Fuel is the number most people think about. It is rarely the biggest one.
The full picture on a 28 km commute
Twenty-eight kilometres each way, twenty-two working days a month, is roughly 1,230 km. At 14 km per litre and current pump prices, that is the fuel line. Then add tolls, parking, servicing every 10,000 km, tyres, and the depreciation that mileage causes.
What sharing changes
Three passengers contributing a fair share of that trip cost does not make a driver money — that is not what carpooling is for, and on Safrly contributions are capped at cost sharing. What it does is move the majority of a fixed monthly expense off one person.
The part that does not show up in a spreadsheet
Three fewer cars on the same route, three fewer parking spaces used, and a commute with company. People keep carpooling for the last one more often than the first.