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[Tom958]

Wyoming is truly fascinating, for those who are into such things. Most other states have a standard or near-standard Interstate median width of sixtyish feet. Not Wyoming, though. Most Wyoming Interstates have medians of either 36-44 feet or... 125 feet! The upshot of this is that the overwhelming majority of grade separations on Interstates have the freeway passing over the lesser road, presumably because of the expense of bridging over such a wide median. Or maybe I have it backward: maybe the ultra-wide typical medians are the might-as-well product of the decision to take the freeway over the lesser road. Anyway, another upshot is that the number of bridges in the class that this thread is about is rather small, apparently small enough that they were designed on a small-batch basis rather than being churned out by the score to a few typical designs as in most other states.

The freeway-carrying bridges are almost invariably simple concrete slab structures of which this structure on I-25 near Slater, built in 1958, is an early example. The rather dainty-looking metal guardrail neatly integrated with the ground-mounted box beam guiderails is ubiquitous in Wyoming. I wouldn't have expected such similarity between New York and Wyoming, but here we are. Actually, I think that Wyoming is even more committed to this type of thing than New York is, probably to minimalize snow accumulation. These bridges have full-width shoulders, too, despite their early construction date and their remote location. That's gotta help with snow, too.

That particular structure has round concrete columns, a bent cap, and a slightly-thicker slab near the bents. However, there are several variations throughout the state. This one on I-90 at exit 178, from 1960-63 best I can tell, uses round steel piles instead of concrete columns. I think that this one at on I-90 near Carpenter is my favorite, with concrete columns, a flat slab, no bent cap, and no edge treatment, not even a reveal. It's from 1965. This one on I-80 at exit 238, built around 1969, has steel H piles and shallow tee beams instead of a flat slab. I'm wondering now if the tee beams were an evolutionary development, replacing the flat slabs. I'm too lazy to track it down, and it'd be off topic for this thread, anyway. Since I mentioned it, though, I'll give a shoutout to this guy on I-25 at Chugwater, from 1968. It's a full monte tee beam structure, built at a time when other agencies had generally gone to plate girders, precast beams, or box beams (Wyoming uses plate girders, too, but they're not as interesting).

Back on topic: This prosaic plate girder structure on I-25 near Slater, built in 1958, is  the kind of thing I would've expected to find throughout Wyoming's early Interstates. Note the steel channel guardrail. Just to the north is this one with a two-tier steel channel guardrail  that I haven't seen anywhere else, in Wyoming or elsewhere. I'd like a closer look, but the Streetview quality on top is poor. On both of these, the haunches look tacked on, as though they were an afterthought, and there are haunches at the abutments, which is rare. Hmm...

Now, the good stuff. Yes, Wyoming built its share of handsome tee beam bridges in the pre- and early Interstate era, and many of them are still around. This one carrying Country Club Drive over I-25 in Cheyenne was built in 1957. Note the unusual four-tier metal guardrail. A few miles south is this one carrying I-25 over Missile Drive, also from 1957. I wonder if the light metal guardrail is original equipment. There also this one-off very skewed tee beam structure for northbound I-25 over southbound US 85 where the two part ways for good. And, this near-repeat of the Country Club Drive bridge, built five years later in 1962, at the east end if Laramie's I-80 bypass. It uses an unusual pedestrian-friendly three-tier guardrail even though the interchange it's in is a trumpet designed for free-flowing traffic, and there's no sidewalk. One of those little mysteries.

Finally, while it's neither original Interstate nor standard, I feel like I have to mention this Missouri-esque ultra-economical flat slab structure on I-25 near Wheatland, built in 1966. With its W beam guardrails tacked onto the sides ala Texas at its chintziest, this is the type of thing that I feared would dominate the state. Happily, though, this is the only example I found, which makes it an adorable unicorn.

