It doesn't have to totally replace cars. The ideal is to drop down from a 2 car household to a 1 car household and only use it for bigger errands and trips, or you drop down to a 0 car household and use the money you save on car payments, gas, and insurance to occasionally rent or carshare. The best is for biking/walking/transit to replace daily trips to/from places like work, dinner, downtown, the movies, the park, etc.