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Q2 Z2,(Q2) Z2(Q2) - Institute for Water Resources - U.S. Army

Q2 Z2,(Q2) Z2(Q2) - Institute for Water Resources - U.S. Army

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Table 5.1<br />

STATISTICAL ANALYSIS OF TRIP TIMES AND DELAY TIMES<br />

FOR 100 UNIT TRAIN MOVEMENTS<br />

.<br />

Predicted Actual<br />

1 Delay<br />

1 Trip Time 1 Trip Time 1 Time<br />

1<br />

! (hours) i (hours) (hours)<br />

1 I<br />

Range . 7.17 - 9.41 1 8.42 - 22.58 ! 0.61 - 14.32<br />

Mean 8.15 1 12.13 4.14<br />

I<br />

Standard Deviation' ._ _i ' 0 ' 47<br />

! 3.26 i 3.92<br />

SOURCE: Midwestern Railway which requested not to be<br />

identified.<br />

An estimate of the average delay time per train is 4.14 hours<br />

<strong>for</strong> the 100 sample movements. The standard deviation is large rela-<br />

tive to the mean, however, indicating, as does the range of actual<br />

trip times, a great dispersion from the mean. .Un<strong>for</strong>tunately, the<br />

data did not disclose the nature of the delays, and it was impossible<br />

to deduce delay-causes except <strong>for</strong> a few cases. Based on an examina-<br />

tion by railroad personnel of some of the very large trip times, it<br />

can be concluded that some atypical delays occurred, e.g., a derail-<br />

ment. Removing these observations from the sample reduces the mean<br />

delay time to 3.85 hours and the standard deviation to 3.09 hours.<br />

Even with these observations removed, however, the mean delay is<br />

large relative to the predicted mean trip time of 8.15 hours and to<br />

the delay standard deviation. This signifies the importance of<br />

linehaul delays, even <strong>for</strong> unit-train movements which are supposed<br />

to . be unimpeded en route. However, while recognizing the importance<br />

of linehaul delays, no additional analysis of these will be provided<br />

here. Rather, economic analysis of the linehaul process function,<br />

146

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