Source: adapted from Janelle, D.G. (1968) "Central Place Development in a Time-space Framework", The Professional Geographer, Vol. 20, pp. 5-10. Data for 2000 and 2010 based on direct scheduled flights.
Regional Space / Time Convergence, (London - Edinburgh, New York - Boston)
The above graphs displays a process of space / time convergence between two city pairs, London and Edinburgh (located 520 km apart) and New York and Boston (located 310 km apart). Both city pairs went through a different space / time convergence process, which is indicative of time differences in the introduction of new transport infrastructure and services. With the development of stage-coach services in the 18th and early 19th centuries, travel times declined substantially. However, by the 19th century stage-coaches reached their optimal efficiency and could no longer provide time improvements. The development of rail networks initiated a new phase of space / time convergence and by the early 20th century travel times were significantly lower than previous decades. The development of highways and then air transportation systems from the mid 20th century reduced travel times to 100 minutes between London and Edinburgh and to 70 minutes between New York and Boston. By 2010, travel times scheduled flight times between New York and Boston remained unchanged mostly because of airport capacity issues. However, scheduled flight times between London and Edinburgh improved by 10 minutes, leaving a travel difference of only 10 minutes between both city pairs even if London-Edinburgh is 200 km further than New York - Boston. It is unlikely that these figures will change anytime soon. Contemporary space / time convergence dominantly takes place at a global level and are derived more from intermodal improvements than from modal speed improvements.