And, speaking of off-topic unicorns, I must also mention the three-level stack interchange at I-25 and US 26 north of Wheatland, also from 1966. When I posted about it on Facebook (the Road Enthusiasts group, if you're interested), there was some consternation over the use of a design with left-hand entrances and exits, but its merit as an exercise in structural engineering and highway agency policymaking is undeniable. There's another three-level stack at I-25 and I-90, but it's more conventional (i.e, heftier) in design. Despite its being built in 1964, it looks rather futuristic to me, probably because it resembles typical California box beams, but they didn't start using light metal guardrails like Wyoming's until the seventies, AFAIK.

[thefraze_1020]

That was fascinating! Thanks for that!

[Tom958]

That was fascinating! Thanks for that!

My pleasure. I hope you enjoyed it as much as I enjoyed your post about Washington! 

[thefraze_1020]

That was fascinating! Thanks for that!

My pleasure. I hope you enjoyed it as much as I enjoyed your post about Washington! 

Touche!

[Tom958]

Montana: more tales of the unexpected, at least for me. Like Wyoming, it seems to have a pretty high proportion of 36-44 foot medians, though there are a few of great width as well as numerous mountain stretches with minimal, Jersey barrier medians. Also like Wyoming, the Interstates pass over lesser roadways rather than under to an unusual degree, at least on the older Interstates.

I'm gonna start before the beginning with this handsome tee beam bridge on I-90 over the Little Bighorn River just south of US 212, built in 1956 for US 87 and now the eastbound roadway of I-90. The metal banister guardrail is typical for the era, believe it or not. It's been augmented in this case by bolted-on W beam guardrail, though, as you'll see, thrie beams and cast-in-place parapets are used elsewhere. There's also this tee beam bridge on I-115 in Butte, built in 1957, with the same guardrail. Surprisingly, though, that's about it for tee beem freeway bridges in Montana because...

At the beginning of the Interstate era, precast concrete beams a la today's AASHTO beams pretty much took over in Montana. They're every bit as prevalent in Montana as they are in Florida! This bridge carrying I-15-90 over Harrison Avenue in Butte, built in 1960, is a good example. Note the distinctively-shaped bents as well as the insane guardrail. A bit further to the west is I-19-90 over S. Montana Street, built in 1961, modified in 2004. Note that the main spans are plate girders, but the side spans are precast. The westbound bridge retains the original guardrail augmented with W beams, but the eastbound has concrete parapets instead, with two different edge conditions.  I dunno, either. The parapets are vertical and flush with the former "safety walk", not Jersey barriers. Jersey barriers as bridge parapets are rare in Montana.

Out in the country, here's a randomly-chosen bridge carrying I-90 over Jens Road, built in 1959. The parapets have been replaced more neatly than the ones in the previous entry. Then there's I-90 over Dunmore Road, also from 1959, with thrie beams and... not the same slab edge condition. Wassup with that?

The interesting thing about those last two and many others like them is what you don't see: for whatever reason, the ultra-economical flat slab bridges found throughout the west are very scarce in Montana. The only ones I found were two sets on I-15 in Teton County, and they weren't built until 1972! Wait: here's another set on I-15 near Great Falls. It was built in 1969. So, still.

Sometime in the early sixties, the metal banister-style guardrail was superseded by a downright bizarre contraption of W beams and pipe rails, the most oh-hell-no guardrail system I've ever seen. In a double whammy, I'll present it to you c/o this epic straddle beam bridge carrying eastbound I-115 over westbound I-15-90. Unsurprisingly for Montana, while the central spans and straddle bents are steel, the end spans are precast. Needless to say, that crazy guardrail design is used on more prosaic bridges throughout the state. This one in particular, built in 1967, caught my eye. For no obvious reason, it has one plate girder span while the rest are precast. WTF?

