Not joking this time, but I do agree with simonmd … with conditions.
In the early years he is correct, there were no specialty vehicles or companies, few of which were providing specialty delivery to one customer, oil and gas was delivered in barrels and loads of coal and iron ore were transported in crates loaded on the same flatbeds.
But around 1900 that started to change (real word, not TF), bulk oil carries started to appear, bulk haulers started to show up, and the volume increased so much its doubtful any company getting a contract to haul coal would use the same trucks to haul iron ore.
With that said it would make sense to let any lorry carry any load up until around 1920, then you would need to have segregated routes.
The same could be said with trains, I watched many loaded coal trains snake out of the mountains of West Vergina, and many empties climb back up, I cant think of any reason the railroad would use the same gondolas for iron ore. But before 1900 demand was low enough to allow swapping cars to a different route, to carry different loads.
So that leaves us with implementation, do we ask the programers to provide a separate set of rules governing loads for the first 50 years, then the rules that are used for the remaining 170 plus years?
Naaa, it’s a game, just a new challenge for us to figure out.