Carpooling, Autonomy, and the Future

What can carpooling reveal about the future for autonomous vehicles?

Glistening glass-topped cars rocketing to and from newly-built downtown towers: whether 1950 or 2018, predictions for our self-driving future haven’t changed much. In our just-around-the-corner future, one vision reigns: groups of people zip from the suburbs to their city jobs and back again, enjoying entertainments in a driverless car.

Although some highly-limited self-driving vehicles are available in a handful of markets today, human-driven cars are everywhere. We can use information about how people use cars today— especially when they choose to carpool and share their cars with others — to add some more detail and dimension to visions of our autonomous future.

How do people use cars today?

Let’s look at commuters first. Simply stated, three of every four commuters drive to work alone. Only one in ten commuters carpools to work.

I was quite surprised to learn that carpooling remains such a popular choice for commuters. Even accepting a loose definition of carpools that might include family or children, I did not expect that carpooling would be twice as popular as transit. Also interesting: carpooling used to be even more popular. Around 20% of commuters carpooled in 1980.

Over 13,500,000 people in the United States share transportation to and from work. Three of every four carpoolers share commutes with one other person:

Only about 1,300,000 commuters, or under 1% of all commuters, report sharing a carpool with four or more people to get to work.

Where do people carpool?

Most cities share a similar distribution of commute transportation choices: 80% of commuters drive alone, 10% of commuters carpool, and 10% make other choices, including walking, biking, or working from home.

Mapping these commute choices reveals some surprising clusters of carpooling commuters. Let’s look at the percentage of carpoolers in Census Tracts in some major cities in the country. Darker purple areas indicate more carpooling commuters; major highways are highlighted in red-orange. First up: New York City.

In the city itself, note the concentration of carpoolers in Flushing, Queens. Maybe this has some relation to the area’s proximity to major thoroughfares such as the Throgs Neck Bridge, Whitestone Bridge, and Long Island Expressway? Outside of the city, we see carpoolers in Newark, Patterson, up in Peekskill and over in Brentwood (near Islip). Also notable: the lack of carpoolers in other places like Huntington that would seem to have similar highway access and socioeconomic conditions as communities that carpool.

In Chicago, the transit system creates an obvious lack of carpoolers north, south, and west of downtown, despite the close-by interstate highways. There are also few carpooling commuters north of downtown in the city’s wealthier areas. However, we see more carpooling commuters southwest of downtown in a poorer and nonwhite area of Chicago.

Many major cities exhibit their own unique concentrations of carpoolers. Here are maps of nine more metropolitan areas, each with their own unique distribution of carpooling commuters:

Why do people carpool?

Survey data about why people carpool is hard to find. However, in 2006, the Transportation Research Board conducted a survey of over 4,000 commuters in Dallas and Houston, Texas. The survey’s responses provide some perspective.

Reasons for carpooling

In the survey, carpooling commuters (around 600 individuals) were asked to select and rank the reasons they choose to carpool. The top reason the participants selected surprised me:

Access to HOV (High Occupancy Vehicle) lanes

I would have expected commuters to have ranked some of these other popular reasons higher than HOV access:

Enjoy travel with others

Help environment and society

Travel time saving

Sharing vehicle expenses

Another surprise from the survey: although increased productivity and less stress are often offered as primary benefits from self-driving cars, only 10% of people surveyed selected these two reasons for carpooling:

Relaxation while traveling

Get work done while traveling

Reasons for not carpooling

The same survey asked around 3,000 commuters why they didn’t carpool. The top four responses were:

Location and schedule limitation

Travel flexibility

Need a vehicle during the day

Need to make other stops during the trip

Who do people carpool with

Not all carpoolers commute with coworkers. In fact, few do:

Nearly half of all survey participants reported carpooling with adult family members. When you add carpools with children, nearly two-thirds of carpoolers say they share with family. For other carpools, destination proximity (“nearby coworker”) appears more important that origination proximity (“neighbor”).

What We Can Learn

Even in light of some cursory research, our vision of “groups of people zipping from the suburbs to their city jobs and back again” hardly seems to capture the complex needs of different commuters.

• When the majority of commuters choose to drive alone, when the majority of carpoolers report only sharing their vehicle with one other person, and when the majority of carpoolers commute with family members, it seems quite possible that people don’t like to commute with strangers and would very likely rather commute alone.
• However, decisions about transportation infrastructure appear to have a real impact on the choices that commuters make and can encourage commuters to share transportation. Again, the primary motivator for Texas carpoolers was HOV lane access.
• Every city is different. Distance, highway and transit access, socioeconomic components, and cultural factors all combine to create pockets of carpooling commuters in cities. Transportation network companies like Uber and Lyft would do well to understand these pockets and super-serve these carpoolers.
• Motivations for carpoolers suggest new value propositions for future transportation services. Imagine a service that emphasizes social interaction while commuting, another that provides users the most ecologically-friendly transportation options, or another that emphasizes the amount of money that the user saves sharing transportation.
• Finally, the core commuting unit appears to be the family and not the lone city-bound bread-winner. Companies that build transportation services around the needs of a family — including traveling to multiple destinations, changing schedules, chaining commutes with stops for errands, and storing ephemera — will differentiate themselves while appealing to a larger market.

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