1. photograph the event if possible;
2. Write a brief statement about the event and describe as precisely as possible how to arrive to the location (if there is a correct address, some visible object, distinctive sign and the like.).
3. forward a statement together with photos to the traffic police in your city/town.

WHOM TO CALL: and/or Green Phone service for your county (072 123 456) - the report may be sent anonymously, too.

NOTE: You can always call the service 112, especially if it is a matter of great urgency, and during the weekends, holidays or at night