The demand among Delhi’s homeless for safe, state-run spaces has long outweighed the supply. That leaves thousands of homeless men, women, and children sleep out in the open: on pavements that divide busy roads, or under bridges and stationary cars. In the summer, heat or mosquito-borne diseases claim the lives; in the winter, it’s the freezing cold.

Every few months or so, news of a car running over some pavement-sleepers make the headlines. But such incidents barely register on the radar of the city’s more privileged residents.

From 2004 to 2015, more than 33,000 homeless have died on the streets of the capital for many of the reasons mentioned above, according to government estimates. Those who survived have remained invisible. A new documentary called Cities of Sleep explores their world, uncovering how terribly fraught such a basic human need has become for the people at the base of the India’s socioeconomic hierarchy.

“The idea was to look at sleep through a social and political lens,” Delhi-based filmmaker Shaunak Sen tells CityLab via Facebook. “Just a good night’s sleep is a matter of life and death for some people.”