Extraordinary scheduling

When I was editing the International Abstracts in O.R., there were numerous research papers dealing with scheduling problems, and I sometimes wondered if some of the more theoretical ones deserved to be published;  in fact one of my colleagues commented that many academic papers about scheduling a job shop were written by authors who had never seen a job shop!  Certainly, I came across many that made assumptions which were most unlikely to occur in practice.  However, the research on theoretical models for scheduling has helped the development of various O.R. techniques, so the work is not in vain.
One of the great pieces of scheduling in engineering history was the conversion of rail  track from broad gauge to standard gauge. In Britain the Great Western Railway (GWR) designed by Brunel, pioneered broad gauge from 1838 with a gauge of 7 ft 0 14 in (2,140 mm), and retained this gauge until 1892.  In one weekend, the majority of the network was converted to standard gauge 4ft 8 1/2in (1435 mm)  Brunel had believed that the broad gauge would give faster, more stable trains.  (Incidentally, on Exeter Quay, there is still a short length of dual gauge track, with three rails, allowing both Brunel's broad gauge and standard gauge trucks to use the quay.  Also, as a matter of trivia, standard gauge is supposed to be the average separation of wheels on carts measured by George Stephenson -- a distance that depends on the need for two horses to be harnessed to the cart.  This is close to the distance between ruts in Roman towns and forts, from 2000 years ago.)
Just imagine the effort needed to co-ordinate the manpower, tools and equipment over hundreds of miles of railway track!  In 21st century Britain, railway engineering is carefully scheduled but there are no feats to compare with what happened that weekend in 1892.

I was reminded of this feat of engineering scheduling when I read about another Brunel-related railway.  He was involved with the engineering of the line from Plymouth to Tavistock.  On that line, there was a spectacular viaduct, the Walkham viaduct.  It was built with stone piers and wooden cantilevers, and was 367 yards long and 132 feet high.  In due course, in 1910 the wooden structure was replaced with iron/steel girders, and according to "The Industrial Archaeology  of Dartmoor" by Helen Harris, it was a proud local boast that the changeover was done so skilfully by the workmen that no trains had to be stopped and the normal service could run all the time.  As I read this, I mused about such scheduling.  It would be very impressive -- there was no theoretical model or research paper about it!  There's no evidence to support that story of careful scheduling that I can find using Google, and I wonder whether the local story is a myth bringing together the conversion to standard gauge and the reconstruction of the viaduct.  The viaduct was demolished in 1965.  A new bridge has been built this year to carry a cycle track that follows the route of the railway line.

Nonetheless, it is a reminder that engineers do scheduling all the time, and their scheduling is authentic. 


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