I have road lines making 3M a year with goods when the fast lorrys come around. With a train line profits are rarely above 2M and thats serving multiple towns. It takes too long for the industry lines to start producing IMO, if you start with an untouched industry producing 1/25 and you build a line across 5 towns needed a combined 400 goods it takes 30 years for the industry to actually produce that much, so in order for the line to work and be frequent I have these expensive trains running with 3/120 goods at time to these citys making -5m a year for 10+ years. It should pick up production faster IMO!
I aim to keep goods frequency of 5 mins maybe this is too much if I go much higher I find the industry just sit there at 0/25 in my latest attempt, go to forest, go to woodshop, go through 3 towns, I gave up after it sat at 0/25 “line usage yes” frequency 4 mins, rage scrapped the entire line and replaced it with road that was a waste of 10M+ the cost of running 4 trains. for several years.