I have no figures and few facts but rail could be easier to maintain then roadways since the roadbed is hidden below pavement while the railtracke can be adjusted and the macadam worked with.

But on the other hand railway maintainace disrupts the traffic flow much more then road maintainance...

I think the biggest difference if you started from scratch would be larger loading gauges for wider and higher loads and higher unified platforms. This would at least be relevant for most european countries. The wheelbase dont matter as much.

If you had enough rail to have two complete systems it could make some sense to have a narrower wheel base for light and medium heavy rail passenger only traffic and a wider one for cargo and long distance travel. But this probably only made sense in earlier times when earth moving equipment were primitive and concrete expensive and the smaller turning radii of a narrow wheelbase mattered a lot for the building cost. Large parts  of southern Sweden once had a 891 mm network, three swedish feet from before metrification. One small part of the 891 mm network have survived for commuting to Stockhom and there are a few museum railways. The rest is either scrapped or widened to standard gauge. Had those lines been built now none would have been built as narrow gauge.

There are differences between now and then. The war time electrifications in the early 40:s disrupted the traffic flow a lot less and where made faster then those being made today in Sweden. Back then most of the labour were done manually, they used manny more workers, the equipment installed where lighter and security procedures much simpler. They could more or less suspend working within a few minutes and step off the track when a train approched.
But that were an mobilization effort and today we optimize for cost with a completely different cost for labour and other machines being available.

The big change over that jokuhl/Bob Fiske referred to occurred not in the 20th century but in the 19th. When railways were originally developed in Great Britain, the Great Western Railway used a track width of 7 feet. All the other companies used the standard width of four feet eight and a half inches.
The differences obviously led to problems and, with the aid of  a large number of navvies, the Great Western was converted to the standard gauge. If memory serves me right, it took a weekend for the conversion, but presumably the amount of track was small at that time.
astronomer1

The new Swiss rail tunnels, where speciality freight will move  at 160 kph/100 mph and pax as fast as 250 kph, are being built to a 100 year standard.  No major maintenance for a century despite over a dozen trains/hr (both ways).

Japan rail is all narrow guage 3.5 feet except their high speed rail network.

I would have built the track gauge slightly larger (New Orleans gauge of 5'2.5", 6 inches wider than standard) but with wider loading gauge and more overhead clearance.

Biggest change would be electrifying every rail line.  Perhaps  every other frieght car would have 1 electric motor and one driven axle.  This would increase traction, acceleration & braking and allow for steeper grades on the track (much cheaper).

Changes today ?

Electrify at 60 kV AC, double & triple track most lines (back to 1950s), drill more tunnels, develop light weight & streamlined rail cars (aluminum, titanium, carbon composite) and my network of semi-high speed pax & freight rail lines.  Most areas of US are served by two rail companies, try and build a third (perhaps my semi-high speed line).

Build more rail bypass lines around cities (save existing track for local service) and add more grade seperation (see Alameda (spelling) in Los Angeles).  Rail tunnel to bypass most of NYC.

I am intrigued by Swiss plans to build quiet rail cars, making trains quieter.

Change US safety regulations closer to EU & Japanese standards.  Improve signaling, thus allowing more trains/hour on track, better scheduling.  Car tracking & routing is currently improving (bar codes & computers).

Off the top of my head :-)

Best Hopes,

Alan

Took some time to locate the exact essay I was looking for, but this anectodal evidence suggests that the rails themselves can last for a very long time (100+years)
http://krugtales.50megs.com/rrpictale/OWYtrip/OWYtrip_c.htm
scroll down to just above where the second set of pics start to show:

What is this stuff? 65 lb? I am amazed that stuff holds a 425,000 lb loco or a 286,000 lb coal car. It was rolled by Carnegie Steel in 1902.

also, this short story (about halfway down the page) is quite wellwritten, it is the tale about a locomotive, 15 coal cars, a bet and a skilled engineer. One of the more exciting things I have read this week :)
http://krugtales.50megs.com/rrpictale/kiewit/kiewit.htm

The ammeter climbed back to 850 then went right on to 855 and approached 860. I felt it in my butt first, before the ammeter dipped or the chant of the 567 lightened. I slapped the throttle down one notch but it didn't respond quick enough. The SD9 slipped. The wheelslip circuit detected the stumble and cut the load even more.

This site gives a view into the world of american railfreight, always from the engineers perspective.