Longman Dictionary of Contemporary English
commuter belt
noun
EXAMPLES FROM CORPUS
▪ But of course they did not circulate beyond the commuter belt, so they failed to qualify as nationals on that ground.
▪ Then another train towards the Kent commuter belt, and Dartford.
Wiktionary
commuter belt
n. A zone surrounding a metropolitan area or city from which commuters travel to the area or city to work.
Usage examples of "commuter belt".
They were out of the commuter belt now and the carriage was half empty and filled with a grim silence.