The “CH” sticker that Swiss drivers must legally put on their vehicles before entering another country is required under the 1968 international convention on road traffic.
Under the convention, any vehicle driven outside its home territory must display country initials made up of one to three latin characters. Most European plates incorporate the required identifying characters. But the white Swiss cross in a red crest does not meet the rules so Swiss licence plates must be supplemented with a “CH” sticker.
Watch the size of your “CH”
Some Swiss drivers have opted for unusually small “CH” stickers. But many of these don’t meet the rules. It’s possible that some with tiny stickers may be intentionally failing to meet the arcane rules as a form of bureaucratic defiance. However, others may be unaware that their small sticker does not measure up to convention standards.
According to annex 3 of the convention, the letters must be at least 8 centimetres high with at least 1 centimetre thick strokes. They must also be black on a white horizontal egg-shaped background measuring at least 17.5 centimetres wide and 11.5 centimetres high.
The measurements are different for nations that choose three letters and the ellipse can be vertical if there is only one letter.
In practice the authorities in foreign countries respond with differing degrees of diligence to “CH” sticker delinquents. Italian police seem to be the most zealous enforcers, while the French and German police rarely do anything.
Note: “CH” stands for Confoederatio Helvetica, Latin for Swiss Confederation.
1968 international convention (in English)