More frequent is usually quite the problem because while the vehicles are just a matter of cost, the staff isn't. Driving any large vehicle is a stressful job

More frequent is usually quite the problem because while the vehicles are just a matter of cost, the staff isn't. Driving any large vehicle is a stressful job and there's always a shortage of people willing to do it. Of course this implies that the larger the vehicle the better, so rail comes to mind, but that it turn requires infrastructure. Overall it's a hard problem to solve. Then how did the Europeans manage to do it? They had to. There's literally no other option for a region that doesn't have abundant oil resources.