Also very much worthy of note is this strikingly un-Montanan pair of tee beam bridges on I-15 at Ulm, built in 1962, and reminiscent of these bad boys in Mississippi, of all places. Unfortunately, while Mississippi provided an attractive open concrete guardrail, Montana went with a veritable dog's breakfast. Note the double wooden blocking behind the W beam, which is deteriorating visibly. I surmise that they did it to bring the face of the W beam out to the face of the "safety walk" to combat the dread bounce effect.  Wait, though: the dog's breakfast guardrail is only on the northbound side. The southbound sports the tube steel-and-short-parapet design that became dominant I guess in the seventies. That's because I-15 here was originally built as a super two. The second roadway wasn't built until 1969, making it all the more remarkable that the bridge was built to such an unusual design. I checked bridgereports.com across the entire state for an over-the-freeway bridge of this design, but I didn't find one.

I'll close this out with a unicorn, on I-90 over the Little Bighorn River.  This 1948 structure with a two-tiered open concrete guardrail was built in 1949 for US 87 and now carries eastbound I-90. The northbound structure was built in 1959 and retains the metal banister guardrail on the outside.

Off topic, but since we've come this far, here's a typical bridge from the later Interstate era, built in 1970 when that second roadway of I-15 was added. Precast beams, plenty of right side clearance, round columns with pill-shaped bent caps, and the tube steel-and-low parapet guardrail we saw earlier.

 

[on_wisconsin]

Wisconsin Interstate bridges (late 50's - early 80's)

Typical steel superstructure designs:
Curved beam (Probably the most common from the era.)
https://goo.gl/maps/fu3ePjTtW7XV1EN3A
https://goo.gl/maps/74HzxRcdFdKrLEUn9
https://goo.gl/maps/ycrXJV1vUtcfvHxM6
https://goo.gl/maps/wKShfD1hrDbmRF3TA

Straight beam
https://goo.gl/maps/H85sWWsjeLUoS8xLA
https://goo.gl/maps/3vws7TQJKBp85Njc8

Concrete:
Cast-in-place
https://goo.gl/maps/nZZgQR2WCEtH8LFcA
https://goo.gl/maps/NDhLr4BLyTMfiQoR9

Beam
https://goo.gl/maps/tgyaAXKxkqb4Ss9F9
https://goo.gl/maps/FQjL7stmJtLTzvxx9
https://goo.gl/maps/5FWpMmDGVf12HKGG7
https://goo.gl/maps/onkoSvkCniLrRkTD7

[Tom958]

Iowa. The first several are from Cass County in western Iowa, where most of I-80 was completed in 1958-59. I'm not at all familiar with the state and it's not interesting enough to research extensively, but I'm gonna assume that these are fairly representative. Corrections are welcome, of course.

670th Street over I-80. Off to a strong start aesthetically with precast beams on distinctively-shaped T columns. This one lacks the prominent diaphragm at the bents seen on many of its counterparts. The guardrail looks like a Jersey barrier, but it's not, as you'll see. OT, but that bullnosed W beam guardrail in the median seems like a bad idea.

IA 148 over I-80. Same basic design, though the diaphragms are more visible and the bridge has been raised a couple of feet or more.  Here, the original rather unconvincing two-tube metal guardrail was left in place, with a vertical concrete parapet added on the traffic side. Here's what it looks like from above.
 
Between those two is I-80 over 690th Street. The bents are similar aesthetically to the T columns we've just seen, but they're slightly flared at the bottom, like the pants that'd become popular ten years later.  That little flare must've been a pain to form, so points to Iowa for both effort and aesthetic results on this one.

Sadly, though, the gluteal distress got to be intolerable, resulting in this much more prosaic bent design with round columns and a pill-shaped cap. I find it unpleasantly surprising that the guardrails haven't been replaced, especially since the deck width is only 29.9 feet per http://bridgereports.com/1107387. At this point, they must be holding out for full replacement. At 10,000ish, the ADT isn't that high, but trucks are 39%.

