[cameldrv]

Trains are faster if they're grade separated because they don't have to wait for traffic. Not waiting for traffic also makes them more reliable, especially during rush hour. If you can't rely on the schedule, you have to put padding into your schedule, which makes them effectively even slower. Trains are also faster because they have lots of doors and the passengers are waiting at the same level as the doors, and you're not waiting for people to buy tickets, so the stops are quicker. Since they move faster, you can also run a more frequent service with the same number of vehicles (driver cost is a very large component of operating costs of a public transit system) They're also smoother and so more pleasant to ride. You're usually also waiting for them out of the elements.

[peeters]

The grade separation is a big thing. When I compare taking the bus in Toronto to taking the bus in Ottawa, which has (some) dedicated transitways for buses, complete with dedicated overpasses and bridges, there's a world of difference.

For an example, follow the roads in this satellite imagery: https://www.google.ca/maps/@45.4116853,-75.6640352,489m/data...

[kgermino]

The thing is "They're also smoother and so more pleasant to ride. " is the only thing on that list that's even remotely inherent to trains over buses. Yet you rarely see people arguing to improve the buses so the other things you mentioned aren't an issue.

[cameldrv]

Ok, but if you take a bus and do all of the things I mentioned to it, you end up with a "rubber tire metro", which does exist, and is used in Paris and Mexico city, at least. These are basically indistinguishable from a passenger perspective to a train. The smoothness of trains is really out of necessity. If the tracks weren't smooth, the train would derail.

[tacticus]

Capacity is significantly higher and stop frequency significantly lower allowing a high speed high volume route.