The simplified delivery service model: The SDS model involves the geographical division of the marketing territory into sub-areas. Each sub-area is identified by an alphanumeric code (e.g. D2). The alpha part of the code indicates a main route from the depot into a particular sales area and the numeric component breaks that sales area into suitably sized sub-areas. These sub-areas are often but not always delineated by physical boundaries such as rivers, valleys, mountains, etc. Consideration is also given to the number of customers in each area categorisation used for the purpose of the simplified delivery service.