irc wrote:What can trams do that buses can't do?
They can carry more people (or freight) at higher speed for less energy, due to the lower rolling resistance of steel wheels on steel rails; just like velodromes use polished wood rather than tarmac. Also due to not needing steering. Of course, there are disadvantages as well.
The zero emissions (at point of use) plus is negated when they are sharing the streets with other traffic, especially buses.
How is it negated? Replacing a diesel-burning bus with a zero-emissions at point of use electric tram means those diesel fumes are not emitted on to that street. Obviously the same advantages apply for an electric (or hydrogen fuelled) bus, car or lorry.
Otherwise buses built to offer the same seating space as trams would have the advantages of being able to operate both on exclusive routes where appropriate and shared streets where appropriate.
It would be very difficult to build a bus to carry as many people as a tram. It would have to be multiply-articulated; a 'super bendy' bus! One advantage of railed transport is that you can add more coaches with increase in turning circle.
They wouldn't have needed the 3/4 of a £ billion spent on the Edinburgh system much of which was for digging up ancient streets to move utilities - not needed for bus systems.
True, although the Edinburgh trams were a complete balls up due to local political reasons.
Any minimal speed advantages for trams are due to dedicated routes.
Possibly. Also to traffic laws giving them priority at junctions (though not in UK I think) and dedicated signalling even on shared routes. Electric traction, which gives better acceleration from low speeds than internal combustion engines, might also be a factor; but of course is not necessarily limited to trams.
You don't need a bus running on rails to have separate routes when appropriate.
No, you don't, but building a separate system with rails and OHLE is a pretty clear commitment. Once the rails are down, they're likely to stay down, whereas bus lanes come and go at the whim of local authorities.
Another tram speed advantage is the limited stops. Conventional city buses make the mistake of having stops so close together the bus can be stopping every couple of hundred yards. That is easily changed.
Every couple of hundred yards does sound very close. Where are they that tight? But there needs to be a balance between reducing dwell times and maintaining usefulness. A transport system that stops too infrequently is no good either. Having parallel stopping and express services is probably the way to go.
And buses don't need tramlines to cause cyclist injuries and deaths.
True.
Another point against trams is the rails can impede road maintenance and more so repair/installation of underground utilities. Coordination between departments (highway, water, etc) and private companies (cable, phones, etc) is necessary.
On the road, trams have the advantage of usually being narrower than buses.
A neglected form of transport is trolley buses. These have the advantage of electric traction with the relative flexibility of rubber tyres. It's much easier to just rig up the OHLE than install rails in the road surface. But those same rubber tyres mean increased energy costs and maintenance compared to trams, though still a lot cheaper to run than diesel buses.