In the early 21st century, predictions were made that due to economic migration indicators, the urban areas of Glasgow and Edinburgh, whose centres are approximately 41 miles (66 km) apart, could merge to create a megalopolis over the coming decades.
[5] encompassing towns such as Paisley, Cambuslang, Hamilton, Stirling, Falkirk, Cumbernauld, Livingston and Bathgate.
[6] The larger Central Belt is a trapezoid, not precisely defined, but essentially encompassing the generally low-lying areas from Helensburgh to Montrose (the Highland Boundary Fault) and from Girvan to Dunbar (the Southern Uplands Fault).
Including rural parts of the council areas involved,[c] the total population was around 4.28 million in 2018.
[6] There are several terms in common usage in a Scottish context with a similar meaning to "Central Belt".