Hi, yesterday we had the curious situation that there was an accident on an inner-city road that required a full lock of the (four-lane) road in the direction of the accident. To do this, a police vehicle was parked across both lanes at the height of the descent. Shortly after the vehicle was parked there, a novice raced frontally into the vehicle, resulting in injuries and high damage to property. the vehicle must be secured in advance in order to draw the attention of the most dreamy drivers to the immediate following situation?