The Gronk
Colon Pounder
Did you miss the last line of my post when I pointed out that although accurate it doesn't make for a good game mechanic?<snipped for space>
The Roman's were the first to standardize an army although the same algorithm is used by modern infantry. If you're in Europe you'll find the cities and castles are often around thirty miles apart, that was because of the same calculation.
When it comes to vehicles you have until the gasoline deteriorates before motorized transport become useless. With bicycles you'll need to find a steady supply of fresh tyres, chains, gear-cassettes and cables. Your best option will probably be horses after the first year or so.