White handkerchiefs and blue road markers warn drivers of breakdowns and icy conditions

A white handkerchief, towel or similar cloth tied to a parked vehicle's external mirror signals a technical breakdown or an urgent health problem for a passenger. The practice, originating in the United States in the 1950s, has spread across Europe; in some countries it is formally recognised in traffic regulations. Other drivers are advised to give way and allow the vehicle to pass so emergency services can reach it quickly.

A blue road post, often installed on bridges, shaded curves or fog‑prone sections, serves as a visual cue that road conditions may deteriorate rapidly, especially due to early ice formation. The marker does not impose a speed limit but urges drivers to reduce speed, increase following distance and stay alert for slipping hazards. Ignoring the warning can lead to longer braking distances and loss of control.

Both signals aim to improve safety by providing early, non‑verbal alerts to motorists and traffic police, helping prevent accidents on potentially hazardous road segments.