Cities most dependent on a diverse mix of walking, cycling, and public transport tend to be compact in form and become multi-nucleated as they expand in size, with heterogeneous land use at a small scale, mixing residential, retail, and often some production functions. Where public transport is predominant over non-motorized modes, average trip lengths and transport costs are higher. In contrast, cities highly dependent on the automobile generally sprawl at low densities, with long average trip lengths, spatial separation of different land uses from each other, and little diversity of mode choices. The trip length distribution of a city, set by the current land use and general costs of transport, determines to a large extent the opportunity for interchangability of motorized and non-motorized trips. For person trips with small loads, walking is typically the most efficient mode for short trips of up to one kilometer.
Cycling is usually the most efficient mode for trips of half a kilometer to several kilometers.
The maximum efficient range of walking and cycling for individuals depends on income. Cost sensitive low income people commonly prefer to walk or cycle much longer distances to avoid the expense of public transport fares. Especially as cities grow larger, the need to make longer trips usually grows. Since walking and cycling are too slow to be efficient for longer trips, motorized transport become the optimal mode choice. If demand is very high, rail or dedicated busway services are usually most efficient, but must often compete with less efficient automobiles and motorcycles.