cost saving rate ¼
A þ B cost À AB cost
A þ B cost
 100%
However, in terms of total number of vehicles used, individual scheduling
slightly outperforms collaboration. As depicted in Fig. 3.6, among the 60 testing
instances, the percentage that horizontal collaboration uses less vehicles is only 5%.
In most of the cases, individual scheduling needs less or equal number of vehicles
than horizontal collaboration. However, in around half of the instances, both scenarios ask for the same number of vehicle, and the maximal difference on the number
of vehicle used is 2 with percentage 13.33%.
Table 3.8 Case study results, for 60 customers
Instance A cost A nVeh B cost B nVeh A+B cost A+B nVeh AB cost AB nVeh
60_1
1916
11
1951
10
3867
21
2557
23
60_2
1663
10
1882
10
3545
20
2465
22
60_3
1811
11
1896
11
3707
22
2537
24
60_4
1779
11
1813
11
3592
22
2626
22
60_5
1672
11
1965
9
3637
20
2456
22
60_6
1812
11
1870
10
3682
21
2402
23
60_7
1954
11
1925
11
3879
22
2738
22
60_8
1837
10
1768
11
3605
21
2611
22
60_9
2008
12
2418
11
4426
23
2978
24
60_10
2056
11
1889
10
3945
21
2937
23
Fig. 3.6 The statistics on
the difference of vehicle
need on both scenarios
50
Sh. Sharif Azadeh et al.