Oh yes! Good idea, Frus! You'd be combining your commute AND your aerobic exercise - you'd get a lot more time to yourself and it'd be cheaper in the long run.
I've never heard of anyone getting mugged while they were actually on a bike - you would just need to take sensible precautions like wearing light reflective clothing, carrying a personal alarm and keeping your wallet/purse tucked inside your clothes.
I know its not the same thing but perhaps you could do some kind of time calculation based on your speed on an exercise bike.
You could work up to 16 miles! Think how fit you'd be doing that every day! 
