too many examples on Interstates. Surprising, given the urban nature and age of most of the roads. NJ seems to sign any heights below 14.5 feet. Clearances on Interstate overpasses are generally low on only the rightmost lane. Some overpasses go slightly below 14ft in those cases.

[triplemultiplex]

Since we have some overlap with railfans here at AARoads, they might know if this hypothesis is at all plausible:
Those early, lower overpass clearances seem close to a standard vertical clearance for the railroads at the time.  I don't know what height the railroads were using at the time, in the days before double-stack container freight, but it seems similar.  Perhaps they used that as a baseline initially?
The thinking was probably, "Well if a rail car can fit under it, that should handle any truck out there, right?"

[Beltway]

jeffandnicole and I had this exchange on the thread on the Northeast board about speed limits in Pennsylvania increasing to 70 mph...

The bridge over I-78 at exit 16 [Midway Road] in Bethel, PA was 13' 11" in August 2012 per GSV.  I stayed at the Comfort Inn at that exit a couple of nights in the summer of 2010 and had "fun" watching the semis barely clear the overpass.  I would not want have been atop a semi trailer, even laying down.  This would've been a perfect place for an overhead "If you hit that sign, you will hit that bridge" sign.

ixnay

Since the legal height is 13' 6" and every truck would be built not to exceed that height, there should be no reason why that bridge would get hit.

Well...

...the overpass at Exit 17 (PA 419) also has a 13'11" clearance, and at Exit 19 (PA 183) there is a 13'10" clearance per GSV in August 2013*.

The Exit 16, 17, and 19 overpasses were all built in the 1958-59 period per uglybridges.com.   

My question: Was it typical to build bridges so low on those first generation interstates post Ike's interstate highway act?  (Too bad uglybridges doesn't give the bridges' clearances over what they're crossing.)

*GSV in August 2013 also showed the bridge at exit 13 (PA 501) as being under reconstruction, perhaps adding an inch or 2 to the clearance.

ixnay

The large trucks of the 1950s and 1960s were considerably smaller than those allowed later on.

[kkt]

The large trucks of the 1950s and 1960s were considerably smaller than those allowed later on.

So the better question is, "Why did they start building trucks taller than bridge clearances on major highways?"

[Beltway]

The large trucks of the 1950s and 1960s were considerably smaller than those allowed later on.

So the better question is, "Why did they start building trucks taller than bridge clearances on major highways?"

Clearances varied from state to state.  Some states could handle the taller trucks, so there were regions where these trucks could operate.  Other regions where they could not.