Number plate characters that get misread
A plate read off a moving car, a dashcam frame or a car park camera is a set of guesses, and the guesses are predictable. You do not have to pick between them — you can search all of them at once.
Shape confusions
Plates fitted since September 2001 have to use a standard typeface, Charles Wright, drawn to keep these characters apart. What is left is the hard core: pairs that stay ambiguous at a distance, at an angle, or through a phone camera at dusk.
| Read as | Might have been |
|---|---|
0 | O |
0 | D |
0 | Q |
1 | I |
1 | J |
2 | Z |
4 | A |
5 | S |
6 | G |
8 | B |
Every pair works both ways: if you wrote down an S it
might have been a 5, and the search treats the two
readings as equally possible.
Dirt, damage and wear
A second set has nothing to do with the typeface and everything to do with the state of the plate: a letter losing a stroke or gaining one through wear, a screw cap sitting in a bowl, road film closing a gap.
| Read as | Might have been | Why |
|---|---|---|
R | B | A damaged bowl, or a lost leg |
P | B | A missing lower bowl |
C | G | A G whose crossbar is obscured |
7 | T | The crossbar angle, at distance |
S | 8 | Dirt closing the loops of an S |
These sit behind a wider setting rather than the default one. Every confusion of that kind is physically real — which is exactly why realness could not be the bar for including one. These five were chosen by measuring the extra noise each cost against the plates it recovered on the full record.
The plate format rules most wrong readings out
This is the part people do not expect, and it does most of the work. A UK registration has a shape, and the shape makes most misreadings impossible rather than merely unlikely.
On a current-style mark the third and fourth characters are always
digits and the rest are always letters. So a 2 you
noted in the sixth position cannot be a 2 at all: that
position takes a letter, and the letter it is mistaken for is
Z. The reverse holds too — a Z in the
fourth position must be a 2.
| You typed | Readings that survive | Why |
|---|---|---|
HY22LZA |
HY22LZA |
Already well formed; nothing to fix |
HY22L2A |
HY22LZA |
Position 6 must be a letter, so 2 reads as Z |
HY2ZLZA |
HY22LZA |
Position 4 must be a digit, so Z reads as 2 |
Two exclusions in the memory tag do more of the same for free:
I and Q are
never issued in a region
code, so a typed I at the front is almost
certainly a 1 and a typed Q almost
certainly a 0.
The practical consequence is that a full plate you typed correctly costs nothing to widen: there are no other valid readings, so it expands to itself and the results are the same.
Lookalike or wildcard?
They answer different problems and it is worth keeping them apart.
-
?— a gap. "I did not see this character." It matches anything, and it costs you a fixed character against the two-character minimum. - Lookalike — a doubt. "I saw it and I might have read it wrong." It matches one of a small set, and it stays a fixed character, so it does not weaken the search.
That difference is why an uncertain plate is better typed than
blanked. HY22 LZ? throws a character away;
HY22 LZ5 with lookalikes on keeps it and searches for
the S as well.
Using it
The setting has three positions. Off searches what you typed. On covers the shape confusions in the first table. Wider adds the dirt-and-damage set.
Widening never loses you a match — turning it up can only add readings, never remove ones a narrower setting would have found. So the sensible order is: run it off, and if nothing comes back that fits the car you saw, turn it up rather than starting again with a different guess.
It combines with everything else, which is usually what finishes the job: a partial pattern, the colour, and the marque, with the uncertain characters widened.
Common questions
Is it a 0 or an O on a number plate?
Position answers it. On a current-style plate the third and fourth characters must be digits and every other character must be a letter, so a round glyph in the middle is a 0 and a round glyph anywhere else is an O. The letter O is also never used in a memory tag, which settles the first two characters as well.
Which number plate characters are most often confused?
0 with O, D and Q; 1 with I and J; 2 with Z; 4 with A; 5 with S; 6 with G; and 8 with B. Those are shape confusions that survive the Charles Wright typeface at distance or through a camera. Dirt and damage add a second set: R, P and B for each other, C for G, 7 for T, and S for 8.
How do you read a number plate from blurry CCTV footage?
Do not try to resolve every character. Write down the ones you are sure of, mark the rest as uncertain, and let the plate format rule out the impossible readings — it eliminates most of them for free. Then search every remaining reading at once rather than guessing at one and running the search again.
What is the difference between a wildcard and a lookalike search?
A question mark says you did not see the character at all, so it matches anything and costs you a fixed character. A lookalike says you saw it and might have read it wrong, so it matches one of a small set and stays a fixed character. Use the wildcard for a gap and the lookalike for a doubt.
Searches to start from
A plate typed correctly costs nothing to widen.