A simple distance radius is no longer suitable in determining the trade area of a shopping centre, a retail outlet, a fast food outlet, a petrol station or even a bank. Almost all service based economic activities need to identify their trade area or catchment to determine their most potential location. Drive Times, Drive Distances, Customer Locations and a lot of other factors determine the trade area, trade zone or catchment of a service outlet. Definite population sizes and income levels within an area also determine the catchment area of the shopping mall, hypermarkets and supermarkets, coffee house and fast food outlets

The above two maps show how the simple circle radius can mislead a retailer to indicate a larger area than that of a DRIVE -TIME based catchment. By conducting an exit survey and and geo-coding the location of the customer, the actual catchment can be define as seen in the sample map below.

The location of the customers of the retail centre  is mapped and then overlaid onto a drive time map derived from a GIS system using pre-determined speed limits for the road network within this catchment. From here it is clear where the PRIMARY Catchment is. This would then determine who the shopping centre retailers should cater for more. The road network also plays a major role in determining not only the extent of the secondary catchment but also the primary catchment.