Three documents discuss superstitions related to the number 13 and bad luck. The first discusses a study finding higher transport accident injuries on Friday the 13th despite fewer vehicles. The second describes the superstition of crossing fingers for good luck. The third discusses cyclists wearing the number 13 upside down to avoid bad karma if assigned that number in a race.

1. Curse of Friday 13th?
A paper published in the British Medical
Journal in 1993 examined whether
Friday the 13th is bad for your health.
The researchers found that, despite
there being fewer vehicles on the road
on Friday the 13th, there were more
injuries from transport accidents.
However, whilst emergency admissions
due to accident or poisoning were found
to be higher on Friday the 13th than on
Friday the 6th, the differences were not
statistically significant.
Fingers crossed!
Crossing your fingers is a popular and
enduring superstition to bring good
luck or show support in many western
countries. Pagans believed that the
cross (made by two people crossing
index fingers or their own index and
middle fingers) was a powerful symbol
and that at the intersection there was
a concentration of good spirits. They
could therefore wish on the mid-point of
the cross to fulfil their wishes and fight
off evil spirits. But beware: in Vietnam,
crossing your fingers is seen as an
obscene gesture!
Race number ‘ ’
Professional cyclists are a
superstitious bunch, perhaps with
good reason, as so many aspects of
bike racing are out of a rider’s control.
The tragic events on Friday the 13th
July 1967 during the 13th stage of the
Tour de France when Tommy Simpson
died on the ascent of Mont Ventoux
have done little to reduce superstitions
in the peloton. To try and ward off bad
karma, if given the race number 13,
riders will often wear it upside down.
Team Consulting
Insight Issue 13
Is bad luck created through oversight?
Issue 13 of Insight – is it unlucky, a disaster?
Jess, Matt and Chris look at bad luck.
Unlucky for some!
By Jess Fox,
Matt Chandler and
Chris Hurlstone
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2. Fluttering in the breeze
The Tacoma Narrows Bridge collapse is
particularly famous amongst engineers.
The suspension bridge in Washington
state opened in 1940 and collapsed
spectacularly in the same year.
Moderate winds (under 40mph/64km/
hr) generated huge twisting oscillations
in the bridge deck that ultimately tore it
to pieces. The cause was a phenomenon
called “aeroelastic flutter”, in which
aerodynamic forces generate and feed a
resonant vibration in the structure.
Killed by Code
The Therac-25 was a computer-
controlled radiation therapy machine
that was withdrawn from the market in
1987 following an intensive investigation
into over-dosage treatments, which
led to the death of four patients and
life-changing injuries to two others.
Two software bugs were found to be the
cause of the malfunctions, but perhaps
more fundamentally, the hardware
interlocks present in earlier systems had
been replaced with computer control.
The poor system design, minimal risk
and fault analyses, and inadequate
testing of the Therac-25 has had a
significant influence on the design and
development processes of medical
devices today. ENDS
Always check your units
July 23rd 1983. An Air Canada Boeing 767
crash landed at an air force base/motor-
racing track in Gimli, Manitoba, having
glided down from 12,000 metres after
running out of fuel. The main cause was
that ground staff and the pilot used the
wrong units when re-fuelling, calculating
the fuel on board in pounds rather than
kilogrammes and hence taking on 4,900
litres rather than the 20,000 they needed.
They were unlucky for four reasons:
Canada was new to the metric system
and flight paperwork still featured
imperial conversion factors; the 767 was
only four months old and checklists were
still in flux; fuel gauges were faulty; the
767 was the first plane to have a pilot
and co-pilot, but no flight engineer, who
normally checked the fuel. However,
the captain was an experienced glider
pilot, and all 61 passengers (plus motor
racers) walked away uninjured!
Unlucky for some
In many countries, the number 13 is
commonly associated with bad luck,
but it isn’t the only ‘unlucky’ number.
In China, the pronunciation of ‘4’ is
similar to that of ‘death’ or ‘decease’.
Many buildings do not have any floors
starting with 4, and patients avoid
having surgery on a date containing
a 4. VIXI (an anagram of ‘17’ in Roman
numerals) is Latin for ‘I have lived’ and is
commonly found on headstones in Italy.
Consequently, the number 17 is unlucky
and is associated with tempting death.
Alitalia misses out row 17 on its aircraft.
Omen-ous thunderstorms
Ancient cultures believed that thunder
and lightning were messages from the
gods. The Romans feared thunder and
believed that hearing it on your right
side was bad luck. Depending on which
day of the week thunder was heard, it
could signify anything from the death
of a beggar to widespread death. In the
Middle Ages it was thought that thunder
signified demons in the sky and dark-
arts practitioners specifically performed
ceremonies during thunderstorms,
believing that evil spirts were close to the
Earth. However, the Victorians believed
that thunder at a funeral signified a soul
being accepted into Heaven.
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