The checkpoints, targeting busy entry points like Penn Station, are more of an awareness campaign than a blockade, intended to preserve the city's progress reducing its COVID-19 infection rate and forestall a second wave as the coronavirus ravages other states.

Authorities said this week a fifth of all new coronavirus cases in New York City have been from travelers entering the city from other states.

The random checks are similar to an effort already in place at airports and includes offers of free food delivery and in some cases even hotel stays for people who must quarantine.

Teams began stopping travelers arriving in the city by train Thursday, requiring they complete a state Department of Health traveler form and warning they could face fines as high as $10,000 for failing to quarantine.

The checkpoints don't involve the police, but the city's Sheriff's Office, which enforces civil law, said it would pull over motorists at random on city bridges.