Differences in how US routes are handled between western and eastern US

[ClassicHasClass]

That is probably what the numbering system should have been from the get-go.  I really like how Mexico did this concept with the Federal Highways and Autopistas.  The brand recognition thing with the Interstates could have been simply a red/white/blue US Route shield along segments that met certain design standards.  Certainly, it would have spared the road community (not that I'm suggesting this is important to the normal traveler) much of the Interstate grid perfectionism which plagues the hobby.

I think this could have worked. I think Australia does something kind of similar, too.

If you mean the M-A-B-C grading, yes, although this is not consistent since not all the states are on that system.

If you mean the old NH-NR distinction, that was closer to US route vs Interstate, even though most NH alignments were not freeways and most NRs were sealed through routes (compare with Tracks). SRs were always sui generis as they are here.

[JREwing78]

Folks have touched on this item, but I think it bears further explanation.

East of the Mississippi pre-1950, the US had much more of the population than west of the Mississippi, and there was a greater demand earlier for road building. Many of the important US highways were built out before the development of high-speed roadway design standards, including access management. These routes would not be suitable for later in-place upgrades to Interstate-standard freeway.

Road funding was also less free-flowing, partially due to the Great Depression and WWII, so what improvements were made were done with a short-term mindset rather than with considerations 50 or 100 years down the road. Therefore, there generally was no simple widening of important US routes; typically they were supplanted by tollways like the Pennsylvania Turnpike, Indiana Toll Road, or New Jersey Turnpike, or later by a federally-funded Interstate highway.

Out west, those tollway/Interstate highway improvements came later on, and more sparsely, than out east. However, they also were later to the game with highway improvements in general. At that point, those US routes not supplanted by Interstates were being built out to more modern standards, including more gradual curves (both horizontal and vertical), wider Right-of-Way, and more room for later widening as needed. The fact that there were fewer homes/farms/businesses encroaching on the ROW needed to begin with facilitated use of these modern standards, and there were fewer NIMBYs to have to appease to get a road built. These differences allowed higher speed limits to allow people to safely reach their more far-flung destinations faster, in many cases on par with a comparable Interstate highway.