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CHAPTER 5
Truck Turn Times
Terminal Versus Overall Turn Times
The key measure of drayage performance within the terminal is turn time, the time required
to complete an activity cycle. In the large picture, turn time refers to the entire round-trip move-
ment between port and customer or rail terminal. Those turn times are, however, customer spe-
cific and location specific, and influenced by distance, highway conditions, business practices,
drayage strategies, etc. There are two different turn times associated with marine terminal visits,
as follows:
· The terminal turn time recorded by the marine terminal is gate to gate, triggered by arrival
of the drayage driver at the entrance gate and ended when he leaves the exit gate. These
recorded turn times range from a minimum of about 10 minutes for a completed simple
transaction to as much as 8 hours. Marine terminals have no data on drayage activity out-
side those gates.
· The overall turn time experienced by drayage drivers, however, includes queuing time before
they reach the terminal gate itself. The additional time spent waiting outside the entrance gate
has been reported in various surveys to be as long as 2 hours. The study team observed waiting
times ranging from effectively zero when there was no queue, to 4 hours or more when termi-
nal operations were severely disrupted.
Turn Time Distributions
Gate-to-gate terminal turn times typically show, as expected, a skewed distribution (Fig-
ure 51). The first terminal shows a few unusually quick transactions of less than 30 minutes,
a large number of "normal" transactions of 3060 minutes, and a few much longer transac-
tions that reflect exceptions. The second, more heavily used terminal shows somewhat longer
turn times but the distribution has the same overall shape--skewed toward the longer turn times
by exceptions. The "normal" time varies with the complexity of the transaction and the type
of terminal.
Figure 52 compares a distribution of port-wide trucker turn times (includes queuing) with ter-
minal turn times (does not include queuing) from one of the terminals in the same port. Although
the comparison is not precise, the available data suggest that the trucker's turn times typically
include 2030 minutes of queuing time, shifting the distribution to the right.
The critical factor is the common shape of the distributions in Figure 51 and Figure 52. In
each case there are roughly 5% of the trips in the extended right-hand "tail" of the distribution
that experience much longer turn times and account for a disproportionate share of drayage
time, cost, and emissions. The system is effectively operating at "two sigma," with about 95%
39
