MWCOG.org - TPB Weekly Report

January 15, 2013

Solo Driving to Account for Smaller Share of Commute Trips in 2040

Between now and 2040, the share of people who drive alone to and from work each day is expected to fall while the share of people who choose to carpool, bicycle, or walk to work will increase, according to the results of the Transportation Planning Board's latest travel forecasts. The share of people who take transit is expected to remain roughly the same.

In all, the TPB's travel models predict more than a million more daily commute trips by 2040 based on anticipated growth between now and then. The latest forecasts from the Metropolitan Washington Council of Governments say the region's population will grow by 24% -- to more than 6.4 million people -- and that employment will grow by 36% -- to almost 4.4 million jobs.

Most of the new commute trips that are expected -- about 450,000 -- will be made by solo drivers, according to the forecasts. Carpool trips will increase by about 240,000 per day, as will those by transit. Almost 80,000 of the new trips will be made by bicycle or on foot.

Today, 61% of all commute trips in the region are made by solo drivers. By 2040, that number is expected to fall to 57%.

The share of trips by carpool, on the other hand, will increase from 11% to 14%, while the share of trips by bicycle or on foot will increase from 4% to 5%. About 28% of trips to and from work in 2040 will be by transit, the same as today.

These shifts, although they appear to be slight, are an important reflection of emerging trends in how people are likely to choose how to get around the region in the future.

The TPB's travel forecasting models take into account a wide range of assumptions about the relative availability and attractiveness of various travel options in predicting what modes people will choose.

Among other things, the models take into account trip costs and travel time, which include things like transit fares, fuel prieces, parking costs, and tolls, as well as time spent not only traveling but also parking one's car, waiting for buses or trains, transferring between lines, or walking to one's final destination.

Over the next thirty years, the relative availability and attractiveness of different travel modes are expected to change, and those changes are expected to vary throughout the region.

The TPB's forecasts show that in the regional core, for example, which includes the District of Columbia, Arlington County, and the City of Alexandria, the share of people taking transit to and from work is expected to decrease slightly, from 58% to 56%. Meanwhile, the share of people bicycling or walking to work is forecast to rise from 13% to 15%. More housing planned within walking distance of job centers and improvements to bicycle and pedestrian infrastructure are expected to drive such shifts.

In the region's inner suburban jurisdictions -- Fairfax, Montgomery, and Prince George's counties -- more than 400,000 more commute trips are expected by 2040, compared to today. The share of trips by solo drivers will fall from 63% to 61%, while small increases in the share of trips by transit, bicycling, and walking are expected. The travel models predict that the opening of the Silver Line in Virginia and the Purple Line in Maryland, along with the new mixed-use development they are likely to spur, will contribute to such shifts.

Farther out, in Frederick, Charles, Prince William, and Loudoun counties, new transit options like the Silver Line, increasing highway congestion, and new high-occupancy toll lanes are expected to encourage a greater share of people to commute by transit, carpooling, and bicycling and walking. The share of commute trips made by solo drivers is forecast to fall from 79% to 70% in these areas over the next 30 years, while the share of trips by carpool will increase from 15% to 20% and the share of trips by transit will increase from 5% to 9%.

As the region continues to grow, and as its transportation system continues to evolve, the modes of travel people choose to get to and from work will change based on the relative availability and attractiveness of various options. Planners and decision-makers can encourage further shifts by taking steps to make desired modes more available and more attractive to potential travelers.