>>888509>Buses are just more flexible overall, cheaper to purchase and run (and so can be replaced more often), dont require extra infrastructure exclusively for them, are easy to reroute momentarily and modern engines are quiet and relatively clean.It also has very different uses. Bus lines that are greatly used (especially off peak hours) are inefficient compared to light rail.
While buses can be rerouted, they also require more maintenance, carry less people, and require more fuel. They are also objectively dirtier than light rail as at least in my country all light rail is electrified. While engines can be rebuilt, that's not inherently a good thing as electric vehicles usually have a longer service life. From a pure cost perspective, there's no reason to use buses if you live in a dense area where bus systems are nearing capacity.
Point is, buses and light rail have different uses and excel in different areas. Buses are great for suburbs. They aren't great inside large cities, and oftentimes are inferior in connecting one large city to another. The whole point of a "transit network" is to unify multiple transportation modes inside a single system.
