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more rescheduling because crew P is only available at 6:30, which does not match any of the available duty. In this case, we need to find the crew that has the latest start work
1, which in this example is crew T 6:20. Therefore, crew T is chosen to take over duty 16. The second round reassignment is needed to reassign duty no. 20, which was
originally assigned to crew T. Duty no. 20’s start work time is 06:20. Whoever has a sign-on before or at 06:15 is eligible to take over duty 20. Table 4.3b shows the results
of second round rescheduling. The results show that crew X is the most suitable to take duty no. 20 because no more rescheduling is needed and there is zero waiting time for
late-crew. The overall results from this example show that crew P takes duty no. 24, crew T takes duty no. 16 and crew X takes duty no. 20.
Table 4.3a: First Round Rescheduling: 30 Minutes LFSO
Crew ID Duty No Sign-On Start
Work 1 New Start
Time Need More
Rescheduling Waiting Time for
Late-Crew
Q 17
05:56:00 06:11:00
06:10:00 Y NA
R 18
05:59:00 06:14:00
06:10:00 Y NA
S 19
06:00:00 06:15:00
06:10:00 Y NA
T 20
06:05:00 06:20:00
06:10:00 Y
NA
Table 4.3b: Second Round Rescheduling: Reassign Duty No. 20
Crew ID Duty No Sign-On Start
Work 1 New Start
Time Need More
Rescheduling Waiting Time for
Late-Crew
U 21
06:09:00 06:24:00
06:20:00 Y NA
V 22
06:10:00 06:25:00
06:20:00 Y NA
W 23
06:13:00 06:28:00
06:20:00 Y NA
X 24
06:15:00 06:30:00
06:20:00 N
00:00:00
4.2.4 LFR, LFSW and DFSW
The events of LFR, LFSW and DFSW are different in terms of the effect to crew schedules, and the time frame. However, from a rescheduling point of view the concern
is same, which is to reschedule the second work. When any of these events happen, the late-crew may or may not have enough time for relief. If the relief time is more than 45
minutes, and it can absorb the lateness, there is no need for rescheduling. However, if the relief time after taking consideration of the lateness time is not enough to absorb
the lateness, then rescheduling is needed. This is to ensure that the late-crew has enough relief time at least 45 minutes. The available crews for rescheduling are those that
have spent 45 minutes of their relief time and their end relief time should be later than
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that of the late-crew. If more than one crew is available, then the crew that has end relief time that is the same or close to the actual end relief time of the late-crew will be
chosen. In the case of more rescheduling being needed to find matches, then in the first round the late-crew’s duty will be assigned to an available crew that has the latest end
relief time of hisher original duty. This is because the later the finishing relief time is of the original duty, the closer it is to the actual finishing relief time of the late-crew.
This will result in less rescheduling and fewer crews will be affected by the changes. Thereafter, rescheduling will continue until the system finds a new duty for the late-
crew. These rules can be understood through the examples below. For example, crew P is assigned duty No.16. Crew P is supposed to finish work 1 at
11:10 but for some reason the crew is 15 minutes late. The late-crew informs the supervisor at the garage that heshe will finish at 11:25. The effects to the schedule after
taking account of 5 minutes to start relief, and relief time, should be at least 45 minutes. Crew P is due to finish his relief at 12:15 and is only available for hisher second work
at 12:20 as shown in Table 4.4.
Table 4.4: Effect of 15 Minutes LFR to Crew P
Finish Work 1
Start Relief
Finish Relief
Start Work 2
Real Time 11:25:00
11:30:00 12:15:00 12:20:00
Scheduled Time 11:10:00 11:15:00 12:05:00
12:10:00 Difference
00:15:00 00:15:00 00:10:00
00:10:00
Table 4.5a: First Round Rescheduling of 15 Minutes LFR of Duty 16
Crew ID Duty No Start
Relief Ready
Time Finish
Relief New Finish
Relief Need More
Reassignment Waiting Time for
Late-Crew
Z 26
11:19:00 12:04:00
12:11:00 12:05:00 Y
NA
Table 4.5b: Second Round Rescheduling of 15 Minutes LFR of Duty 16
Crew ID Duty No Start
Relief Ready
Time Finish
Relief New Finish
Relief Need More
Reassignment Waiting Time for
Late-Crew
S 19
11:27:00 12:12:00
12:17:00 12:11:00 N
00:02:00
In this situation, we must find another crew to take hisher second work. Based on the rules mentioned above, Table 4.5a and 4.5b show the outcome of the rescheduling.
The results show that two rounds of rescheduling are needed. In the first round, only
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crew Z is available to take the second work of crew P. In the second round, one crew is available - crew S. The overall results from this example shows that crew P will take
duty no.19, crew S will take duty no. 26 and crew Z will take duty no.16.
4.2.5 UNV
