Source: Adapted from P. Hugill (1995), World Trade since 1431, Baltimore: The Johns Hopkins University Press, p. 213.
- Walking. Assuming a willingness to commute for one hour, a pedestrian walking at 5 km per hour could cross about 5 km. The space / time relationship of such a commute would be a circle of roughly 10 km in diameter. This helps explain why prior to motorization, cities were compact since most of the mobility took place by walking. The majority of cities present prior to the industrial revolution have kept a high density urban core.
- Streetcar. A streetcar, like those operating in the first half of the 20th century, could travel around 15 km per hour along fixed lines. In this case, the space / time relationship would be to reflect the time spent walking to the streetcar line that has to be deducted to the total travel time. Therefore, someone being 15 km away from the city center would need to live next to the streetcar line to fall within the range of one hour maximum commuting time.
- Cycling. The bicycle became a mode of mass transportation in the late 19th and early 20th centuries. With approximately the same speed of a streetcar, but with no fixed line limitations, the space / time relationship of commuting by bicycle would be a circle of 15 km in diameter. The influence of the bicycle on urban form was tenuous and short lived. Still, many cities around the world have implemented bicycle friendly infrastructure such as bike paths and parking areas.
- Driving (no freeways). With a driving speed of about 30 km per hour (taking into account stops, congestion and parking), an automobile creates a spherical space / time relationship of about 30 km in diameter. This permitted the formation of the first car-oriented suburbs, many of which serviced by buses.
- Driving (with freeways). Along a freeway, a fixed infrastructure, the driving speed is doubled to 60 km per hour along the main freeway axis. The space / time relationship is therefore star shaped with 60 km of diameter along its axis. However, under such circumstances a city can become multi-nodal.