Historically, some road systems were centrally planned while others were simply allowed to develop according to local initiatives. In general, road systems of national interest are better planned nationally. The motive underlying those centrally planned was generally military, to ensure that large numbers of troops could be moved rapidly to trouble spots. This underlay the Roman system, which was unique in that it was not country but empire wide. It also motivated the French system, developed in the late 17th and early 18th centuries, the German (1930's) and the more recent American Interstate system (1950's). The British never bothered and relied on a rather happy-go-lucky system relying on local responsibility and private enterprise, guided, very approximately, by national legislation.
The Romans took their roads very seriously. Although there have been roads of sorts since the invention of the wheel they were the first to plan and construct a sustainable network . It was intended to link Rome to the major cities of Italy and thence to the outposts of Empire. Construction norms were not those of the modern road, which aims at a twenty-year useful life. They built for centuries and many sections are still there today.
Their networks provided many of the services we take for granted now. Travellers could buy road maps and even guides to the many hotels and restaurants. Like today the food was often reputed to be poor, as was the accomodation, so wealthier travellers brought their own.
