I remember when both the suburban trains and the BVG (underground, tram and bus service) were on strike here in Berlin. A lot of people here don't even have cars. Thankfully, this lasted only for a few days, the period where one of the two was on strike was much longer, though (especially the suburban trains).
I ended up staying home from university when that happened. I got lucky because on the days I had to work, they weren't on strike.