Remember when some highway shoulders were topped with a thin layer of gravel?
It seems like there used to be a lot more roads where the shoulders were paved, same as the travel lanes, but were coated with a layer of ground rock. I think this was done (at least the only time I saw such a road being built) by spreading a layer of hot tar on the paved shoulder, then spreading (spraying?) the gravel on top before the tar cooled.
The purpose of this was presumably to make a noise when motorists drove over it so people wouldn't drive too fast or alert them if they dozed off. Today that same effect is achieved with a rumble strip on the shoulder; PennDOT at least called these "SNAP" rumble strips, for "Sonic Nap Alert Pattern". These are likely cheaper and can't "run out" of gravel eventually. Otherwise, most highway shoulders in my experience seem have the same pavement as the travel lanes.
IIRC some portions of I-16 (the oldest ones) have some gravel paved shoulders (narrow ones too). There's a lot of old, old sections on I-16, probably dating decades back.
What you're describing is basically bituminous pavement. Some areas (especially in the Midwest) still use such pavement for lesser-traveled roads. I believe changes in FHWA policy over the years have dictated that Interstate highways require a higher type of shoulder pavement, but not necessarily to the depth of the main travel lanes.
I've often seen concrete travel lanes with asphalt shoulders...MnDOT often does this outside the Twin Cities metro.
Quote from: froggie on November 10, 2014, 07:53:36 AM
I've often seen concrete travel lanes with asphalt shoulders...MnDOT often does this outside the Twin Cities metro.
That's been the NYSDOT and NYSTA standard since at least the 80s. Concrete expressways will have asphalt shoulders and exit ramps (in most cases). Shoulder gets less wear and plow action, so there's no need for the heavy-duty concrete. Exception is Region 6, which does use concrete shoulders. Contrast that with Ohio, which has been known to use
asphalt travel lanes and
concrete shoulders and exit ramps (especially around Columbus) for a reason I have yet to determine.
Quote from: cl94 on November 10, 2014, 02:21:03 PMContrast that with Ohio, which has been known to use asphalt travel lanes and concrete shoulders and exit ramps (especially around Columbus) for a reason I have yet to determine.
Are you sure that isn't an asphalt overlay applied to the traveled way only (possibly after grinding the concrete surface)?
In Kansas the norm is a full structural section for both traveled way and shoulder.
I suspect the use of chipseal on shoulders for warning drivers of errant vehicles has lapsed in favor of rumble strips, which are better for the purpose since the noise they generate cannot be confused with a simple change from one pavement section to another.
Another practice that was quite prevalent up to the mid-1980's, but has thankfully lapsed, is to use gravel or crushed rock for the entirety of the shoulder except for a narrow strip whose primary purpose is to help preserve the pavement edge and which was all but useless for helping errant vehicles to recover. Modern shoulders are now paved wide enough to accommodate a full-size car, and an increasing number of state DOTs now specify the so-called "safety edge" (beveling the edge of the pavement so that a car that gets onto the grass sideslope can turn back onto the road without getting one of its tires hung up, which can result in loss of control and lead to a cross-median accident).
Quote from: J N Winkler on November 10, 2014, 02:41:25 PM
Quote from: cl94 on November 10, 2014, 02:21:03 PMContrast that with Ohio, which has been known to use asphalt travel lanes and concrete shoulders and exit ramps (especially around Columbus) for a reason I have yet to determine.
Are you sure that isn't an asphalt overlay applied to the traveled way only (possibly after grinding the concrete surface)?
It is likely an asphalt top coat, but it's been in place since the road was built/reconstructed. Shoulder is at the same grade as the asphalt.
Quote from: froggie on November 10, 2014, 07:53:36 AM
I've often seen concrete travel lanes with asphalt shoulders...MnDOT often does this outside the Twin Cities metro.
Mississippi has done that with its new freeway sections (e.g. US 82 outside Starkville) and some widened freeway sections (I-55 in Southhaven, MS).
Seems like gravel shoulders started really going away in Alabama by the mid-2000's.