To those who say that self-driving cars have nothing to do with Google's core business selling ads, listen up: Google was just awarded a patent for an ad-powered taxi service.

The patent, which was first spotted by TechCrunch, would allow advertisers to offer potential customers a free ride to their place of business. This would solve one of the biggest problems for brick-and-mortar retailers: getting customers to their location. The system would offer free or discounted transportation based on an algorithm-powered decision-making process involving the user's current location, the cost of transportation, and the potential profit from a completed sale. The concept is basically a "free ride coupon" and mentioned transportation modes like taxis, trains, buses, or even autonomous vehicles.

The ads would be displayed either via cell phone (which could detect the user's current location) or from a stationary kiosk in a public area. The ads would, of course, be highly targeted. In the smartphone example, Google would identify the user by their phone, and for the public kiosk example, a user would be asked to identify themselves ("Sign in to your Google+ account!"). The system would track how often you use the discounted transportation to make a purchase, and if you bum too many free rides without buying something, advertisers may not offer you a ride next time. The patent also mentions that users could offer up information about themselves, like who else is with them, to get recommendations from advertisers and browse the discounted transportation catalog. For instance, two adults may want to go to dinner, while an adult and child might want to go to a family friendly establishment. Advertisers would bid against each other, just like they do for Google ads, based on your purchase history and other factors in your profile.

It's unclear if Google plans to implement something like this soon or if the idea is part of a post-driverless-car utopia. For what it's worth, the patent was cooked up by members of Google's driverless car division. An advertiser paying for a bus, train, or taxi might be a little too expensive today, but imagine a self-driving electric vehicle, where driving around doesn't burn gas or involve paying a taxi driver, and suddenly transportation becomes a lot cheaper. Perhaps it would eventually be cheap enough that your local business would pay for your taxi fare, as long as you promise to buy something.