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, postal fees, and public transit fares can be included in this category. All those activities generally have a fixed cost unrelated to distance but often to a service zone. A new cost structure applies once a new zone is entered (such as for international phone calls).
- 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 non-linearly 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.