You may want to clarify the average amount spent to commute. There are lots of ways to calculate this - depreciation on vehicle, maintenance per mile, fuel, insurance, etc. For example, I calculate that my Volvo costs me ~$0.80/mile to drive (not including insurance - it's actually worse than my 1098 was, which ended up just less than $0.60/mile), my SV is somewhere around $0.20/mile (that includes a lot of crash repairs...), and my Brammo is somewhere around $0.04 a mile (not including insurance or any depreciation).
I ended up putting $1 if for both measures since the survey wouldn't take anything less than that. I assumed you only wanted fuel costs. My commute is 35 miles round trip, though.