Variable traffic safety sign for displaying roadbed conditions in response to changes in temperature and humidity

A variable traffic safety sign for displaying roadbed conditions in response to changes in temperature and humidity to inform road users of the possibility of a surface of a road or bridge section being wet or frozen, comprising:

• a general paint applied onto the traffic safety sign for use as a background color;
• a first thermochromic paint formed of a first thermochromic material and applied to develop a first color different from the background color at a first predetermined temperature so as to reveal an outline of a shape formed by the first thermochromic paint distinguishable from the background color;
• a second thermochromic paint for freezing display formed of a second thermochromic material, which develops a second color different from the background color at a second temperature lower than the first predetermined temperature as to fill an inner area the outline formed by the first thermochromic paint with the second color to indicate freezing conditions of the road or bridge section;
• a first humidity indicator paint formed of a material for a first humidity indicator card (HIC) and applied to develop a third color different from the background color at a first predetermined relative humidity so as to reveal an outline of a shape formed by the first humidity indicator paint which is distinguishable from the background color;
• and
• a second humidity indicator paint formed of a material for a second humidity indicator card, which develops a fourth color different from the background color at a second humidity higher than the first predetermined relative humidity as to fill an inner area of the outline formed by the first humidity indicator card with the fourth color to indicate wet roadbed conditions of the road or bridge section,
• wherein the first and second thermochromic paints and the first and second humidity indicator paints indicate freezing and wet roadbed conditions of the road or bridge section via colors distinguishable from the background color, respectively, without using an external power source.