I rounded up my daily commute by car to my office--one way--to 25 miles. So that makes milage for the day 50 miles. For the week, five days of driving, the total is 250 miles.
1000 miles per month if I drive to work five days a week.
If I were to only ride round-trip 20 miles, five days a week, which would be my shortest easiest commute distance by bicycle, for one month--that would be 400 miles on the bike.
So by putting out very little effort (in terms of the difficulty and short distance of that 10 mile commute) I am significantly reducing the miles I drive by car.
Wow--600 miles compared to 1000 miles.
Not that I will ever be able to accomplish this, but say I rode my 30 mile round trip commute route every day for one month. That would be 600 miles on the bike--still 400 miles by car.
The Pros--Saving the Planet, getting buff, feeling fit and ready for brevets, and energy for all my girlfriends, mes amis!
The Cons--Up my chance of being run over by a car.
Today I did drive in, but I got it together and went and swam laps at the pool for my lunch hour.