Here's its over-the-freeway counterpart at 620th Street over I-80. This bent cap is squared off and slightly beveled upwards at the ends rather than being pill-shaped, though both variants are in evidence nearby. Speaking of which, here's York Avenue of I-80, in Adair County just to the east. As you can see, it has the pill-shaped bent caps, three columns instead of two and the original guardrail with no concrete parapet. It was built in 1959 and modified (raised, I suppose) in 1972. I wondered if the T bents were used where the deck was narrower, but this one and the T column bridges are both 24 feet between curbs.

Further east in Dallas County, and a bit more interesting, is E Avenue over I-80, built in 1960. It's a reprise of the T bent design, but with steel plate girders instead of precast beams. I-80 has a median of 50 or maybe 52 feet through here. Where it runs due east-west and intersects the lesser roadways at ninety degrees, precast is used, but where there's a significant skew, they go to steel. Further east still is 347th Street over I-80, with the original guardrail still in use, and painted green. it was built in 1966, so I guess the original designs persisted for quite some time. There are several other plate girder bridges between here and E Avenue, but this one with the original guardrail reminds me of my own state of Georgia. Georgia's metal guardrails are better looking, though.

The reason I surfed so far east was that I was trying to find a better shot of something like this concrete slab bridge in I-80 over 570th Street back in Cass County. Unlike in more western states, these must be pretty scarce, and this one was built in 1966. Perhaps there are other early examples that I haven't found, or perhaps Iowa really didn't start building these until later on, as was apparently the case with Montana. There are other similarities between Iowa and Montana, too. Hmm...

Finally, and arguably off topic, here's the three-level interchange of I-80 and I-880/former I-680, built in 1966. I was very surprised to find a concrete slab bridge at the middle of a three-level interchange between two Interstate highways, but here we are (I'll give a shoutout to the even more spectacular interchange of I-25 and US 26 in Wyoming, built at about the same time). Traffic volumes must be quite low, and the deck is only 23 feet curb to curb. Also, the clearance to the top-level bridge is only 14.4 feet. Not good. The steel plate girder bridge for westbound I-80 was modified in 1989, presumably to add the shoulders and install Jersey barrier parapets on both sides.

[roadwaywiz95]

For this upcoming weekend's Webinar presentation, we'll be taking a look at the bridges that span the Hudson River, with the primary focus being on the Capital District and Hudson Valley regions of New York State. There are many interesting & historic structures to discuss and we will be dissecting their history and importance as only the folks of the AARoads Forum can! Coverage will begin on Sunday (12/20) at 6 PM ET and will feature live contributions from members of this forum; we hope to see you there!

[cjk374]

Louisiana:

1959: the 3 oldest bridges over I-20 are all in Ruston. https://maps.app.goo.gl/iFGxcYfFUM4oe9Ka6


Early 60s model:  https://maps.app.goo.gl/8qpGr82ZQREtoAHK9

Then Louisiana ran out of money trying to build I-20. It would be almost 10 years before they started building I-20 between US 79/80 (near I-20 MP 41) to the Industrial Dr. exit in Bossier City (MP 23). You can definitely tell a difference of the decades with the bridge designs (and other things as well).

Early/mid 70s style: https://maps.app.goo.gl/ZAEqKZhjjK8HHYjg9


And of course, 80s thru modern day:  https://maps.app.goo.gl/uNxXyYpDsEXCqhYv7

[Tom958]

Kansas is somewhat similar to a few other states in that it settled on a few standard designs early on and stuck with them for what I'd say is an oppressively long time. That said,
the designs themselves are both more attractive and more interesting than those in, say, Kentucky or Alabama.

KS 23 over I-70, 1960. An elegant cast-in-place concrete box beam with single round columns, an arch-portaled open concrete guardrail and Deco-looking curved endblocks. This one's in my personal pantheon of early Interstate bridges. Withough looking too hard, I found plenty of bridges of the same design built in 1965, too.  The design is used indiscriminately regardless of intersection angle and resultant span length. It anything, the design is too ubiquitous, though the newer section includes a couple of these, which appear to be identical except for having the same Kansas Corral guardrail as the freeway-carrying bridges of the era. That one was built in 1964. From slightly earlier, in 1958, there are some of these guys, which appear to be identical except for having very slim twin round columns instead of the larger single ones. I found a twin column, Kansas Corral variant from 1964, too.

