THE EFFECT OF VARIABLE ROAD CONDITION WARNING SIGNS

The Finnish National Road Administration launched the experiment of variable road condition warning signs during the winter of 1993 - 1994. The results showed that the sign warning about slippery road conditions reduced the mean speeds. In addition, the variable safety margin sign extended the headways and reduced mean speeds. The experiment was continued during the winter of 1994 - 1995. The signs were tested at four sites. This study was designed to investigate the effects of the variable signs on vehicle speeds and headways, and the persistence and duration of the effect. In addition, the understanding of the sign was studied, and user experiences were noted. The signs used in the experiment were variable road condition warning signs equipped with an additional snowflake sign or without a snowflake, and a variable safety margin sign of an individual safety margin recommendation between the illustration of two cars. Both of the signs changed driver behaviour into a safer direction.