Georgia: three types of structure, three types of guardrail. Nine possible combinations of which seven were built and six survive.
This haunched T beam design with picket-style open concrete guardrail was common on the first sections of I-75, and there are still a few left between Tifton and Cordele. This one's on GA 316, though. Wait: here's one
in south Georgia, one of quite a few that were raised massively. The picket-style guardrail also was used on a few plate girder bridges such as
this one on I-75 near Ashburn, but never with precast beams.
This precast beam bridge with two-tube metal guardrail is also on I-75 in south Georgia. There's a surviving example of
the plate girder version on I-20 near Conyers. Further west along I-20 are two surviving examples of
the precast beam design, but with three-tube metal guardrail (if you look closely at the left end, you may be able to see that the guardrail on the end span is of a different type. I guess that the guardrail was damaged and they'd run out of replacement hardware!). There were plate girder bridges with the three-tube guardrail, too, but none of them survive.
And, out on what's now called GA 14 conn is a real unicorn:
a haunched T beam bridge with three-tube guardrail. I think that this is the only one ever built, and AFAIK there was never a T beam bridge with two-tube guardrail.
Oh, I almost forgot: At the tail end of the early Interstate era came this one example of a plate girder bridge with
early '50's-style bannister guardrail, on the I-85 Airport Connector in Atlanta. I have no idea why they chose this type of guardrail for exactly one location, but there it is.
In case anyone busts me... all three of these guardrail types were superseded in the early to mid '60's. First,
a bulky new type of open concrete guardrail came into extremely wide use between 1961 and 1964 or so, then abruptly fell out of use, presumably because it incorporated a dangerous so-called safety walk. There was also
a two-tube-metal design with a short concrete parapet used during the same period, almost exclusively in urban areas. There was also
a three-tube metal rail that was used for municipal projects but only rarely by the state. the GA 166 project in Atlanta used
single-tube rails that were apparently imported from Kentucky.
Starting in 1965, another type of really cool-looking metal guardrail appeared, in
one,
two and
three-tube variants. Shortly after came a new concrete design which a bud of mine dubbed
Florida Open Fence. These types prevailed until the introduction of the Jersey barrier in the late '70's. By this time, steel plate girder spans were ubiquitous- - no more concrete, precast or cast-in-place.
