Black trash bags are a common fix to temporarily cover a broken car window - but they don't work! Obviously, you can't see through it, you can't use it on the road, and - in this application -you can expect rain to get in the car. Big Tape is a better solution until you can get your window fixed!
Did you know over 1 million vehicle windows are smashed every year in robberies? San Francisco alone last year had over 25,000 windows broken and thieves broke in to grab stuff out of cars.