While they're rare, steel bridges do exist in Kansas. Here's one, with rather handsome lightly-haunched plate girders and Kansas Corral guardrails. It's from 1962. Or so they say. Those bents look modern to me.  And not far away is its AASHTO beam cousin, from 2002.  It's rather surprising that the end bents aren't any further from the roadway than they are.

Also from 1958 are numerous examples of these startlingly spare concrete slab structures with the hefty but short Kansas Corral open concrete guardrail. All the Streetviews of the 1958 structures are crappy, so I used a seemingly-identcal one from 1965 instead.

There are numerous culverts for very-minor roads. This is a scarce Streetview of one that I stumbled upon.

Though they're actually pre- rather than early Interstate, I must give a shoutout to the bridges of the Kansas Turnpike, all from 1956. They're mostly plate girder versions of the box beams we're now familiar with. The capless bents are a distinctive feature, and they use that same iconic arch portal guardrail. Also, here's the Matfield cattle crossing, http://bridgereports.com/1716873. Wait: Here's another design, providing some welcome variety: sheer taper bents and a two-tube metal guardrail. And, there are a couple of other bent designs for the standard bridge, including this sheer taper version. Finally for this report, there's this heavily-skewed bridge, obviously rebuilt recently despite what http://bridgereports.com/1206187 has to say about it. Many of the original bridges on the I-70 part of the Turnpike have been replaced, but fewer on the other sections.

Interestingly, the turnpike-carrying bridges are invariably hefty plate girder structures, not the ultralight concrete slabs found throughout the early Interstates. KDOT obviously went through a major rethink on this. 

Off topic, but... as ubiquitous as those early box beam designs were, I found myself wondering what KDOT built in later years. Here's a California-looking box beam with a single tube and low concrete guardrail on I-35, built in 1973. Where the skew angle is more severe, they went to this design with arched plate girders. Oddly, the bridges over watercourses on this segment of I-35 are tee beams, which require falsework (http://bridgereports.com/1202437). I'd expect to find this design used over roadways instead of the ubiquitous concrete slab design where the skew angle is severe, but I haven't found any such structure.

[Tom958]

Illinois is more diverse and interesting than I'd realized. For those who don't know, the subject of early Interstate bridges interests me enough that I've done a series of Streetview-illustrated posts at the Road Enthusiasts Facebook group. For Illinois, I examined all the rural Interstate segments that were open per the 1962 official state map and posted about three of them, the others being either redundant or the bridges being too prosaic in appearance. Both here and on Facebook, I've thus skewed my presentation toward making the subject look more interesting than it actually is. Sorry.

Perks Road over I-57, built in 1962, is an example of what may be the most common type of early Interstate bridge in the state: a simple plate girder structure with fat T bents. It retains the original metal guardrail in addition to a second set of metal guardrail added later to augment the first and perhaps to eliminate the bounce effect of the original "safety walk." I consider the appearance to be pleasantly intricate, though some might consider it cluttered. While green is the usual color for these guys, they come in blue, gray, and a good many recently painted brown.

There's a less-common tee beam counterpart to that design, exemplified by Westminster Road over I-57, built in 1959. I was expecting to find a precast concrete version, too, similar to what Iowa built early on, but I never did. No, wait: Here's one. It's Beal Road over I-57, built in 1967. It features a handsome rounded parapet soffit, used on a variety of designs across the state, plus the single tube-concrete parapet guardrail that more or less took over the nation's highway bridges until the Jersey barrier took over. Even as subtle as the curve is,  it causes this design to remind me ever so slightly of the iconic curved-bottom bridges on I-280 between San Francisco and San Jose.

