From: pop@cs.umass.edu ( Robin Popplestone )
Newsgroups: rec.railroad
Subject: DMU's and putting the world to rights.
Keywords: energy-efficient diesel-multiple-unit
Date: 21 Dec 92 19:27:41 GMT
Organization: University of Massachusetts, Amherst
Originator: pop@roo.cs.umass.edu

Dave Pierson writes


<< If traffic MUST be maintained, and one or two cars are all that  is
needed, a DMU is the way to go. If more cars are needed (and MBTA runs
crush loads, during rush hour, on  four and six car trains), then  the
balance for all expenses tilts towards loco haulage: For a DMU, if  an
engine is down, the seats  are idle. For an  engine, if the engine  is
down, the seats stay in service. (The RDC's had "quick change"  engine
facilities built into the design, but even so....)>>

Locomotive haulage for commuter trains has really been obsolescent for
the whole of this century -  essentially the problem is that  adhesion
(despite remarkable improvements of recent years) cannot keep up  with
improvements   in   specific   power   (kilowatts/kilogram),   since a
locomotive is limited  at low  speeds (which means  below 70mph  these
days  for  passenger  applications)   by  wheel  slippage.  Thus   the
advantages listed by  Dave Pierson  for locomotive  haulage are  still
seen to apply  in Europe for  medium speed rail  (e.g. British  Rail's
class 91 electric  BoBo can pump  out its 5  megawatts between 70  and
140mph and comfortably beat the heavier  pair of diesel power cars  of
the previous generation HST). But,  even in Europe, 100 mph  commuting
is the exception.

The earliest  attempt  I  know  of  to  save  locomotive  haulage  for
commuters from  its  inexorable  fate  was c.  1910,  when  the  chief
engineer of the Great Eastern Railway in England, who evidently  loved
his choo-choos, proved to  the satisfaction of  critics that a  0-10-0
tank locomotive could match electric train timings. Nobody thought  to
ask how the mountain of coal that the monster would consume was to  be
paid for.

Now informed opponents of  rail such as  MIT's Alan Altshuler  reserve
their bitterest scorn  for the  locomotive hauled  commuter train,  as
being of all transport modes the  least likely to save energy  (except
perhaps a private  helicopter). Now  I think he  is WRONG  in all  his
analysis, because  what he  does not  take into  account is  that  you
cannot separate  transport from  the society  it serves.  When the  US
after the  war  plastered  itself  with copies  of  Hitler's  gift  to
civilisation,  the  autobahn,  it   committed  itself  to  a   diffuse
demography that has energy inefficiency  as its essence (whatever  its
perceived strategic advantages for  the cold war). So  no one need  be
surprised that it  costs the  US 50% more  energy to  achieve a  given
added value than it  does its competitors. [even  this is probably  an
underestimate - Consider for instance the fact that following a growth
spurt in the  80's and  the collapse of  competition by  the USSR  and
South Africa,  the  US  has  recently achieved  the  highest  rate  of
incarceration in the world - this (together with burglar alarms  etc.)
presumably gets included in  the GNP, but  doesn't contribute much  to
the sum  total of  citizen happiness.  Contrarywise, one  may  suppose
however that Japan's  rather archaic distribution  system does  give a
certain contentment  to the  people involved.  Consider also  how  the
enormous US  expenditure on  health care  produces a  life  expectancy
around that of one of the poorer EEC countries. Probably in some  real
sense, the  US produces  about 50%  of the  value from  each joule  of
energy that Europe does.]

It does  help  to  rebut  the Altshuler's  of  this  world  if  public
transport systems have clear goals of energy efficiency. It also helps
to boost the proportion  of costs recovered in  fares. In Europe,  the
DMU has a humble role to play in this, partly by providing service  to
places so  small  they could  hardly  be called  villages,  partly  by
providing service on lines that have not yet been electrified.

The US, trying to turn  swords into ploughshares, could well  consider
setting up the  kind of symbiosis  between military and  rail uses  of
diesels that  has been  a feature  of the  UK scene.  The military  of
course like diesel engines, because  their soldiers stand less  chance
of being fried when the fuel tank  of their tank is hit. So should  we
all - standard  training for the  British Army is  to demonstrate  how
good a bomb can be made from  an automobile with a few ounzes of  high
explosive strapped to its  fuel tank. Why make  life easy for  rioters
and terrorists? Now the US naturally has some advanced diesel  engines
under development, which could perhaps  usefully be married to  trains
in  various  configurations   (e.g.  one   could  concentrate   diesel
generators but distribute an electrical drive).

Refs: Alan Altshuler  (et al) 1981  "The Urban Transportation  System:
Politics and Policy Innovation",  MIT Press, ISBN  0-262-01055-0(hard)
0-262-51023-5 (paper)
Newsgroups: rec.railroad