In 1995/1996 Correos y Telégrafos, the public and main mail company from Spain, decided the construction of a new sortation centre for mail and parcels in Madrid. As a part of the project, Correos bought to MODELCO four WITNESS licenses, to train own staff and to done a simulation study of the material flow in the new sortation centre. The simulation tool should help Correos to get the right dimensions of some parts of the centre, like buffers and numbers of sortation machines.

Simulation model

Elements	Mail types Handling units Sortation and processing machines Transport vehicles Operators Conveyors Areas of the distribution centre Workflow
Inputs	Time distribution of the input flow (volume / hour) from the different sources (mail boxes, offices and big customers form different distances to the sortation centre)
Main parameters	Operating parameters of the machines, conveyors, internal transport vehicles Performances of the different manual operations Incidences in different elements Surface of the different areas Number of machines, transport vehicles and operators

The simulation model has been used for:

• Evaluation of the influence of the time distribution of the incoming mail depending on the source (distance from post office or mail box to the sortation centre). Incoming Mail distribution curve.
   
• Study of the number of machines and conveyor needed to guarantee the required service level (mail received and shipped in the same day)
   
• Calculation of the right dimensions for the manual sortation areas that should process the mails and parcels that can not be processed automatically (not enough capacity or non machine sortable mail)
   
• Evaluation of the right dimensions for buffers (receiving, conveyors, shipping) and receiving and shipping areas (no of unloading and loading docks)
   
• Calculation of the number of internal transport vehicles needed (lift trucks, etc) and personnel required to operate the sortation machines (input and output and video indexing)
   
• Study of some typical incidences (for example, delay in incoming mail). Identification of bottle necks and quantification of critical areas
• Study of the empty totes and trolleys material flows and buffer requirements.