Picton ferry terminals are heavily congested after an influx of people who don't have tickets for crossing are trying to get on Interislander and Bluebridge Ferries.
It is causing significant delays in Picton, police said in a statement.
People around the country, including a large number of tertiary students, have been rushing to get home before the mandatory Covid-19 coronavirus self-isolation period starts at 11.59pm on Wednesday.
Police urge anyone who is not booked on a ferry crossing this morning to not turn up.
Police are currently providing traffic management support near the ferry terminals.
KiwiRail Group chief executive Greg Miller said in a statement he urges passengers to be "patient."
KiwiRail is working with police and other stakeholders to help people get home before the self-isolation period starts.