More than 750 cars are on display at Detroit’s annual auto show, which opened for media previews Monday. It is one of the largest auto shows in the country – setting up the exhibition space takes months, says Rod Alberts, executive director of the North American International Auto Show, which is the Detroit show’s official name. Lighting installation alone took two weeks.

Yet for all that work, no cars are available for sale. So what’s the point?

A primary goal, Alberts says, is to help auto manufacturers get media attention for their new cars. David Cole, a former professor of auto engineering and chairman of AutoHarvest.org, says manufacturers also use auto shows to see what upcoming offerings resonate with the public.