These problems have been tackled using a CP approach described in [1] and by the Local search method, GENET described in [2]. The adapted GENET program has found solutions with the same number of shifts as TRACS II for several of the problems. The systematic CP approach has done this for all the problems except c2, r5 and r5a. These are slightly larger than the rest, c2 has 14771 potential shifts, 205 pieces of work and 29 shifts in the TRACS II solution and r5a is of similar size. However, these have been easily solved by TRACS II which can solve problems an order of magnitude larger (it can solve problems where the numbers of shifts, pieces of work and shifts in the solution are ten times bigger).

[1] S. D. Curtis, B. M. Smith, and A. Wren.
Forming bus driver scheduling using constraint programming.
In Practical Application of Constraint Technologies and Logic Programming PACLP99, pages 239-254. The Practical Application Company Ltd, 1999.
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[2] S. D. Curtis, B. M. Smith, and A. Wren.
Constructing Driver Schedules using Iterative Repair.
Submitted to PACLP00, The Practical Application Company Ltd, 2000.
Tech. report version will be available soon at this link.