Space-time convergence (also labeled as space/time compression) refers to the decline in travel time between similar locations. This implies that two locations can be reached in a lesser amount of time, which is usually the outcome of innovations in transport and telecommunications. Space-time convergence investigates the changing relationship between space and time, including 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 traded for 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 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 of -0.072 hours per year or -4.32 minutes per year. The value is negative because the time value is reduced (fewer hours traveled). If the value was positive, a space-time divergence would be observed.