You don't think there's a chance that working 4 days instead of 5 reduces the physical toll to keep you going longer and working better? Wouldn't working 4 days a week reduce your stress, allow you to recover from all that heavy lifting you mentioned, and improve your physical and mental health on the long-run?
Besides, as I understand it, if your company still wants you to work 5 days, you would still have the option. This bill would require them to pay you overtime for that extra day.
Okay, now factor in car insurance and maintenance costs. I don't buy your statement "taking the car is 2-3 times cheaper".