Cost
The comparison most calculators fudge is the car column. Keeping the car and riding a scooter saves fuel; replacing the car saves everything. Both answers are here.
Ridable weeks is the honest input most comparisons skip. Ice, heavy rain and darkness push a lot of riders back into a car for part of the year, and those miles get priced back into the scooter column below.
Marginal mode adds 10 cents a mile on top of fuel for tyres, brakes and oil. Insurance, depreciation and registration are excluded, because you pay those whether or not you ride.
At these numbers the scooter pays for itself against driving in about 37 months. Nothing here prices your time, and a scooter is often the fastest of the four on a congested two to five mile trip.
Your inputs, mostly. The one figure baked in is ten cents a mile of car wear on top of fuel in marginal mode, covering tyres, brakes and oil. For full-ownership mode, the IRS standard mileage rate is a reasonable starting number if you have nothing better.
Time, weather, parking hassle and the risk profile of each option. On a congested two to five mile trip a scooter is often the fastest of the four, and none of that shows up in a dollar total.