## Suburban Ride-Sharing Is Mathematically Impossible

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Does ride-sharing work in the suburbs? Let's do the arithmetic!

The math looks sound. The number of suburban people who would ride share rounds to zero:

• 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.