[sustran] Re: fwd: MRTS Thane

[Kerry Wood]

Dear Friends

I am far from being a railway expert but I can at least give an opinion on
Professor Dhingra's track gauge problem for Mumbai (Bombay).


1       Use 4 ft 8.5 ", only 1435 mm and nothing but 4 ft 8.5".

2       Ignore rule (1) only if there are cost advantages in going down to
metre gauge (unlikely for 40 000 passengers/ hour one way) or if
inter-operability is a deciding factor.


Standard gauge - 1435 mm - does not seem to limit railway size or speed. It
is used by the European high speed trains and the Australian iron ore
railways. The South Africans have shown that even 1067 mm track can handle
very heavy trains.

Loading gauge is a different matter, and for a busy system, wide vehicles
may be a good choice.

Broad gauge - 5 ft 6" (1676 mm) - will impose large curve radii on a
system. Light rail in the UK uses a minimum curve radius of 25 m, but the
European metre gauge systems are perfectly happy to go down to 18 m - and
if you think of a parallel axle bogie on curved track, those two figures
are geometrically equivalent. So is 29 m for 1676 mm track. A busy and fast
system will normally use much larger radius curves on the running tracks,
but may not want to be forced to use them for crossovers, sidings and the
depot. Curve radii are generally larger or much larger on systems without
street running - 6 km is a tight turn on very high speed rail running
tracks.

A key factor is that standard vehicle designs are much cheaper than a
special design, especially if the initial order is small, and there are no
standard designs for 1676 mm gauge. Local manufacturers may prefer broad
gauge because they are used to it and overseas competitors are not, but
they may in the end be better advised to develop something more marketable
overseas - perhaps in collaboration with an overseas company.

So to come back to rule (2), if running metro trains on existing broad
gauge track is necessary, or may in future be necessary, broad gauge has to
be the answer. But if broad gauge running is merely convenient, such as
sharing a depot or overcoming vehicle delivery problems, then the 1435 mm
standard gauge is the way to go. Dual gauge track may be an option in some
places, such as a depot access track. And if broad gauge is merely thought
better, forget it.

Here in New Zealand we are pushing (or hoping) for lighty rail in our main
cities, and I expect that we will be able to use standard metre gauge
equipment, with the wheel rims modified to run on our 1067 mm (3 ft 6")
track.


Best wishes, Professor, with your studies.




Kerry Wood MIPENZ, MCIT
Transport Consulting Engineer
Phone/fax + 64 4 801 5549  e-mail kwood at central.co.nz
1 McFarlane St  Wellington 6001  New Zealand