Not many at all - little less than 9 (each way, but going to work was no problem at all) - my usual fall/winter commute. I think I killed the knees on one particular 1/2 mile stretch where I just had to stand and mash to keep the bike moving forward with the slipping on the tiny footprint hills. Looking back, I should have dismounted and walked it up. But having never walked it before, I was sure I could just power on through it. Mistake.