The harsh climate in winter can cause complex road surface conditions

such as damp

snow cover

ice and snow mixed on the road surface

resulting in less friction between the tire and the road surface

which is the direct reason of traffic accidents. The non-contact road surface detection system can effectively distinguish road surface condition and provide early warning signals in time. It has the advantages of low cost

easy installation and maintenance

compared with the contact i. e. buried method. Definition of road surface condition is given

and the non-contact detecting technologies at home and abroad are summarized. Main principles and key technologies are elaborated

advantages and disadvantages are analyzed

future development direction of non-contact road surface detection technologies are prospected.