TALLINN, Estonia, Dec. 27 (Xinhua) -- When does a Christmas card send a shiver down your spine?

When it works like a referee's yellow card during a football match, as in Estonia.

This holiday season, the Estonian police sent out over 700 "black" Christmas cards. The recipients were people with five or more driving offenses during 2017, Reuters reported.

Dispensing with personal greetings, the card bears images of road accident scenes with the text urging the reader to abide by traffic rules.

This year, Estonia witnessed over 40 road deaths.

The Estonian police have been sending such cards since 2011, which has actually helped reduce the number of road deaths.

Drink driving has also declined from 17,920 incidents in 2007 to 6,100 in 2017.