There are four major categories of friction of distance functions:
- No effects of distance (1). Economic activities on which distance has no effect are uncommon. However, the distance-cost function of telecommunication networks, and the virtual space of the Internet have such a cost structure. Telephone calls and data roaming charges can be included in this category as well as postal fees and public transit fares. All those activities generally have a fixed cost which is not related to distance, but often to a service zone. Once a new zone is entered (such as for international phone calls) a new cost structure applies.
- Linear effects of distance (2). Transport costs are increasing proportionally to distance. Fuel consumption can be included in this category since it directly affects the distance traveled. For simplicity, a step-wise approach is often used to establish transport rates by using administrative units as distance units.
- Non-linear effects of distance (3). Freight distribution costs are growing in a non-linear fashion with distance from the terminal or the distribution center, particularly because of empty back-hauls (a). Inversely, international air transportation costs are not usually higher than regional air transportation costs because long-haul planes have more capacity and fuel efficiency (b).
- Intermodal transport chain (4). A combination of linehaul and terminal costs where transshipment costs at terminals (e.g. ports and airports) increase the friction of distance as efforts must be spent at loading or unloading when passing from one mode to another.