When Hollywood stops distributing movies on 35mm film at the end of this year, that leaves the few drive-in theatres around the country in the lurch.

All theatres, indoor and outdoor, will soon be required to use digital projectors. But while indoor screens got financial assitance to make the transition, outdoor theatres were left struggling to figure out how to afford the more than $70,000 it takes to switch.

Already, the number of drive-ins have plummeted from their height of more than 4,000 in the late 1950s, to less than 400 today. And so theatres that closed for the winter may stay closed, dimming more screens across the country.

Kipp Sherer from Drive-Ins.com explains how some theatres are managing to hold on, and where the audience is still coming in droves to sustain these classic venues.