An environmental assessment system for correlating environmental data with traffic data having, a traffic/environment system including a) a traffic count system for obtaining the traffic data of moving objects on a road, and classifying the moving objects into several vehicle types, b) an environmental sensor system including a particulate matter (PM) sensor for measuring PM concentration and/or a carbon dioxide (CO2) concentration sensor, c) a microphone for obtaining sound signals originated from the moving objects on the road, d) a communication device and e) a microcomputer/memory for running computer programs, the computer programs including a function for adding a time stamp showing a time onto the traffic data, and a sever having functions for correlating the traffic data with the environmental data, wherein the traffic count system is arranged to classify the traffic data by referring to the sound signals obtained by the microphone.