Flexible Zipcar Algorithm

I am now a proud owner of a Zipcard. My old car died a horrible, screaming death recently and I decided to try to go carless as an experiment, hoping to save some money or to lose weight.

Zipcar is the modern way to rent a car. You reserve a car by the hour or by the day through the web, arrive at the site, swipe your card and drive away.

My biggest problem with being a Zipster is that the closest Zipcar location to my home is about one mile away. On second thought, I am losing weight.

But for other Zipsters, the biggest problem is that you have to return the car at the exact location where you picked it up. Obviously, if you allow renters to return their car to a different location the Zipcar company might run out of paid parking spaces in a particular location or, even worse, the cars might migrate to certain places, leaving other locations without any car.

I would like to propose an algorithm that will add some flexibility to where you can return a car, without overwhelming the system.

Here’s how it would work. Suppose we have three cars currently assigned to the Mt Auburn/Homer Ave location. I suggest we name three as a desirable number, but actually allow from three to four cars to be assigned to this location at any particular time.

Now suppose I want to pick up a car at the Mt Auburn/Homer Ave location and to return it to the Somerville Ave/Beacon location. If the number of currently assigned cars to Mt Auburn/Homer Ave location is three (at the lower limit), the Zipcar reservation webpage tells me, “Sorry, you can’t use this location unless you return your car back here,” and shows me the closest location with extra cars. The same goes if the number of assigned cars at the Somerville Ave/Beacon location is at its upper limit. If my starting point has more cars assigned to it than its lowest limit and my destination point has fewer cars assigned to it than its upper limit, then I am allowed to take a car from my starting location and return it to my destination. Zipcar can throw in some financial incentives. If my choice disrupts the most desirable balance of car assignments, I have to pay a fee. If my choice restores the balance, I get a bonus discount.

It would be so cool if zipcars were flexible. I understand that the average cost to the company of parking each car might go up with my flexible algorithm as Zipcar will need more parking spaces than cars. But Zipcar can start implementing this flexibility with a small number of flexible locations. It would be a great feature.

Hey, Zipcar algorithm designers! Can I get a bonus if you implement my algorithm? I can also design a financial incentives formula for you.



  1. Kevin McLaughlin:

    Wow – love the idea. In all of the discussions about “one way car sharing”, I have never heard a potential solution like this. It also highlights a second huge issue of cars all ending up in the same lot: needing extra parking. Parking is actually one of the biggest monthly expenses – sometimes the biggest – so needing extra (to allow for some movement) adds cost. Your system does reduce the cost of shuttling, though. Again, very nice.

  2. luud schimmelpennink:

    Thania Khovanova
    I work on a system not for car sharing but for networksystems like velib
    there the problem gives more trouble
    many station full that is no place or
    empthy so you can not get a bike.
    I have a algoritme what i like to discus with you
    Luud Schimmelpennink

  3. Tanya Khovanova’s Math Blog » Blog Archive » Floating Zipcars:

    […] I published my ideas for a Flexible Zipcar Algorithm that allows customers to rent Zipcars one-way. I had a dream the night after I published it: the […]

  4. Misha:

    Iuud, can you hire some school kids to ride your bikes from the full locations to an empty ones for some pocket money?

  5. Dave Brook:

    Researchers have looked at the University of California Intellishare program have written extensively about trying to develop such an algorithm – look for papers written by Matthew Barth. Bodo Schwieger in Germany did a project with 20 Smart cars in Berlin allowing one-way service and found that customers were willing to go to other stations to pick up cars – especially when they got a discount. And the recently defunct Honda DIRACC program in Singapore operated for several years with one-way, no reservation trips between 18 stations. And of course there are public bicycle programs allowing one way trips in many cities in the world. The rebalancing efforts are considerable.

  6. Recent Links Tagged With "zipcar" - JabberTags:

    […] public links >> zipcar Zip Car Helps In Saving Gas Saved by aoiro on Sat 03-1-2009 Flexible Zipcar Algorithm Saved by kencookie on Sat 27-12-2008 Zipcars.com — ahead of their time? Saved by XSeed88 on Fri […]

  7. Alejandro:

    Read about drive-now & car2go in Germany a while ago doing something like that. While in Berlin a few weeks back I’ve seen many of their cars parked on the streets, I wonder if you can just leave them around, not even bother going to a designated parking spot.

    It seems drive-now is already in SF: https://us.drive-now.com/how-it-works/?L=2&language=en_US

Leave a comment