SOME CHARACTERISTICS OF PEAK PERIOD TRAFFIC

A TRAFFIC SURVEY IS DESCRIBED WHICH ANALYZES THE TYPE OF SITUATION WHERE (1) AN URBAN HIGHWAY ROUTE HAS BEEN CONGESTED AT PEAK PERIODS FOR MANY YEARS, (2) A SUBSTANTIAL ADDITION TO ROAD CAPACITY IS SOON TO BE MADE, (3) A RESTRAINING LIMIT ON TRAFFIC GROWTH WILL THUS BE REMOVED, AND (4) THE CHANGE CAN BE EXPECTED TO ALTER PEAK-PERIOD TRAFFIC FLOW RATES. THE OBJECTIVE IS TO DETERMINE HOW HIGHWAY IMPROVEMENTS WILL AFFECT THE CAPACITY STANDARDS USED IN THE COURSE OF PLANNING FOR THE URBAN PEAK DEMAND. THREE SITES IN THE SAN FRANCISCO-OAKLAND BAY AREA WERE SELECTED FOR THIS STUDY. THE FOLLOWING FIELD STUDIES WERE CONDUCTED: (1) TOTAL VEHICLE VOLUME COUNTS, (2) VEHICLE CLASSIFICATION COUNTS, AND (3) VEHICLE OCCUPANCY COUNTS. OTHER FACTORS THAT AFFECT TOTAL VEHICULAR TRAFFIC VOLUMES IN PEAK PERIODS ARE PRESENTED: (1) THE PROPORTION OF HEAVY VEHICLES, (2) THE OCCUPANCY OF AUTOMOBILES, AND (3) PUBLIC TRANSIT RIDING. THE PEAK PATTERNS OF VEHICLE MOVEMENT ON HIGHWAY FACILITIES ARE SHOWN WHEN UTILIZED TO THEIR FULLEST CAPACITY OVER LENGTHLY TIME INTERVALS DURING THE REGULAR MORNING AND EVENING URBAN COMMUTER RUSH PERIODS. VEHICLE CONGESTION HAS CAUSED CONSIDERABLE USE BY PASSENGER CARS OF INFERIOR ROUTES. STALLS AND DELAYS ASSOCIATED WITH INTENSE VEHICLE CONGESTION ARE SHOWN TO SPREAD THE PEAK BY CAUSING SPORADAC QUEUEING OF CARS. THE PEAK PERIOD DATA SUGGESTS THAT EXTREME CONGESTION TENDS TO SHIFT TRAVEL IN SOME TRIP-PURPOSE CATAGORIES.