Where — and how much — traffic congestion will grow is part of new research into what the D.C.-Baltimore region will look like in 20 years. (Jose Luis Magana/AP)

Curious about what the Washington-Baltimore region might look like in 20 years? Researchers at the University of Maryland say they’ve found a new way to predict how much traffic congestion will worsen, where people will live, and what they’ll pay for housing.

The future, they say, lies in how quickly — and how much — residents begin using autonomous vehicles, whether gas prices rise or fall and where governments allow growth to occur. To see how those forces could play out, researchers at the university’s National Center for Smart Growth Research and Education used a new combination of integrated computer models to come up with four possible scenarios.

The project — known as Presto — is noteworthy, they say, because it looks at the entire Washington-Baltimore region and considers impacts that aren’t typically included in such forecasts, such as air and water quality and how accessible transit is for transit-dependent people. Most such forecasts, they say, look at urban areas separately rather than regionwide. This study also is one of the first to gauge the potential impact that driverless vehicles and changing gas prices would have on how the region grows, they say.

“Usually planners model desired futures,” said Uri Avin, a research professor at the center. “We’re saying we need to think about what might affect us, not only what we want.”

The researchers plan to share their findings with local planners and public officials, including Maryland Gov. Larry Hogan (R) and former Maryland governor Parris N. Glendening (D), in Annapolis on Wednesday.

Gerrit Knaap, executive director of the National Center for Smart Growth Research and Education, said the analysis showed some things that probably seem obvious. For example, if it’s cheaper and easier for people to drive, they’ll drive more and live and work farther out. But he said the findings also reveal the need for more cooperative land use planning for the entire corridor because how local officials allow one jurisdiction to grow affects others.

“There’s been no attempt to really look at the D.C.-Baltimore region in as serious a way as we have,” Knaap said. “We are in fact an increasingly integrated region. … When you don’t plan at a regional scale, you may end up with land use patterns that benefit no one.”

The four scenarios compare to “baseline” assumptions of how the corridor and surrounding areas, including the Delmarva Peninsula, are likely to grow under current government policies. The baseline assumes traffic congestion will worsen “significantly,” particularly on both cities’ beltways and on highways connecting the two. Moreover, housing prices are expected to rise as areas such as Montgomery and Baltimore counties begin to bump up against their self-imposed growth restrictions.

Here are the four scenarios the researchers considered — they gave each one a name — and what the models showed would happen in each, compared to the baseline assumptions:

1. Revenge of the Nerds: Gas prices are low, government doesn’t regulate growth as much, and people embrace autonomous vehicles.

What happens: The economy booms, and people drive more. However, because roads can carry more driverless vehicles traveling closer together, traffic congestion actually improves dramatically. Even so, because driving is convenient and relatively inexpensive, people and jobs move farther out, and transit ridership drops “precipitously.” Cars are more fuel-efficient, but greenhouse gas emissions and other pollution worsen. Because people move farther out, more farmland and forest becomes developed.

2. Free for All: Gas prices are relatively low, and governments allow building in the agricultural preserves of Montgomery, Prince George’s, Fairfax counties and others. There are no major improvements in transit, but toll lanes are built on outer beltways, and another bridge is built to the Eastern Shore.

What happens: New “rural subdivisions” pop up in the agricultural preserves. Housing prices drop significantly, except on the Delmarva Peninsula because it’s become more accessible via the new bridge. With more jobs and homes moving to the suburbs, people commute shorter distances, which improves traffic. Congestion is also relieved as tolled lanes on the outer beltways take some traffic off other roads. Transit ridership drops significantly.

3. Blue Planet: Gas prices rise, stimulating investments in transit and renewable energy, and “green technology” takes off, making zero-emission vehicles more popular and affordable. Autonomous vehicles aren’t widely in use yet, and transit is expanded. Residents’ preferences for an urban lifestyle spurs growth in Baltimore, both cities’ inner suburbs, and outer suburbs around transit stations.

What happens: Researchers say this scenario is the most sustainable. Traffic congestion drops as new jobs and housing are built closer together, and people can use transit more. Housing prices remain steady as additional housing is built in the inner suburbs. People drive less, and the high number of zero-emission vehicles leads to far less air pollution. As D.C. and the inner suburbs run out of available land, growth “leapfrogs” preserved agricultural areas and eats up more forest. Technological advances, however, leave less pollution running off into local waterways.

4. Last Call at the Oasis: Shrinking world supplies of oil cause gas prices to quadruple. Economic growth slows, household incomes fall and the cost of driving increases dramatically. Governments direct growth toward the urban cores and invest in transit, as well as infrastructure for electric vehicles.

What happens: People drive much less, and traffic gets far less congested, while transit ridership increases significantly. Greenhouse gas emissions fall dramatically. Researchers say they’re surprised to find that more new households don’t appear in Baltimore and D.C. Instead, people are attracted to transit-accessible inner suburbs known for good schools and low crime. Housing prices are slightly lower than the baseline because there’s more capacity in the desirable inner suburbs.

Here’s how the potential outcomes look in maps. RON, in purple, stands for Revenge of the Nerds (#1 above); FFA, in orange, stands for Free for All (#2); BP, in blue, stands for Blue Planet (#3), and LCO, in green, stands for Last Call at the Oasis (#4).

Here is where researchers predict traffic congestion under each scenario. (Graphic design by Paste In Place)

Here’s where researchers believe housing will get more or less expensive under each scenario. (Graphic design by Paste In Place)

The researchers say they now plan to test different strategies for the most sustainable ways the region could grow.

For example, they say, governments could offset the impact of more driving from autonomous vehicles by providing more driverless transit or financial incentives for ride-sharing. Or they might reduce pollution by offering subsidies or incentives for zero-emission vehicles and expanding the number of charging stations throughout the region.

They also note that each scenario has its pros and cons. Allowing more development in agricultural preserves would significantly lower housing costs, they say, but would mean losing green space and farmland. Another scenario that would enable people to drive more would produce higher greenhouse emissions, but some people would enjoy more personal freedom in how they get around.

Click here to see the Presto report.