Dead End Drive In (1986)

When Crabs takes Carmen to the drive in, and tells the owner he is unemployed so he can get a discount on tickets.  During the night, two of his tires are stolen.  Unable to leave because the drive in is miles from town, they discover there is no public transportation that stops there, and it's illegal to walk on the road.

The two are forced to stay there, but the good news is the government will provide vouchers for food.  There are groups of people living in cars, tents, and makeshift shacks.  Most of them are okay living there as they were already unemployed. But Crabs is not happy at being detained and wants to leave.  No one will let him, so he plots his escape.

It's social commentary disguised as horror film. The drive ins are essentially prisons where they lock up the useless, outcasts, and criminal  members of society. Those who don't contribute to society are sent there and the discount for being unemployed provides a new source of prisoners..  The majority of them are fine with roaming the drive in during the day, getting vouchers for food, and watching movies at night.

It's Australian and it's post apocalyptic.