Space / Time Convergence
Space / time convergence (often labeled as space / time compression) refers to the decline in travel time between locations, which is the outcome of innovations in transport and telecommunications. It investigates the changing relationship between space and time, and notably the impacts of transportation improvements on such a relationship. It is closely related to the concept of speed, which indicates how much space can be traveled over a specific amount of time. To measure space / time convergence (STC), travel time information is required for at least two locations and two time periods. Variation in travel time (ΔTT) is simply divided by the time period (ΔT) over which the process took place; the slope of the curve.
The above figure provides an example of space / time convergence between two locations, A and B. In 1950, it took 6.2 hours to travel between A and B. By 2000, this travel time was reduced to 2.6 hours. Consequently, STC was for that period -0.072 hours per year, or -4.32 minutes per year. The value is negative because the time value is being reduced (less hours travelled); if the value was positive, a space / time divergence would be observed.