(sometimes the parked cars / bikes are reversed on the few streets with Copenhagen-style bike lanes, but this is rare).
Needing separate lanes for trams, cars, and bikes makes the streets hella wide. But not having separate lanes is even worse, like Sydney Rd in Brunswick where trams can take half an hour to travel a couple of kilometres and cyclists are killed on a monthly basis by people opening car doors and knocking them into traffic.
Every time a tram stops it stops in the middle of the road: all the cars around it also need to stop (and most of the time they do, but not always) and then the people need to get from the centre of the road to the footpath safely.
To fix this the city has been installing large train-style super tram stops, but this takes up even more space and makes it even harder to fit in bike lanes on narrow streets. On Swanston St the bike path actually runs along the tram stop:
so people waiting for trams have to stand behind the yellow line or get taken out by a bike, and bikes have to stop when a tram is taking on passengers. You would think that would be a total clusterfuck but actually it more or less works, although at least once a week a car gets confused and drives down the platform and then falls off and gets wedged, blocking the tram line until it gets towed:
Plus the overhead wires the trams use are super ugly.
On the upside, tracks are more energy efficient and there are ways to do trams without overhead wires (such as in some European old towns) but it’s tricky.
When tracks are built separately from other traffic trams can achieve really high speeds, and the aesthetic footprint is lesser because instead of a fuck-ass wide stretch of asphalt the tram only needs two narrow strips of metal, and the thing between them can even be grass (as it sometimes is in European cities). And trams are more predictable in traffic, enabling the safety margins between them and others to be smaller; you can put a fence in exactly the position where a tram will not hit it, and the other side will be safe for pedestrians or cyclists, but you can’t have buses with only 50cm between them and fragile people, and you most certainly can’t drive a bus 80km/h if it has fences on both sides only 30cm away.
Furthermore, trams are more suitable for underground operation, such as in the Antwerp Premetro or SF Muni, allowing the tracks to be hidden away in the densest places at some cost in the ease-of-access department.
Trams have a significantly greater capacity, and it’s impossible to service important core lines with buses in any kind of a decent mass transportation system (eg. there’s one in Helsinki where they sometimes drive four buses behind each other to have room for all the passengers, and that’s pricey as fuck; little surprise they’re trying to turn it into a tram as fast as they can).
Electric buses are making the air quality part of the equation a bit more equal, so diesel pollution will not be a massive factor for long, but rubber transportation generates significant quantities of toxic dust from the tires and asphalt, whereas trams (metal emissions from the tracks and wheels) might possibly be less polluting.