this used to happen to me until i got some really good music c/d s and forget about looking at number plates , like some bob marley also waht could help is getting soem eye drops and put in you eye befor you drive it makes the eye burn and you have some think else to foucs on
Even if you are not good at maths you may just have an affinity for numbers and patterns of numbers or letters. I do similar things when I drive somewhere.
Join the club. I read license plates, bumper stickers, road signs, store signs, anything to occupy my mind for a few seconds. And I get lots of laughs out of them.
Try concentrating on the driving.
just so long as your not reading / answering questions on EP while your driving.....