I realise this is a very broad-reaching question, so I’ll restrict it to the UK and the USA. Approximately how long ago could a journey between two sizeable cities be reasonably expected to be completed on “modern-day” paved roads? As concrete examples, let’s say London to Edinburgh, or New York to Chicago.
In the early days of the motor car? Further back in the horse-drawn carriage era? Or not until the UK Trunk Roads Act and the development of US interstates?
I’m finding it really hard to track down much info on when a network of paved roads was established.
Well, in the USA, the answer is definitely later than 1919. Check out the video of the first transcontinental motor convoy (in that year) at the bottom of the page.
The development of the American road system is extensively covered in Earl Swift’s The Big Roads: The Untold Story of the Engineers, Visionaries, and Trailblazers Who Created the American Superhighways. He covers the Lincoln Highway and also the dozens of others roads that competed with it and supplemented it. Highways were built point-to-point in America and to a multitude of standards. What constitutes “modern” is a matter of definition, but those named highways are probably the first to qualify. Roman roads may have been outstanding for their times, but they cannot be considered “modern.”
Well the OP did mention “further back in the horse-drawn carriage era” roadways; I do believe that the Romans used horses. That and I would consider the use of concrete as “modern”; this cross section of a Roman road looks better engineered than some that we have in Detroit today.
I’m going to say c1930 as far as “paved” roads. As a data point my 1933 map of Illinois shows that by then you could travel virtually anywhere in the state on a paved road.
As has been mentioned, a typical “modern” road with 12 foot travel lanes and 6 foot outside shoulders came later. The original Minnesota Department of Highways paving of the late 1920s was only 18 feet wide for the entire road.
Just like modern maps. “Paved” roads are shown as solid lines, and nonpaved roads are not. Usually modern maps just have paved and unpaved, but earlier maps broke it down further into “improved”, “graded and drained earth”, and “dirt”.
I have a recent South Dakota map that indicates which roads were paved with either a solid red line, a solid black line or a solid gray line depending on the type of road.
You do realize that they tar roads with asphalt because they can’t afford enough concrete don’t you? I learned long ago from my civil engineering professors that concrete roadways are vastly superior to asphalt covered roadways. They cited one of the reasons we see the orange barrels roll out every years is because the politicians are too cheap to purchase a road that would last; much better to have the slush fund reloaded every year.
The Romans invented concrete and used them in roads there roads but if you want to narrow your definition down that’s OK; it’s your question.
What came first: mass produced vehicles capable of maintaining 55mph or paved interstates?
If paved interstates came first what was the typical beginning cruising speeds on them?
Road quality varies drastically from state to state. Back in my childhood (early 70’s) we envied Texas and Tenn for all the multi-lane roads they enjoyed. My state, Ark was mostly 2 lane highways. Louisiana had just horrible roads. Our fishing cabin was in Claiborne Parish, Louisiana and we drove into Louisiana regularly.
We had a lot of County gravel roads in the 70’s. Driving one of those was always an experience. Any speed at all and you’d find yourself sliding around. State highways were 2 lane blacktop. Often very, very narrow. Bridges were scary if two large cars approached each other on a bridge.
On trips crossing into another state, the road quality was very noticeable. Unless you stayed on the Federal Interstates.
My speedometer goes up to 160 mph. I’ve never come anywhere close to it. And there is no road in America that has ever allowed it legally. Cars could go faster than the road speed limit from near to their beginning.
You need to come up with a cite for your assertion regarding the superiority of concrete roadways from a less biased source than a trade association (the Concrete Paving Association of MN) dedicated to supporting concrete paving.
Also, note that concrete roadways are not just a little more expensive, but vastly more expensive to install than asphalt roadways. They are also much more expensive to repair, and concrete roadways have a tendency to crack, especially in snowy areas that experience freeze-thaw cycles and are snowplowed.
Asphalt roadways, on the other hand, are easily milled up (and the millings are recyclable), and new asphalt can be easily and rapidly laid down. If the road cross-section is sound, then often just the top layer (often referred to as the wearing course, and usually about 2 inches thick) can be easily milled off, and a fresh wearing course installed.
As for longevity of concrete roadways, if the roadways have underground utilities installed in the road, you have to take into account the expense of sawcutting, jack-hammering, excavating, and restoring the roadway every time you conduct a utility repair or replacement, regardless of the lifespan of the roadway itself.
I’m not trying to be an apologist for asphalt paving–I’m just saying that it’s not as simplistic as saying that “concrete roadways are vastly superior to asphalt covered roadways.” As for asserting that the only reason that asphalt is used is because “they can’t afford enough concrete,” well of course relative costs come into the equation. You might just as well say that that’s why we don’t pave the streets with gold.
Tarmac roads go back to 1834, even though they were not common until later. They ought to count as paved. Macadamised roads without the tar go back further, to the 1820, and were reasonably common in 19 century Britain, I think. I am not sure if they will count as paved for the OP. (But if they do, why not the Roman roads, or the streets apparently tarred in the 8th century AD?)
Incidentally, I do not think it is very colloquial British English to speak of a modern road surface as paved (although professionals may do so). In Britain, paving usually means a surface of large stone or concrete slabs. In this sense, Roman roads were paved, but modern roads are not. Also in Britain, the pavement (which often does consist of such slabs) is what Americans call the sidewalk, and the road surface where you drive is certainly not pavement.
That and I would consider the use of concrete as “modern”; 
