A NEW LOOK AT THE TRAFFIC ASSIGNMENT PROBLEM

TRAFFIC ASSIGNMENT MODELS IN USE PRESENTLY ASSUME THAT THE COST OF USING A LINK IN A NETWORK IS THE SAME TO ALL THE USERS OF THE LINK. THERE IS NO DOUBT THAT THIS ASSUMPTION DOES NOT CORRECTLY DESCRIBE THE ACTUAL SITUATION. FOR EXAMPLE, THE VALUE OF TIME AND THE OPERATING COST OF THE VEHICLE, TWO OF THE COMPONENTS OF THE COST OF TRAVEL, ARE NOT THE SAME TO ALL THE USERS. THE EXISTENCE OF TRAFFIC ASSIGNMENTS WHEN THE ABOVE ASSUMPTION IS NOT MADE IS EXAMINED FOR SOME VERY SIMPLE NETWORKS. WE SHOW THAT STABLE TRAFFIC ASSIGNMENTS EXIST AND THAT THESE ASSIGNMENTS ARE QUITE DIFFERENT FROM THE ASSIGNMENTS OBTAINED WITH THE PRESENT MODELS. (A)