[SystemSafety] Mid-19th c railways and "gravity models"

[Peter Bernard Ladkin]

I just came across a paper which might interest many here although it is not about safety. It is
about planning railway routes back 150 years ago. It is written by Andrew Odlyzko, a mathematician
known for his work in cryptology and number theory, who interests himself also for early railway
history, which he calls "by many measures the greatest technology mania in history".

Apparently there are things called "gravity models" of social interaction. The simplest says that
people interact in proportion to their number, and in inverse proportion to the distance between
them, and has been attributed to the US economist Henry Carey in 1958. Odlyzko says that the Belgian
civil engineer Henri-Guillaume Desart used one a dozen years earlier, in 1846, to analyse railway
routing. But his work was not used.

At that point, the prevailing understanding seemed to be that people would want to travel between
centres of population some distance from one another. Gravity models suggest, in contrast, that most
journeys are in fact more local. This may not be news to anyone who uses the UK south-east network,
nor indeed to anyone who stands on a platform at Bielefeld station between 6 and 8 in the morning.

Odlyzko notes that the cumulative investment in railways amounted to about 60% of UK GDP in 1914, so
any better way of routing, resulting in more, and more effective, rail travel, would have affected
the overall economy hugely. Not to speak of giving Dr. Beeching much less work to do in 1963.
http://www.dtc.umn.edu/~odlyzko/doc/mania09.pdf

The paper is advertised in Risks Forum 28.24, which came out today (actually yesterday evening in
the US). Odlyzko has quite a lot on the history of the rail technology bubble at
http://www.dtc.umn.edu/~odlyzko/rrsources/index.html

PBL

Prof. Peter Bernard Ladkin, Faculty of Technology, University of Bielefeld, 33594 Bielefeld, Germany
Tel+msg +49 (0)521 880 7319  www.rvs.uni-bielefeld.de