If you compare the cost of owning a car to taking public transportation, it doesn't take much time to see the difference in cost.  However, if you are thinking of getting a moped or scooter, the cost of purchasing and operating is much lower than a car, so the cost consideration might be closer.  You may have to look at other factors when deciding between buying a scooter and taking public transportation.   

Trans or buses can cost about $50 to $100 per month, depending on where you live, and train frequency can be as often as one every five minutes, or one every hour.  During rush hour you may have to stand in the train as well.  Furthermore, trains and buses go to specific places, meaning you still may have to walk a considerable distance, which can be a drawback if you will be walking around at night.

Mopeds, on the other hand, can be an affordable option as well.  After an initial purchase price of $3,000 or so, you can expect to get a lot of great gas mileage on it.  Cheap mopeds can go for even less than $1,000 if you buy a used model and get a good deal.  The benefits of mopeds are that you have the freedom to travel whenever you choose, rather than following the schedule of the bus or train, which can get infrequent on weekends and holidays. 

You will also save time in traffic jams as you can pass cars that are slow or stuck.  If you have a family, then this might not make sense, but you can take another passenger no problem, as most used Vespas can take 250 pounds of weight on them and more.  So if you want an affordable alternative to driving, consider public transportation and a more fuel-efficient vehicle like a scooter.  Either way, you will be spending less and be more environmental friendly.