This article highlights an application in the area of decision support for planning transports in a railway company utilising
constraint logic programming and a flexible design which has been successfully tested on real world data.
We discuss the problem formulation for the co-ordination of distinct sub-problems, the allocation of track resources to transports,
the allocation of vehicles to transports, and the allocation of personnel to perform the transportation tasks in a railway
company and the development of a heterogeneous constraint model which is usable also for other production planning problems.
Using constraints as the key technology, we discuss approaches to find interfacing principles to combine several solvers.