Transportation agencies are facing the consequences of induced demand

Induced demand. It’s a concept that used to be popular only among the wonkiest transportation experts, and now gets covered by outlets ranging from the Washington Post to the Wall Street Journal. Governing calls it “the almost universally accepted concept” that almost no one understands, while Strong Towns calls ignorance of the concept “professional malpractice.” With new tools and a better understanding emerging, some transportation agencies are now beginning to wrestle with the implications.

Partially automated vehicles increase VMT

Numerous studies have raised concerns that self-driving cars could flood our roads with more traffic, as commuters travel longer distances and cars drive themselves in and out of central cities to avoid parking. Fully autonomous vehicles are probably a ways off, giving policymakers time to grapple with the potential impacts, but new research suggests that even common features found in cars today like adaptive cruise control and lane guidance lead to increased vehicle miles traveled.

The value of travel speed is not what we often think

People will pay more to reduce the amount of time they spend getting from one place to another, according to a principle known as “value of time.” So naturally, it would make sense that moving people faster would offer the same benefit. However, a new study suggests that increased speeds do not translate to shorter travel times and speed doesn’t have the same value as time.

Gas prices can have ripple effects on development patterns and travel options

Gasoline prices have clear impacts on development patterns, according to recent research that adds new evidence for the long-term impacts of transportation pricing signals. The new study shows that wage growth and low gas prices contributed to high rates of suburban growth in the 1980s and 1990s, measured in terms of deforestation. Those trends have reversed as gas prices have risen.

Aligning priorities across agencies

Government agencies sometimes face the criticism that they have difficulty coordinating between various silos. In the transportation sector this may stem, in part, from the historic approach of separating modes into different funding, maintenance, and development streams. While barriers still exist, some agencies are developing coherent multimodal policy to combat this. In other cases incoherence can occur when different segments of the same network fall under the jurisdiction of different agencies, each with its own priorities and maintenance approaches.

Small pricing signals can help cut traffic

Transportation agencies historically have sought to cut congestion by adding capacity. Alternatively, modest pricing signals could be more cost effective and efficient at managing demand, saving public agencies much more in the long run. One example is the I-65 bridge spanning the Ohio River between Kentucky and Indiana. The bridge carried close to 140,000 vehicles per day prior to construction. The two states spent about $1 billion to increase the capacity of the crossing from six lanes to twelve, enough to handle up to 250,000 vehicles per day. To recoup some costs, a toll of less than $3 per trip was instituted, discounted for regular commuters. Once tolling began in 2017, daily trips dropped to about 60,000.