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 evolving relationship between space and time, including the impacts of transportation improvements on that relationship. It is closely related to the concept of speed, which indicates how much space can be traded for a given 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 figure above illustrates space-time convergence between locations A and B. In 1950, it took 6.2 hours to travel between A and B. By 2000, the travel time had been reduced to 2.6 hours. Consequently, STC was -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 were positive, a space-time divergence would be observed, implying that it takes longer than before to connect the two locations.