Auto factories are pushing workers and plants in order to meet the demand fr new vehicles. Plants are adding third shifts, increasing the work week and overtime, as well reducing the shutdown at some plants. Ford says that many of their plant at working at maximum capacity. Demand for vehicles is up over last year. Car makers sized down after the recession, and do not want to have too many factories, instead pushing the ones they do have to produce more.
See "Autoworkers pushed to limit as many plants max out", Chris Woodyard, Detroit Free Press, May 22, 2012