CTS research associate Gary Barnes gave a presentation on "Density and Travel Choices in U.S. Cities" at the TRG Study workshop held April 12.

Barnes said that large U.S. cities exhibit surprisingly large variations in both urbanized area density and in vehicle miles traveled (VMT) per person per day. What accounts for the large differences in VMT? Barnes explained that he hoped to identify land use and other policies that might answer this question. To understand the disparities in travel, Barnes considered such factors as road per capita, transit share, congestion, average speeds, and density for the Twin Cities and other large U.S. cities.

He suggested using travel time as possibly a more useful way to evaluate system usage. Time better represents personal costs: "The main cost of a mile is the time it takes," he said. It may also be more closely related to social costs such as congestion and pollution.

People who travel spend 65 to 70 minutes a day on the road regardless of mode. This number may increase in large cities and outlying areas; however, "it never seems to really decrease," Barnes stated. While dense parts of cities have less auto travel, this comes from increased transit use rather than less travel overall.

Two groups of people are more likely to use transit, Barnes said. "Workers traveling downtown are as much as eight times more likely to use transit, and low-income households are two to three times more likely to use transit." But surprisingly, neither reduced VMT nor higher transit use is correlated with reduced congestion.

It will be important to learn lessons from cities that are less reliant on driving, Barnes said. Some ideas for further research include studying specific cities with fewer vehicle miles traveled, continuing to explore the link between density and transit use, and extracting lessons specifically applicable to the Twin Cities.

"Strategies to reduce total travel are unlikely to work, but changes in mode choice are possible," Barnes predicted. To make transit more appealing for higher income work trips, travel must begin or end in high density areas. While much discussion focuses on residential density, high commercial density might be a more viable, and equally or more effective, option.