"Tadej Brezina" wrote in message
...
I stumbled across this plan (http://www.lrta.org/london-Hounslow.html),
involving a tram from Hammersmith to Heathrow along the A4. They say
that it would reduce traffic on the A4 by 20%, however I understand it
would take up one lane in each direction (33%) of the road capacity,
therefore *increasing* congestion.

Which is simply wrong!

Normal car capacities (calculation guidelines values, real numbers are
significantly higher) are about 2000 cars/lane/hour.
Well let's say, that the cars have very high occupation (3 people per car,
which is way higher than the actual abt. 1,3) then we get a transport
capacity per lane per hour of 6000 persons per lane per hour.
A tram's capacity is abt. 22 thousand passengers per hour [1].

Quite apart from the fact that this looks unbelievably high (22
trams per hour with 1000 pax each, how many pax can you get
in a single tram?) this assumes that you will get this number of
people to transfer mode.

In Britian this seems most unlikely even if you did run a tram
evey 2.5 minutes (which they wont).

tim