The Hard Math of Suburban Carpooling


Uber Pool and other startups like Bridj and Leap talk about using technology to match carpoolers who want to avoid the hassle of congestion, but the Atlantic’s Eric Jaffe reports on smart mobility consultant Steve Raney of Cities21‘s recent thought experiment: “Suburban Ridematch Needle in the Haystack Problem.”

Raney’s assumptions and conclusions:

  • You have 10,000 people working in downtown Palo Alto.
  • A zipcode in nearby Redwood City with a population of 31,500 residents is home to the largest share of commuters who work in downtown Palo Alto:500.
  • If 10 percent of these commuters were willing to carpool to work, as per national averages, then the demand for a ride-share service is at most 50 people a day. (And that’s a generous assumption, since the vast majority of carpoolers are family members or coworkers, as opposed to complete strangers.)
  • If all 50 of these workers keep normal hours with standard morning commutes—again, a generous assumption—then they would all head to the office in a two-hour window. But since not everyone leaves for work at the same time, that window should be broken up into segments. Raney uses six 20-minute segments for the two-hour peak commute period.
  • The six segments turn Redwood City’s 50 potential ride-share users into groups of about eight. In other words, eight out of 31,500 people in Redwood City might be matched for a carpool into downtown Palo Alto on any given morning.
  • If there are even just two competing ride-share services, that number halves to four out of 31,500.

Can a startup work with essentially zero percent of its market?

3 thoughts on “The Hard Math of Suburban Carpooling

  1. The simple issue with pooling is “who are you going to get?” who lives where you live; is going where you’re going and when you are going? the odds of that have gotten worse and worse over the years. the fampool , the HOV lane and the really long distance large employment sites (think car plant in Kentucky) are what’s left. carpooling collapsed in the recession because the two main sources of pooling — home construction and factory work were the hardest hit. Alan

    1. Zman Carpooler

      Carpooling is seeing a resurgence due to the high costs of commuting for work. People are strapped for cash and carpooling offers an economical solution that’s far better than the bus or subway.

      Carpooling suffers from mostly logistical issues. It’s hard to coordinate, share costs properly and for people to get along. If you’re disciplined and not so selfish, it can work.

  2. Zman Carpooler

    Of the 10,000 people in Palo Alto, only 500 commute from one specific zip code? I doubt that. In our 155 person company, I found 7 people (4.5%) in my area, 37 miles away, who want to carpool. I had to reject 2 of them since our carpool is full (5 people). These are just the ones I was able to get in our medium sized company with one poster in the lunchroom. I’m sure there are way more employees in my zip code but HR can’t release employee info to confirm.

    Most people commute long distances because they can’t afford to live near where they work. They’re all potential carpoolers. Even the ones that take the bus!

    I honestly don’t think your numbers work. You say 0.012% , mine says 4.5%. The difference is so large that my real world currently operating carpool says your hypothetical numbers are off.

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