As urban populations grow and analysts continue to predict dwindling car ownership, alternatives have sprung up and automakers are gradually getting in on that sweet car-sharing action. Currently active in 17 North American cities, General Motors' hourly ride-sharing unit Maven has been building slowly.

GM is now expanding Maven to include long-term rentals which, come to think of it, sounds identical to what it was doing with its Book by Cadillac premium subscription service. While the Caddy offering is intended to be a monthly subscription serving as an alternative to normal vehicle ownership, nothing is really stopping customers from using "Maven Reserve" in a similar manner.

Also similar is the pricing. While the special Maven Reserve vehicles don't yet encompass all GM's fleet, a Chevrolet Tahoe runs $1,500 for 28 days, which is identical to the subscription fee for Cadillac Book, which also includes curbside car delivery and mid-month vehicle swapping.

In essence, GM is allowing you to have simultaneous access to a CTS-V and Escalade or a Tahoe for the same amount of money.

To compare, the Tahoe can be leased in a traditional manner for $299/month and found for similar, occasionally lower, monthly rates through traditional rental agencies - provided you are less picky and they aren't gouging for larger vehicles, which they may. Drivers can also use Maven's normal on-demand service and get that same vehicle for roughly $14 an hour or a slightly discounted daily rate.

At the moment, the only other long-term option is an extended-range Chevy Volt for $1,100. GM explained the limited offerings are due to the program's initial California location and customer preference. When monthly rentals eventually roll out to other parts of the country, expect more options.

The case to be made for Maven Reserve over Zipcar or an airport rental is that General Motors provides SiriusXM satellite radio, 4G LTE WiFi. insurance, a $100 gas voucher, and a parking space for when you aren't driving. However, the usefulness of that space will be largely dependent upon how close it is to your home base. While any open slab of concrete is worth its weight in gold in a densely populated city, its of no help to you if you can't easily access it.

Maven Reserve is currently only available in Los Angeles and San Francisco while Book by Cadillac exists in the New York Metropolitan area. However, GM says it anticipates expanding both services to other cities soon.