Sub-problem 1a:  Traffic Flow Patterns

Flow-Occupancy
Exhibit 4-9 shows the corresponding flow-occupancy relationship for the same lane and peak hour. The classical triangular shape depicted in textbooks is evident, with a positive, linear relationship from (0,0) up to a maximum of (15, 2264) between occupancy and flow for the uncongested conditions and then a downward sloping trend toward (100,0) for congested conditions during queue clearance.

All of these exhibits tell us we have a basic freeway section with typical variations in the flows and the flow conditions. Moreover, from Exhibits 4-5 and 4-6, it is apparent that the volume to select for the peak period analysis is not that obvious. The volumes during the peak hour tend to vary a great deal. In the AM peak hour (7-8:00 AM), for example, the volume ranges from about 200 veh/hr up to nearly 3,500 veh/hr. The average is about 2,000 veh/hr. None of these values seem to be correct for the analysis. The westbound volume during the PM peak hour (4-5:00 PM) range from about 750 veh/hr to 3,800 veh/hr, averaging about 2,000 veh/hr. Again, none of these values seem to be the best choice for a PM peak hour analysis. We can gain further insight into the issues associated with that choice by examining the flow rates associated with the four 15-minute time periods that occur during the AM and PM peak hours on weekdays during the year.