|
Sub-problem 1a - Page 4 of 7 |
ID# C401A04 |
Sub-problem 1a: Traffic Flow Patterns
Peak Hour Factor
There are always other questions about the performance of such facilities
such as the relationship between hourly volumes and the
peak hour factor,
speed-flow relationships and flow-density relationships.
Exhibit 4-7 shows the relationship between the hourly volumes and the peak hour
factors. The data for the entire year are again plotted. The westbound
direction is shown, and the eastbound plot is nearly identical. The average
value for the peak hour factor tends to increase as the volume increases.
There’s more variation in its value at low flows than at high flows. It ranges as low as 0.25 (that means
there was flow in only the peak 15-minute time period) and it spans up to
1.0 for almost all volumes.
The data points associated with a PHF of
0.25 are likely to be outlier points, since this is an unlikely condition to
occur on a freeway with the nature of location of Alternative Route 7; more
likely, these data points reflect time periods when the automatic traffic
counters were not working properly, or the westbound lanes were closed
because of an incident, or some similar situation. So too with the few data
points that seem to suggest a PHF slightly greater than 1.0 since, by
definition, such a condition is not possible. Nevertheless, with such a
preponderance of data, the overall character of the relationship that exists
between PHF and hourly volume is clear.
