When I first started, I treated passengers like coal: I would wait for a station to be ‘Full’ before moving them. I built a massive bus terminal and sat back, waiting for the profit to roll in. Instead, my station rating plummeted to Appalling and the passengers seemed to just… vanish.
I felt like I was failing at the most basic part of the game. It was frustrating to see a city of 5,000 people producing zero profit for my bus line. I nearly scrapped the whole road network in a huff.
I changed my thinking completely after watching the Master Hellish: Towns & Cities series. I realized that passengers have a ‘shelf life.’ Unlike coal, if they sit on a platform too long, they get ‘bored’ and leave. The problem was my ‘Full Load’ order — it was actually a ‘Profit Killer.’
I switched my buses to ‘No Loading’ or simple ‘Go To’ orders with high-frequency service. Even if the bus was only half full, the constant movement kept the station rating high and the passengers flowing. It turned my city transit from a money pit into a steady gold mine.
Disclaimer: do not expect passengers in buses to be a gold mine… With enough passengers you can do well and in the beginning of a game they are cheap to start with so not a bad idea - just do not think that intercity busses are going to make you rich.
What buses and mail trucks do, however is spur on city growth (not so much with towns since the have a built in lower growth rate). With up to 5 stations in a city the growth rate will be maximum. More than 5 will not cause more growth but will ‘feed’ an airport (see below).
What I usually do is build 4 bus stations and 4 truck/mail stations. Two of the mail stations I join to the closest bus stations- they each pair join to become a combined bus and mail station, essentially so now I have 6 stations total, That meets and exceeds the 5 station threshold but is convenient the way I lay out my stations. They do not service the same areas end end up covering the whole city area.
Later I join an airport with the main station. By then the passenger count of the joint bus, mail, and airport station is getting plenty of passengers and mail. That creates a good way to start a profitable airline. The other stations feed the main station and therefore the airport. Clear as mud?
Clarity Reflection: In the 'Matrix' of OpenTTD, frequency beats volume every time when it comes to people. It is better to have five small buses running a loop than one massive bus waiting to be full. Keep them moving - keep them happy.