From Longman Dictionary of Contemporary Englishin relaysin relaysCONTINUOUSif people do something in relays, several small groups of them do it, one group after another, so that the activity is continuous → relay
Examples from the Corpus
in relays• The unvarying conditions also promote long breeding seasons with breeding in relays.• The plan was to go in relays and not to leave the Jonquil unattended, but there was a muddle.• The road along which the divine bearers marched in relays had neither beginning nor end. 