Dominic wrote:

: 1. Buses are as fast as trams - even with diesel engines. If Croydon
: trams ran long sections on the road mixing with cars, or if London
: buses ran on a proper network of properly enforced bus lanes, that
: would become clear.

However, a network of bus lanes costs almost as much as a network of
tram tracks. Combine that with the lower capacity of buses, and you
get a rather cost-inefficient system.

: There's nothing wrong with rubber tyres - they
: allow you to apply greater tractive and braking forces. That's why
: many Paris Metro trains have them.

AFAIR, a lot of political lobbying by the Michelin company was also
involved. Note that rubber-tyred metros aren't that common outside
France.

: 4. Diesel buses are more environmentally friendly than electric trams.
: Although buses produce more pollution at the point of use, trams
: produce more pollution overall - the electricity they run on has to be
: produced somewhere, and it's been through a lot of inefficient energy
: conversions by the time it reaches the tram.

However, it's far more efficient to filter the exhaust fumes of one power
plant than those of several hundred diesel buses.

: 6. One final point - buses require no fixed infrastructure to be built
: on their route. You can run them on the road - brilliant! If there are
: roadworks, you drive around them!

This is a drawback as well as a feature. As one reader on m.t.u-t put it,
"buses can flee". If the local bus company decides to change routes, you
might lose your connection within weeks.

.... Martin