Before I get too far along, here's an end-on closeup of that style of guardrail. I don't know that I've ever seen a curved channel used in a guardrail before, though from a normal viewing angle it looks like a tube, so I may have seen it elsewhere and not realized it. This photo also shows bolted-on thrie beams rather than the steel tube guardrail I mentioned above augmenting the original rails.



The photo comes from the Bridgehunter entry about the Fairmount Lane bridge over I-55-70, one of the unicorniest structures on the entire Interstate system. Long may it stand. That said, it started its existence as a variation on the fat T tee beam I mentioned above, with a two-column bent to accommodate the skew angle it's on.  Actually, that two-column bent is fairly common, too, as on  I-70 near Effingham, which was open in 1962

Changing gears completely, there are quite a few very prosaic precast beam bridges with round columns and rounded-end bent caps like you'd see in South Carolina rather than the iconic tapered columns that dominate Illinois. Here's one on 100 East Road over I-74, built in 1959, but there are quite a few on I-80 as well. This bent design is also used for plate girder bridges, which I find too unremarkable to list here but which seen to dominate several Interstate corridors.

Further east on I-74 are a couple of tee beam designs from 1962: one, and another. Normally I'd appreciate the variety, but in this case, the bridges across the line in Indiana are also tee beams and are very similar in appearance. 

Speaking of tee beams and variety, there are a couple of apparent one-off designs I've seen which add some variety, I'd like to think just for the joy of it. For example, this handsome tee beam structure carrying Grassy Road over I-57, built in 1959 and unfortunately in bad shape. Not far away is friendship School Road over I-57, also built in 1959, a plate girder bridge which crosses I-57 and its 110-foot median (!!!) with only three spans. Off topic, but I wish to mention that the early section of I-57 between Dongola and Marion is a surprisingly luxurious highway, with a variety of median widths and treatments in addition to the variety in bridge types. I think it'd be a welcome respite after 150 miles of brutal boredom on the way from Memphis to Chicago.

One more: In Champaign are several of these: plate girder bridges with prosaic superstructures, but with bents that are so whimsical in shape that they're almost Googie. They were built in 1956, which means that they were under construction before Ike signed the Interstate act.

[Tom958]

Idaho: In doing these things, I've learned to expect the unexpected, but Idaho is the first state where I took at least a cursory Google satellite look at the entire Interstate system. Why? Because I found something really interesting early on.

As you likely know by now, the earliest Interstate standards called for a forty-foot median, and accordingly many states started out with medians of about that width. Later on, sixty feet came into favor, and both sixty and 64 feet became prevalent in most states throughout the period of the most rapid expansion of the system in the 1960s. Idaho, however, decided on 75 feet as its standard, and the overwhelming majority of its Interstate medians are 75 feet or thereabouts, the major exception being, obviously, in mountainous areas, including most of I-90 (I've often wondered why the Feds signed off on different median width policies in different states, but that's a question for another day).

Something else I've noticed in my research: As you know, early Interstate bridges tended to be either steel plate girders, cast-in-place concrete tee beams, or the then-relatively new technology of precast, prestressed concrete beams. However, there seems to be a period during which the span lengths required to accommodate a sixty-foot median were in excess of what was considered viable for precast beams. Therefore, several states either stopped using them in favor of plate girders or settled for narrower medians, e.g. fifty feet in Iowa. Idaho, though, took a different approach, as you're about to see.

Black Canyon Road over I-84, 1960. This happens to be the first entry for I-84 in the westernmost Idaho county through which it passes, and it's as good a place to start as any. As you can see, Idaho was so committed to its 75-foot medians and to precast prestressed concrete beams that they accommodated both by adding an extra span over the median. Of course, extra spans over wide medians are hardly unheard of in other states, but Idaho did this pretty much everywhere for a long time.

This bridge features a bolted-on thrie beam replacing the original guardrail. Its round columns and pill-shaped bent caps render it pretty much devoid of aesthetic interest. Unfortunately, this type and the variant in the next entry dominate Idaho's Interstates.

