SOAPBOX is a forum for people with
strongly-held views
WHY SO many digits? The other day I saw
a car go through a red light in front of four or five other
cars and none of us were able to get his number
plate.
After thinking about it I realised that the
reason I was unable to get this person's licence number was
because there was an extra "1" placed in front of the
traditional number plate.
The extra one means that we
now have seven characters instead of six, which means that the
characters have to be smaller to fit on to the same sized
number plate.
If you look at the licence plate of an
older car, you will see that the six-character licence plates
are easier to see as the characters are bigger.
There's another problem. The human brain has the
natural capacity to remember seven plus or minus two items in
short-term memory (that is somewhere between five and nine
items).
It is more difficult to remember more
characters.
Ah, you say, but the first number "1" is
redundant, so really there are only six characters to
remember.
The problem is that you cannot help looking
at this redundant number (which is exactly what it is) because
they placed it in front of the licence plates.
Why
didn't they place it at the end so we wouldn't even have to
look at it? Anyhow, why have we gone to seven
characters?
This is where I am really
confused.
A little mathematics reveals that with four
digits and three letters there are about 180 million
combinations possible, which can cater for over 100 cars each
for every man, woman and child in WA.
My understanding
is that the current licensing system has been around for four
or five years now and we have only just gone from using
licence numbers beginning with 1A to licence numbers beginning
with 1B.
This means that we should get to 1Z in about
100 years and we should get to 9Z in about a 1000
years.
Under the Department of Planning and
Infrastructure's own estimates, in the current system we have
enough licence plates for 1400 years.
This means the
one in front will not become a two until the year 2137, and we
will get to 9ZZZ in the year 3397 (if man is still
alive).
Obviously someone didn't want to have to deal
with this problem again in their lifetime (or for 40
generations, in fact).
But the problem is that people
like the idiot I saw go through a red light got away with
it.
Assuming that somewhere around 100,000 to 200,000
cars are licensed in Perth each year, a licence plate with
three letters and three numbers, which can generate some 18
million combinations, would do just fine.
This would
generate enough combinations for 90 to 180 years. Another idea
would be to use two letters and four digits, with the two
letters smaller and written vertically.
This would be
easy to read, and would generate 6.76 million
combinations.
Another idea is to completely reverse the
licence numbers so that the most significant digits are put on
the left and the redundant digits are put on the right. It
won't matter if we don't get that far when we are reading the
licence plate then.
One could also consider using
names, instead of unrelated letters, as the brain stores them
as a single entry in memory.
THE Department of
Transport is not the only culprit of the numbers
game.
Telstra recently added an extra nine in front of
our phone numbers.
I never understood why it did this.
With eight digits, we now have 100 million combinations of
telephone numbers, which could cater for over 100 telephones
for every household in WA.
Incidentally, New York still
has only seven-digit phone numbers, with a slightly longer
area code (which is easy to remember, or can be looked
up).
Why does Perth need so many digits?
I was
also a bit confused as to why the extra nine was added to the
front of our phone numbers.
Previously we could easily
see which area a telephone number corresponded to. Although
this is still (sort of) the case here, as we can (mentally)
just drop the redundant nine in front, what will happen in the
future when we start to use other digits in front other than a
nine.
We are already starting to use phone numbers in
the same area beginning with a six.
To my mind the only
thing a nine in front will tell us is whether we had a phone
in the year 2000.
Assuming this extra number is needed
(which I suggest it is not), it would have made much more
sense if it was added at the end of our phone numbers so that
the first few digits gave us an indication of
area.
This would have freed 10 times the available
numbers for each current area and surrounding suburbs could be
given similar starting phone numbers.
Dr George Christos is a mathematician and
neuroscientist.
