Foon Rhee

The Numbers Crunch: Caltrans says if you build new roads, traffic will come

Construction workers wrap up work on the Fix50 project in Sacramento in June 2014. Research says that new and widened highways are quickly filled with new traffic.
Construction workers wrap up work on the Fix50 project in Sacramento in June 2014. Research says that new and widened highways are quickly filled with new traffic. Sacramento Bee file

We’re well into the busy holiday travel season, so many Californians are getting a bumpy reminder of how decrepit and crowded many of our highways are.

Many might be frustrated that the governor and Legislature haven’t been able to cut a deal during a special session on transportation, though the repair backlog is estimated at $78 billion for local roads and another $59 billion for state highways.

But what if Caltrans is questioning the whole logic of building more roads to relieve traffic congestion? You might think that after reading a policy paper that the department is linking to on its website.

Constructing new roads and adding lanes doesn’t ease congestion for very long because traffic quickly increases to fill the new capacity, concludes the policy brief from the National Center for Sustainable Transportation.

It’s a theory called “induced travel,” basically the transportation version of the law of supply and demand. Adding capacity cuts travel time, thus lowering the “price” of driving and leading to an increase in driving. In the paper, UC Davis professor Susan Handy writes that increasing a road’s capacity by 10 percent is likely to increase vehicle miles traveled by 3 percent to 6 percent in the short run and 6 percent to 10 percent in the long term, basically offsetting any gains.

In her review of the research, Handy also cautions that new and widened roads don’t lead to net increases in jobs or economic activity – not what industry and labor groups pushing for highway construction want to hear. And she warns that a rise in vehicle miles traveled would substantially increase greenhouse gas emissions.

So does the California Department of Transportation endorse the paper? The answer is “yes” – with some explaining.

The official line is that “solid science” shows that expanding roads does lead to more driving, so the department is first fixing existing roads and only building new roads “strategically.” Caltrans also touts its “sustainability” push that encourages bicycling, walking and mass transit.

Caltrans’ policy, according to a spokesman, is for any increase in vehicle miles traveled to stay below the state’s population growth. Its goal is to reduce vehicle miles traveled by 15 percent from 2010 levels by 2020.

But according to its own counts, that number is rising – by nearly 3 percent through September compared to last year – and has risen every year since 2008 except one.

Its policy, however, does keep Caltrans in tune with Gov. Jerry Brown’s crusade to put California at the forefront of adapting to climate change. That includes reducing carbon pollution spewed by cars and trucks, as well as increasing renewable and clean energy.

Brown, who is headed to Paris for the United Nations summit on global warming, suffered a defeat on his most recent climate change bill when Big Oil forced him to spike a key provision that would have set a target of reducing gasoline use by 50 percent by 2030.

Yet if Caltrans does manage to cut vehicle miles traveled, gasoline purchases will surely decline as well.

By being part of the climate change team with the governor, Caltrans could eventually have fewer projects to oversee and less work to do. A government agency not expanding its empire – now that would be a new one.

By the numbers

Vehicle miles traveled on California state highways:

  • 2008: 176.32 billion, down 3.5 percent
  • 2009: 178.29 billion, up 1.1 percent
  • 2010: 178.80 billion, up 0.3 percent
  • 2011: 176.84 billion, down 1.1 percent
  • 2012: 177.26 billion, up 0.2 percent
  • 2013: 180.56 billion, up 1.9 percent
  • 2014: 185.32 billion, up 2.6 percent
  • 2015 (through Sept.): 143.67 billion, up 2.8 percent

Source: Caltrans