My family and I are gearing up for about 3,000 miles of driving while on vacation over the next week and a half. I don’t like driving that much, so I was thinking about other ways I could have reduced fuel consumption and energy use for my trip. It turns out that the car is probably the most energy efficient and practical way to go.
We drive a Honda Civic. It gets about 30 MPG in the city, 35 MPG on freeways, and sometimes up to 38 MPG if I’m doing 60 MPH for a long time on a road like US-30 in Indiana. The car will be pretty full on this trip and we’ll be driving faster than normal in the wide open spaces of South Dakota and Wyoming, but even if we get 30 MPG on average, we’ll be getting 90 passenger-miles per gallon for the three of us. This works out to 1,389 BTU per passenger-mile according to calculations from the Bureau of Transportation Statistics (see the notes at the bottom). How does that compare to other modes? From the same BTS table:
| Mode | BTU/Pax-Mile |
| Our Car with 3 Passengers | 1389 |
| Our Car with 1 Passenger | 4167 |
| Average Motorcycle | 1742 |
| Amtrak | 1745 |
| Transit Bus | 2656 |
| Air (Domestic Operations) | 2931 |
| Average Car | 3501 |
| Average SUV/Truck | 3980 |
Even the average motorcycle and Amtrak train can’t compare to the energy efficiency of putting three people in a small sedan. This fact seems to be often overlooked by people like me who promote the virtues of transit on a daily basis. Perhaps transportation planners need to think much harder about how to promote car-pooling as an integral part of our transportation and energy solutions. Nearly every MPO has a ride-share program, and there are a couple of web sites that try to connect people, but is that really enough? What else can be done to promote car-pooling? What metropolitan areas are already doing well?
To try to answer these questions, I turned to the US Census. The following table shows overall car-pool mode share for journey to work trips and the percentage of auto commuters car-pooling in the 50 largest US metropolitan statistical areas. The data source is the 2006-2008 US Census American Community Survey.
| Pop Rank | Metropolitan statistical area | Car-Pool Work Trip Mode Share | Car-Pool Commuters / All Auto Commuters |
| 14 | Riverside-San Bernardino-Ontario, CA | 14.6% | 16.1% |
| 12 | Phoenix-Mesa-Scottsdale, AZ | 13.7% | 15.5% |
| 35 | Austin-Round Rock, TX | 13.3% | 15.2% |
| 48 | Salt Lake City, UT | 12.7% | 14.4% |
| 15 | Seattle-Tacoma-Bellevue, WA | 11.7% | 14.3% |
| 8 | Washington-Arlington-Alexandria, DC-VA-MD-WV | 11.0% | 14.2% |
| 25 | Sacramento–Arden-Arcade–Roseville, CA | 12.3% | 14.0% |
| 13 | San Francisco-Oakland-Fremont, CA | 10.1% | 13.9% |
| 6 | Houston-Sugar Land-Baytown, TX | 12.6% | 13.9% |
| 46 | New Orleans-Metairie-Kenner, LA | 12.2% | 13.5% |
| 2 | Los Angeles-Long Beach-Santa Ana, CA | 11.4% | 13.4% |
| 30 | Las Vegas-Paradise, NV | 11.8% | 13.1% |
| 28 | San Antonio, TX | 11.9% | 13.1% |
| 23 | Portland-Vancouver-Beaverton, OR-WA | 10.7% | 13.0% |
| 33 | Charlotte-Gastonia-Concord, NC-SC | 11.6% | 12.8% |
| 1 | New York-Northern New Jersey-Long Island, NY-NJ-PA | 7.4% | 12.8% |
| 17 | San Diego-Carlsbad-San Marcos, CA | 10.9% | 12.7% |
| 4 | Dallas-Fort Worth-Arlington, TX | 11.5% | 12.6% |
| 9 | Atlanta-Sandy Springs-Marietta, GA | 10.9% | 12.4% |
| 49 | Raleigh-Cary, NC | 10.9% | 12.0% |
| 44 | Oklahoma City, OK | 11.0% | 11.8% |
| 21 | Denver-Aurora-Broomfield, CO /1 | 10.1% | 11.8% |
| 47 | Birmingham-Hoover, AL | 11.1% | 11.7% |
| 40 | Jacksonville, FL | 10.7% | 11.7% |
| 3 | Chicago-Naperville-Joliet, IL-IN-WI | 9.1% | 11.4% |
| 20 | Baltimore-Towson, MD | 9.7% | 11.4% |
| 41 | Memphis, TN-MS-AR | 10.6% | 11.3% |
| 31 | San Jose-Sunnyvale-Santa Clara, CA | 9.8% | 11.3% |
| 38 | Nashville-Davidson–Murfreesboro–Franklin, TN | 10.4% | 11.3% |
| 7 | Miami-Fort Lauderdale-Pompano Beach, FL | 10.0% | 11.3% |
| 27 | Orlando-Kissimmee, FL | 10.1% | 11.1% |
| 43 | Richmond, VA | 10.2% | 11.1% |
| 36 | Virginia Beach-Norfolk-Newport News, VA-NC | 9.8% | 11.0% |
| 5 | Philadelphia-Camden-Wilmington, PA-NJ-DE-MD | 9.1% | 11.0% |
| 42 | Louisville/Jefferson County, KY-IN | 10.1% | 10.9% |
| 22 | Pittsburgh, PA | 9.4% | 10.8% |
| 19 | Tampa-St. Petersburg-Clearwater, FL | 9.5% | 10.6% |
| 10 | Boston-Cambridge-Quincy, MA-NH | 8.0% | 10.3% |
| 29 | Kansas City, MO-KS | 9.3% | 10.1% |
| 37 | Providence-New Bedford-Fall River, RI-MA | 9.0% | 10.0% |
| 16 | Minneapolis-St. Paul-Bloomington, MN-WI | 8.7% | 10.0% |
| 18 | St. Louis, MO-IL | 9.0% | 9.9% |
| 34 | Indianapolis-Carmel, IN | 9.1% | 9.8% |
| 39 | Milwaukee-Waukesha-West Allis, WI | 8.7% | 9.7% |
| 24 | Cincinnati-Middletown, OH-KY-IN | 8.8% | 9.7% |
| 50 | Buffalo-Niagara Falls, NY | 8.4% | 9.4% |
| 11 | Detroit-Warren-Livonia, MI | 8.5% | 9.1% |
| 45 | Hartford-West Hartford-East Hartford, CT | 8.2% | 9.1% |
| 32 | Columbus, OH | 8.0% | 8.9% |
| 26 | Cleveland-Elyria-Mentor, OH | 7.8% | 8.7% |
First, let’s note that of the Columbus is ranked 49 out of 50, right above Cleveland, so obviously there is room to improve. Second, population rank doesn’t seem to correlate well, so it’s probably not about traffic in large cities or the high cost of parking.