Not far to the east is Sand Hollow Road over I-84, 1962, with a handsome but anachronistic banister-style metal guardrail. This wider view also shows the lengthy stretches of guardrail needed to protect the median bents, as close as they are to the traffic lanes. Barely visible at the end in this 2019 view, the endblocks are being recast. Wassup with that? The Streetview shows 1962 cast into them. I wonder what date, if any, is cast into them now.

Continuing eastward at a bit of sacrifice to the narrative, here's ID 44 over I-84, 1964. This one has plate girders with stiffener plates instead of the usual precast beams, and the banister guardrail is augmented by thrie beams. Oddly, despite choosing to go with steel here, they stuck with the extra span in the median, contrary to the practices of most other states.

We've now seen the most prevalent two types of bridge guardrail in Idaho. And it's usually one or the other, not both together as seen here.

Alas, I'm not energetic enough to pin down the year when they gave up on the five-span thing, but  US 30 over I-86 near Pocatello, built in 1968, is probably a fair representation. I reiterate: these boring-ass bridges dominate the state to a truly astonishing degree.

Surprisingly considering Idaho's early fondness for precast beams, cast-in-place tee beams are the predominant type of early Interstate mainline bridge. This one's I-84 over Purple Sage Road, built in 1962. The thrie beam guardrail is also very common, with Jersey barriers being quite rare. There are also quite a few culverts for lesser roads, but the simple concrete slab bridges seen in other western states are apparently not a thing on Idaho Interstates. Later on, precast beams became prevalent for this class of bridge, usually with thrie beam guardrail.
 
Ditto Creek Road (or is it Cleft Road?) over I-84, 1959, modified in 1978. The original precast beams were replaced with shallower voided slabs. Now the vertical clearance is 16.4 feet. I saw a couple of these on I-15, too.

Here's a surprise: ID 37 over I-86, built in 1959, is all voided slabs! The guardrail is an actual Jersey barrier, too, which is rare in Idaho. It must've been added during its 1985 rehab.

Shifting eras, here's Rainbow Road over I-86, 1972. It's a perfectly legit cast-in-place box beam bridge, its rectangular rather than trapezoidal cross section placing it slightly on the conservative side of the awesomeness spectrum. What I find striking about this structure and its contemporaries is how Idaho went from five painfully short spans to two spectacularly long ones in one leap, with no intermediate, evolutionary phase. Not too far away is the Osborn Loop over I-86. Built in 1981, it's a bit disruptive to my narrative, but too handsome to ignore. Unusually, it has a two-tube metal guardrail that extends far past the end of the bridge a la Wyoming, something I haven't seen elsewhere in my virtual travels in Idaho. Also, the only other place I recall seeing that guardrail was on a bridge built in 1964!

While we're in that area: I mentioned earlier that there are numerous culverts for lesser roadways in Idaho. This shot, along the western portion of I-86, is kind of a twofer: it's also along one of quite a few sections where the median goes to 175 feet for a few miles before returning to the usual 75 feet.

Idaho did steel plate girders in the early seventies, too. Here's US 91 over I-15, 1971. Unlike the two box beams in the previous entry, this one has four spans instead of two, likely because it's on a 44 degree skew angle. It also sports thrie beam guardrail in what looks like an original installation instead of that single rail-low parapet rail we saw a couple of posts back. I'm really starting to wonder when the thrie beam was first introduced. Idaho must've been an early user.

Immediately to the south is Bowman Road over I-15, also built in 1971, with two spans and the expected guardrail for that era.

And, immediately to the south from there, is this thing of beauty: i-15 over ID 40, also built in 1971. The northbound and southbound structures have different guardrails and two bridgereports entries, but they were supposedly modified only a year apart, in 1987-88. There are several pairs of bridges like these in the area, but they all have Jersey barriers on both sides. I dunno, man.

