Transitory Data
UK rail (and many other) tickets include a magnetic strip.
Magnetic strips can contain 3 data tracks containing respectively 210, 75 and 210 bits per inch (either due to technical reasons or the needs of competitive comittees) (1)
UK rail tickets are 3 3/8 inches wide. Let's assume the edges are dodgy so they have 3 inches of usable data strip. In that case each ticket could hold
3 * (210 + 75 + 210)
= 1485 bits or just over 185 8-bit bytes (2)
A Ticket is slightly chattier than a Tweet.
In 2010-11 757 million non-season ticket rail journeys were purchased (3). Let's assume that these were mostly return journeys which are printed on 2 separate tickets so our nominal journey carries 371 bytes. Let's omit obligatory reservations which are issued on the same stock so have magnetic strips of their own, this being a calculation on the less glamorous side of the envelope.
So last year railways in the UK issued
757 * 371 million
= 280847 million bytes
or 262Gb or thereabouts per year in the UK. Data moving from place to place in the collective travelling pockets of the UK.
That's small by the standards of your favoured, modern and loquatious online community but it is still a large and mobile body unbothered by the niceties of modern telecommunications. Not bad for a technology of the early 1960s.
These magnetic strips occupy a space somewhere between the short online message and the postcard - mobile packets of data in need of re-use once they had done their first travelling duty.
With apologies for the dubious sums.
1) http://en.wikipedia.org/wiki/Magnetic_stripe_card
2) The standards appear to show 7- and 5- bit units but let's allow for parity bits and the like http://www.gae.ucm.es/~padilla/extrawork/tracks.html
3) Passenger journeys by ticket type - table Great Britain 2002-03 Q1 to 2011-12 Q2 (millions) http://dataportal.orr.gov.uk/displayreport/report/html/2cab3179-cd25-44e9-b03...

