I tested the route-miles of high-occupancy-vehicle (HOV) facilities per capita too. That correlates a little better, but it’s still not a strong relationship:
So what gets people to car-pool? Any ideas?
How can Columbus specifically increase its car-pool percentage? Should there be HOV lanes on the freeways? Should there be some kind of parking incentives? Do employers need to take a more active role?
Great post! I think some big factors in the decision to carpool is whether you 1) live close to your co-workers, 2) enjoy spending time with co-workers, and/or 3) whether you have kids (regardless of whether you’re married). People aren’t willing to drive all over the city to pick up others first thing in the morning. People who hate their job and/or dislike their colleagues won’t want to spend any extra time with them. And of course, if all you use your car for is to get to and from work (that is, not picking up kids, running a bunch of other errands, etc.) then it’s a lot easier to give up the daily drive.
I knew a few people at work who carpooled (myself not included, unfortunately) and they were all young, unmarried, and lived in roughly the same neighborhood (or were at least along the same route.) To me, they were a good example of the typical carpool profile.
Would be interesting to see correlation between average commute times and carpool percentages. e.g. Longer commute times lead to more carpooling. Commute times don’t always correlate to population rank because of bottlenecks like bridges, number of accidents, etc.
Can tell you from my personal experiences that HOV lanes are a real incentive to carpool in Bay Area. The incentive isn’t as much to save fuel or be more green though as much as it is to save time.
I can do that, but not until I get back from vacation.
Thanks for the comment.
Well, only because the average Amtrak train has low ridership. If you packed it three-quarters full, it would blow your sedan away, and so would the “transit motor bus.”
We promote transit not because we’re mistaken about its efficiency, but because the more people that ride transit, the more efficient it is.
^Agreed on all counts cap’n. This isn’t intended to be a slight against transit. I’m just pointing out that I think car-pooling can do a lot of good, and is often overlooked by transportation professionals such as myself. Nevertheless, to get 120 pax-mi/gallon with a bus (the equivalent of four people in a 30 MPG car), we need about 35 passengers on the bus.
[...] from around the network: Xing Columbus writes in praise of car-pooling. M-Bike.org has some news about more funding for the Underground [...]
[...] from around the network: Xing Columbus writes in praise of car-pooling. M-Bike.org has some news about more funding for the Underground [...]
Great post! I think carpooling is often overlooked as part of the sustainable transportation picture because it’s really not that flashy – it’s harder to notice the benefits of getting more people in one car than it is to see a new bus hit the road or a new bike lane put down.
Carpooling as a component of a multi-modal trip is important, too, and where DOTs can help with this is the implementation of more park-and-rides, either through new construction or, preferably, through partnerships with well-placed sites with plenty of excess parking (like strip malls or big-box stores). Driving to point A and connecting to transit or bike options is an option that most drivers have at their disposal already without the expense of implementing new transit service.
In our region, which is a mix of small urban and rural, carpooling is the only option most people have until they get into the urban area. Fortunately, since most employment is in the urban core, it makes the logistics of forming carpools easier – most commuters eventually funnel into a handful of high-traffic corridors. Finding meeting space for them is the main problem/
I wrote about carpooling last year. I think, unfortunately, that more people don’t do it because of perceived coordination issues. From that perspective, I can sympathize, and it’s the reason I support public transit and bicycling facilities as the best means of alternative transportation.
[...] from around the network: Xing Columbus writes in praise of car-pooling. M-Bike.org has some news about more funding for the Underground [...]
The common denominator to all transit options: bicycle use, car sharing, greater utilization of the bus option, avoidance of downtown parking and congestion are all facilitated by greater use of those legally proscribed spaces (at retail establishments) whose initial intent is to make the world safe for cars. Why not use their strength against them?
If you drive a manual, then through the gears as quickly as possible without using the engine. Reduce your air conditioning use in the car, and low speed is a significant increase in the amount of fuel required for these systems macht. Stick to speed limits on the road you’re on. The faster you drive the more fuel you use. These steps, if followed correctly will lead to better fuel efficiency and reduce over all the bills.