Finally, almost to Utah is this handsome pair of cast-in-place box beams carrying I-15 over ID 38, built in 1975. This is at Malad, and there's another set at ID 36 on the other side of town, but the remaining bridges between there and the Utah line are precast, with normal-looking bents and this same guardrail. Perhaps they built these at Malad for aesthetic reasons.

[Tom958]

South Carolina is all too easy. It's dominated by a design with open concrete guardrails and bents with round columns and pill-shaped caps. There are precast, tee beam, and plate girder variants, though the precast one is by far the most common: I almost gave up on trying to find a plate girder example for this feature.

While it was augmented by other types, that open concrete guardrail design persisted into the seventies, as exemplified by SC 39 over I-20, built in 1970. As standards for median widths and side clearances increased, plate girders became dominant, but I did find this precast example carrying Ridge Road over I-20, built in 1968, where the spans are shorter than its steel counterparts due to lesser side clearances and almost no skew. Wait: here's a better example: SC S-28-47 over I-20, built in 1968, with minimal side clearances but a wider median at 70 feet versus 60.

Speaking of guardrails, I feel compelled to mention this hideous thing, which appeared for a few years in the mid sixties. It was also used on this rather spectacular set of structures near Charleston, which were recently replaced.

Not on an Interstate, but it would be remiss not to mention these bridges on the expressway section of US 29 northeast of Anderson, built in 1957 and presumably designed in the pre-Interstate era. The guardrail is about five inches deep (yes, I've inspected it up close), and the date is stamped into the curb. The section of I-85 from US 29 to I-185 was completely rebuilt in the early eighties. I suspect that it was similar in design to this section of US 29; the archaic interchange layouts are visible at historicaerials.com. One of these structures was badly damaged by a vehicle strike and is said to be up for replacement. Too bad, IMO. This stretch of highway should be a roadgeek icon.

[Mapmikey]

More on South Carolina...

The "hideous" rail was everywhere in the Charleston area and goes back to at least 1957 on the Sumter bypass (first freeway in SC).  Examples also existed in Columbia (I-20 @ US 176) and Greenville (this one dated 1958) for sure.

open concrete rails on interstates made it to at least 1973 (I-95 @ US 176) and I know they were using this as early as 1958 on other I-26 bridges.

This interstate overpass was probably contemplated before the offiial interstate system was set, but was a common bridge design throughout South Carolina on non-interstates.  This is I-585 at SC 9, built 1958.  At least one more is on I-185 in Greenville. This style was in use from about 1940 through the late 1950s.  I have seen one example where the rails were surrounded by a wood "box".

The jersey wall with single rail got in use as early as 1973 on I-77 in Rock Hill

South Carolina got creative with I-77 south of Rock Hill with what I thought as a kid was a futuristic looking bridge - from 1980

[Tom958]

More on South Carolina...

The "hideous" rail was everywhere in the Charleston area and goes back to at least 1957 on the Sumter bypass (first freeway in SC).  Examples also existed in Columbia (I-20 @ US 176) and Greenville (this one dated 1958) for sure.

There was also exactly one on I-85, near Anderson on a bridge that's since been replaced. As a kid, I thought it looked like something the Nazis would've come up with. I spotted and looked up the ones on the Interstates in Columbia and Charleston when I was working in Charleston in 2012-13, but I was unaware of their use earlier.

Open concrete rails on interstates made it to at least 1973 (I-95 @ US 176) and I know they were using this as early as 1958 on other I-26 bridges.

I took I-20 from Georgia to Columbia not too long ago, and I was struck by how anachronistic that rail design looked. That said, my own state of Georgia went through three successive open concrete guardrail designs, and SC's was better than at least the first two. No wonder they kept using it.

[andrepoiy]

In Ontario, the original bridges dating to the 50s are slowly being phased out.

Highway 400 at Kettleby Road
Old:

New one being built:


Highway 401 at Brock Street
Old:

New: