From Longman Dictionary of Contemporary Englishcommuter beltcomˈmuter ˌbelt noun [countable] British English SGan area around a large city, from which many people travel to work every day
Examples from the Corpus
commuter belt• Then another train towards the Kent commuter belt, and Dartford.• But of course they did not circulate beyond the commuter belt, so they failed to qualify as nationals on that ground. 