Line blocking regards the vehicle journey sections of the model for planning, the generated blocks thus successively traverse vehicle journey sections. For planning, either all or all active vehicle journey sections, or - orthogonally thereto - either all sections or only those not yet being bound in the target block version can be regarded (Using Visum: Parameters of the line blocking procedure). Prior to the graph construction, the problem is broken down into subproblems, so-called partitions, which are to be solved separately. A partition consists of all vehicle journey sections to which the same vehicle combination has been assigned. The decomposition into these subproblems is possible, because a block is always run by exactly one vehicle combination and there is therefore no vehicle change within the block. Also the vehicle journey sections which do not have a vehicle combination, together form a partition. For each partition, all further procedure steps are carried out separately. Thus, a separate graph is constructed and solved for each partition and each result will be decomposed into blocks.
As an option, line blocking can be partitioned further according to operator, transport system, and line (Using Visum: Parameters of the line blocking procedure). If for example the same operator is required for the next vehicle journey, operators are partitioned additionally. In this case each partial problem and thus each resulting block only contains vehicle journey sections of a vehicle combination and of an operator. Operator changes can therefore not be made within a block. Within the procedure, a separate graph is set up for each combination of vehicle combination and operator, and the other procedural steps are carried out for each of these graphs. The Illustration 193 shows an example of partitioning. These are vehicle journey sections run by three vehicle combinations: articulated bus, standard bus, and tram. The articulated bus vehicle journey sections are run by operator 1 and 2, whereas the tram vehicle journey sections are run by operator 1 only. If line blocking is additionally partitioned according to operators, five graphs will be built, for which the flow problem has to be solved separately and the decomposition into blocks needs to be carried out separately.
Illustration 193: Example for partitioning according to vehicle combination and operator
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Note: Capacity restrictions in depots can only be considered if the graph is not partitioned further than by vehicle combination, i.e., if none of the options Same operator for next vehicle journey, Same transport system for next vehicle journey or Same line for next vehicle journey have been selected. The reason for this being, that the capacities in depots are each defined per vehicle combination. If a more detailed partitioning is carried out for example according to operators, the procedure does not have the possibility of distributing the capacity, even further to the level Vehicle combination x Operator. |
