Hoping to start a national conversation about future transportation needs, the Obama administration released a report Monday that identifies key population, environmental, cultural and technology trends expected to shape the way Americans get from one place to another over the next 30 years.

By then the U.S. population will grow by 70 million, the equivalent of adding another Texas, Florida and New York. Much of this increase will be in cities in the South and West. At the same time, the number of Americans over age 65 will increase 77 percent, and one-third of seniors will have a disability that limits their mobility.

At the same time, the nation's 73 million millennials, the first generation to grow up with the Internet, will become an important economic engine. So far, they are driving less than their Generation X predecessors and many are gravitating to cities where they can bike, walk and take public transit to work or school.

Significant increases in freight shipments are forecast across all modes of transportation — highway, rail, maritime ship and aviation. Already, a 50 percent increase in crude oil production since 2008 is straining the capacity of America's freight railroads.

Transportation Secretary Anthony Foxx sat down to discuss the trends with Google Chairman Eric Schmidt in San Francisco, the hub of the nation's technology sector. Google has been at the forefront of developing technologies that are expected in the next decade to lead to fully automated cars that can be programmed to drive themselves.

"If we don't get ahead of those challenges we're going to find ourselves stuck in traffic for a long time," Foxx said.

The report is not a blueprint for future action, but rather raises questions:

— How will the U.S. build a transportation system that doesn't just let a growing population travel, but lets them travel more safely?

— How will it reduce freight chokepoints that drive up the cost to business?

— How can infrastructure be made resilient enough to weather events like Hurricane Sandy that occur with increasing frequency?

— How can barriers be cleared for new technologies that can make transportation safer and more convenient?

If there are no changes in capacity to the national highway system, recurring peak congestion is expected to increase from 11 percent of the system in 2007 to 37 percent in 2040. That will slow traffic on 21,000 miles of highways and create stop-and-go conditions on another 40,000 miles, the report said.

The report's release comes as Congress is struggling once again to find the money to keep federal transportation aid flowing to states. The federal Highway Trust Fund, which pays for highway and transit aid, has been teetering on the edge of bankruptcy since 2008. Revenue from the federal 18.4 cents-a-gallon gasoline and 24.4 cents-a-gallon diesel taxes are running more than $15 billion a year short of needed highway and transit aid to states.

Congress has kept money flowing through a series of stopgap measures. If nothing is done by May 31, the government will have to slow down payments to states. The uncertainty over whether federal aid can be counted upon has already caused some states to delay transportation projects.

Three blue-ribbon commissions have recommended raising federal fuel taxes, and some lawmakers are backing proposals to do that. But raising fuel taxes is unpopular with the public, and many Republican lawmakers have pledged not to raise taxes.

President Barack Obama has proposed a 31 percent boost in transportation spending. Obama wants to spend $478 billion on transportation and infrastructure over the next six years, including a 75 percent increase for mass transit. Half of that money would come from current taxes on fuels and other transportation fees. Another $238 billion would come from a one-time surge of revenue created by applying a 14 percent tax on profits that U.S. corporations have parked overseas.