Someone I know actually does this. “It helps exercise the brain”, she says.
When the traffic’s at a crawl
And you’ve hardly moved at all,
Do some sums with number plates. Here’s how it’s done:
To each letter (A, B, C . . .)
Give a value (1, 2, 3 . . .),
Tot ’em up, then add the numbers, one by one.
It’s a harmless mental test
That will leave your friends impressed
And amazed at skills they didn’t know you had.
Either that, or else they’ll mutter
Sotto voce, “She’s a nutter –
All the stress of driving’s sent the poor girl mad”.