COVID-19　continues　to　threaten　the　world.　Relaxing　local　travel　behaviours　on　preventing　the　spread　of　COVID-19,　may　increase　the　infection　risk　in　subsequent　waves　of　SARS-CoV-2　transmission.　In　this　study,　we　analysed　changes　in　the　travel　behaviour　of　different　population　groups　(adult,　child,　student,　elderly)　during　four　pandemic　waves　in　Hong　Kong　before　January　2021,　by　4-billion　second-by-second　smartcard　records　of　subway.　A　significant　continuous　relaxation　in　human　travel　behaviour　was　observed　during　the　four　waves　of　SARS-CoV-2　transmission.　Residents　sharply　reduced　their　local　travel　by　51.9%,　50.1%,　27.6%,　and　20.5%　from　the　first　to　fourth　pandemic　waves,　respectively.　The　population　flow　in　residential　areas,　workplaces,　schools,　shopping　areas,　amusement　areas　and　border　areas,　decreased　on　average　by　30.3%,　33.5%,　41.9%,　58.1%,　85.4%　and　99.6%,　respectively,　during　the　pandemic　weeks.　We　also　found　that　many　other　cities　around　the　world　experienced　a　similar　relaxation　trend　in　local　travel　behaviour,　by　comparing　traffic　congestion　data　during　the　pandemic　with　data　from　the　same　period　in　2019.　The　quantitative　pandemic　fatigue　in　local　travel　behaviour　could　help　governments　partially　predicting　personal　protective　behaviours,　and　thus　to　suggest　more　accurate　interventions　during　subsequent　waves,　especially　for　highly　infectious　virus　variants　such　as　Omicron.　©　2023　The　Author(s)