Sub-problem 1b - Page 6 of 7

ID# C401B06

Sub-problem 1b: Analysis of the Eastbound Freeway Section

The result for our situation is S = 54.8 mph. If you take this value and divide it into the peak 15-minute flow rate, v_p, then you get the freeway segment’s peak 15-minute average density (passenger cars per mile per lane), which is the basis for assessing the LOS (see Dataset 1):

D = v_p / S = 1,902 pcphpl / 54.8 mph = 34.7 pcpmpl

Where pcphpl means passenger cars per hour per lane, mph is miles per hour, and pcpmpl is passenger cars per mile per lane. The breakpoints in D for level of service are as follows, all in passenger cars per mile per lane: A: 0-11; B: 11-18, C: 18-26, D: 26-35, and E: 35-45. Above 45 is LOS F.

For the circumstances we’ve examined, where D = 34.7, the LOS is a high D, almost E. Since we picked the 90^th percentile value to evaluate, this means that 10% of the time the eastbound LOS in the peak hour is D or worse, and 90% of the time it is better than that.

Three other significant conditions have the following levels of service:

	For the average AM peak hour, where the volume is 2,916 veh/hr, D is 30.2 pcpmpl and the LOS is D (See Dataset 2).
	For the high hour recorded during the short count upon which the AADT is based, the volume was 3,257 veh/hr, D is 33.8 pcpmpl and the LOS is D (see Dataset 3).
	For the heaviest hour observed in 2001, where the volume was 3,483 veh/hr, D is 36.5 pcpmpl and the LOS is E (see Dataset 4).

If we want to more clearly characterize the performance of this location during the peak hour, we ought to evaluate its performance during all of the 256 peak hours (7-8:00 AM on a weekday) for which we have data. This isn’t a reasonable thought from a practical standpoint, but it gives us a way to make an important point.

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