THE MODEL USED BY ELSE, REPORTED IN THE JOURNAL OF TRANSPORT ECONOMICS AND POLICY (1982), DOES NOT DEAL SATISFACTORILY WITH OTHER THAN 'SHORT' ROADS. THE AUTHORS SUGGEST THAT LONGER ROADS CAN BE CONSIDERED BY DIVIDING THEM INTO SHORT STANDARD LENGTHS. IT IS ASSUMED THAT THE INTRODUCTION OF AN ADDITIONAL UNIT HAS NO EFFECT ON TRAFFIC AHEAD OF IT BUT ALTERS THE DENSITY, FLOW RATE AND TRAVEL TIME FOR ALL TRAFFIC FOLLOWING IT. THE MODEL CAN THEN BE APPLIED SEPARATELY TO EACH SEGMENT TREATING THE OVERFLOW OF ONE SEGMENT AS THE INFLOW OF THE NEXT. HOWEVER, AS THE MODEL IS SET UP, THIS PROCEDURE CAN YIELD DIFFERENT RESULTS ACCORDING TO THE NUMBER OF SEGMENTS CHOSEN. THE OPTIMUM LENGTH OF SEGMENT IS ULTIMATELY EMPIRICAL BUT A METHOD OF ADOPTING ELSE'S MODEL IS SUGGESTED. IT IS ANTICIPATED THAT FOR EACH SUCCESSIVE ROAD SEGMENT THE OUTFLOW PROFILE WOULD BE FLATTER AND HAVE A LONGER TAIL THAN THE PRECEEDING SEGMENT. TYPICAL PROFILES OF OUTFLOW RATE AGAINST TIME ARE DERIVED FOR UP TO THREE SEGMENTS.
Abstract