Parking at airports seems a terrible waste -- expensive parking and your car sits doing nothing. I first started thinking about the various Car Share companies (City CarShare, ZipCar, FlexCar -- effectively membership based hourly car rentals which include gas/insurance and need no human staff) and why one can't use them from the airport. Of course, airports are full of rental car companies, which is a competitive problem, and parking space there is at a premium.

Right now the CarShare services tend to require round-trip rentals, but for airports the right idea would be one-way rentals -- one member drives the car to the airport, and ideally very shortly another member drives the car out of the airport. In an ideal situation, coordinated by cell phone, the 2nd member is waiting at the curb, and you would just hand off the car once it confirms their membership for you. (Members use a code or carry a key fob.) Since you would know in advance before you entered the airport whether somebody is ready, you would know whether to go to short term parking or the curb -- or a planned long-term parking lot with a bit more advance notice so you allocate the extra time for that.

Of course the 2nd member might not want to go to the location you got the car from, which creates the one-way rental problem that carshares seem to need to avoid. Perhaps better balancing algorithms could work, or at worst case, the car might have to wait until somebody from your local depot wants to go there. That's wasteful, though. However, I think this could be made to work as long as the member base is big enough that some member is going in and out of the airport.

I started thinking about something grander though, namely being willing to rent your own private car out to bonded members of a true car sharing service. This is tougher to do but easier to make efficient. The hard part is bonding reliability on the part of all concerned.

Read on for more thinking on it...

It would begin with Alice, a member of the service ("Flying Cars") driving her car to the airport. She calls a special number on her speed dial when she's about 5 minutes out. It catches her caller-ID and tells her to park in the long-term lot, the short-term lot or to meet somebody already waiting at her terminal or one before it, and tells her a code-word for identifcation. In advance, she put personal gear she keeps in the car in a special locker that goes compactly in the trunk, and is locked to the trunk with a special lock.

Later, Bob flys into the airport, and needs to get somewhere not too far from Alice's home. He arranged it on the web or phone before he got on the plane, and when he lands he calls on his cell phone for a final confirmation, and the code that unlocks Alice's car. He drives to his own destination, and unloads his bags. Then what he does depends on what Alice wants done with the car. He might drive it back to Alice's house, which is not too far away, or is easy to reach by transit, taxi or road. Most commonly, he has somebody else with him now at the house who can drive a 2nd car on the short hop to Alice's. At Alice's, there is of course a parking spot available. If it's a driveway spot that's best. Alice may have to choose between letting Bob into her garage (with the garage door opener probably in the car) or leaving the car on the street or driveway for a few days. In this case the car is probably done, and is waiting for Alice when she returns by other means (most probably the car of another person who lives not too far away.)

Alice may also have indicated her car can be used for other rental trips. These could be trips to the airport, or even ordinary carshare rentals depending on her taste. For the drive home from the airport, and any other such trips, Alice earned a rental fee per mile. In this case the car can stay at Bob's if Bob has a parking space for it (which is convenient for Bob) or be driven to Alice's space, or even any other close space provided by a member -- in this case for a fee. Alice would not charge a parking fee, and nor would Bob, for the convenience they gain.

Ideally for Alice, somebody else from the area wants to go to the airport a short time before her return trip. That person, Carl is told where to pick up the car (probably not in Alice's garage though this is not impossible) and has a friend, taxi or transit take him on the short trip with luggage. Carl drives to the airport -- ideally meeting Alice at the curb, but probably putting the car in a parking lot. When Alice flys in, her car is waiting in a parking lot, but with only a few hours parking charge on it. (The Flying Cars service might arrange to include the parking costs in the price of service and average it out.) Alice has probably made money on the arrangement, rather than paying $50 to park her car at the airport.

If the Flying Cars service has arrangements with parking lots, they could take Alice's locker from the trunk, store it securely and return it before Alice gets the car again.

If you get to a critical mass, where members from neighbourhoods are regularly going to and from the airport, the cars would barely have to park there at all, and this would work really well.

There are some big issues though:

• Gas must be paid for. Alice should fill the car before any period she's renting it out. The algorithms would arrange so it is not rented for enough miles to risk making it low on gas. Or, if it becomes low on gas, a filling system like that at the carshare companies could be used.
• Alice has to keep her car clean and neat, and her stuff in the locker when renting it out. If she doesn't, she'll get comment scores from renters and nobody may want to rent her car.
• Alice must keep the car in top mechanical shape. It probably has to be a late-model car to be in the system, no more than 3 years old. In addition, there may need to be a requirement for inspection by a contracted mechanic (hopefully Alice's regular mechanic) on a regular period. To rent out, there must have been an inspection within some recent time period.
• The members must be very trustworthy. Clearly joining will require some bonding, verification of ID, probably more than Hertz wants.
• A clean driving record will be a must. While Hertz can evaluate the risk you smash up a rental car, that's just money. If a renter smashes up your own car, it can be more than a financial cost to people. Plus there is the risk they will want to sue you, claiming mechanical failure.
• Somehow it must all be insured. This may have to just come out of membership fees. It may be possible that some member's insurance on credit cards or existing policies can handle it, but that's for renting. The car owners won't want their own insurance records hurt by having to make claims from renter accidents.
• In particular, there will have to be workable policies on wear-and-tear damage -- a scratch here, a nick there, a stain or whatever. Even with a no-food-or-drink rule it will get violated. Owners will be protective and claim every imagined thing. Taking regular digital photos may help.
• If we talk about letting people park in your garage, that opens up a lot of risk. This may not be workable.
• Odometers will be recorded and entered by cell phone. But there will be discrepencies if there are multiple renters. Cars might have to keep GPS trackers which is privacy-invading.
• Keys have to be left in cars, secured some way that these cars don't become more subject to theft. Or they would need an electronic key added which can start the car with a code entered on a keypad.
• An external keypad is needed to access the car, or possibly a bluetooth device can unlock the doors and the key-box when commanded to by the renter's cell phone. If you know the MAC of the renter's cell phone or headset its mere presence could be enough!

All these things might well mean it's better just to have traditional company owned car-share cars. Or to make it only work among networks of people who know one another. This could be an actual real application for social networks. You might be willing to loan your car to a real "friend of a friend" (not the fake FoFs found on most social network sites.) If a friend has seriously vouched some of the trust issues can be worked out.

Even just taken down to closer friends, it might be found that friends overlap airport trips fairly often. This would probably lead to mostly just taking your own car (or a borrowed one) one way, and using a shuttle or taxi or transit the other way, but that's still a lot cheaper than car both ways and better than shuttle two-ways.

Anyway, interesting to think about.