yep, those roads will completely dissolve in just a month or two without constant maintenance!
http://www.google.com/search?q=Roman+roa...42&bih=585
The asphalt lane in front of my house was paved in 1973 and has been patched once since I moved here 5 years ago. It even has some heavy truck traffic and has held together well. Under present use conditions modern asphalt motorways have a life expectancy of more than 10 years!
Concrete is rated for even longer!
Some of the concrete motorways, with the reduced traffic of a "new dark ages" transport flow, might last for 1,000 years.
At the end of that 1,000 years I might have to shift into 4wd and slow down for the potholes a bit.
With no where to go, no fuel to get you there and nothing to buy once you arrive, travel will take on a new dimension anyway.