The traffic accidents of expressway are frequent and serious, which pose a great threat to the personal safety of freeway drivers. The function of the guidance device set up on the expressway is single, and the induc- tive effect is not strong. Aiming at the above problems, a new type of intelligent photoelectric contour was de- signed, which can carry out the function of traffic flow density warnings, traffic accident alarm and traffic guid- ance in congested section of expressway. With the traffic accident dredging theory, the traffic density and the in- fluence range of the accident would be calculated under the condition of road congestion or accident. Combined with the level of highway service, flashing alarm for drivers in the range of accidents would be carried out which can reduce the occurrence rate of secondary accidents effectively.