Vice President Biden delivers the keynote remarks at a conference of transportation experts put on by The Washington Post. (Kate Patterson/For The Washington Post)

Ask a transportation expert what America needs right now and you’ll get a fairly simple answer: better roads and bridges, enhanced public transit and improved rail lines, ports and airports. Ask a transportation expert how Americans will get from place to place in 20 years, and often the answer is a lot less certain.

If that seems like a disconnect — surely what we need today will be in use for a couple of decades — there is a one-word explanation for the quiver in experts’ voices when they talk about transportation’s future:

Technology.

It has revolutionized transportation just as it has forever changed most other aspects of life, and in the years to come it promises to take transportation to a dozen forks in the road.

That was one aspect made clear at a wide-ranging conference of transportation experts brought together in downtown Washington on Tuesday by The Washington Post.

The conference attendees heard from mayors, past and present U.S. secretaries of transportation, Vice President Biden and a bevy of fellow experts, most with their own vision of the future.

The central theme for most was the critical importance of investing in the nation’s tattered infrastructure to keep the United States competitive in the global market. Finding the funding to do that as revenue from the traditional gas tax dwindles was a subset of that conversation, with several suggesting a move to a mileage-based fee or tolling on interstate highways.

When it comes to a vision for the future that lies just over the horizon, there were many ideas tossed out that made certainty a bit elusive.

Technology has spread so rapidly through virtually all modes of transportation that the challenge is in determining how it will continue to transform the future. At few times in history has the pace of change come so quickly.

Questions that arose — without firm answers — from the presentations Tuesday included:

●If autonomous vehicles — driverless cars — are just over the horizon, will drivers who no longer drive still need insurance? Or will vehicles and their manufacturers be covered by product-liability policies?

●Will highways of the future need things such as road signs or guardrails, since the cars know where they are going and will stay between the white lines?

●If electric cars are a major part of the future — Tesla was represented at the conference — will there still be a need for a gas station every few blocks?

●With autonomous cars able to toddle off and park themselves, will there be a need for vast acres of underground parking garages in downtown areas such as the District’s where land is at a premium?

●When the last parking meters wear out and disappear, and cars begin to park themselves and pay for the space electronically, will parking tickets become a thing of the past? And what will replace the ticket revenue that cities have come to count on?

●Will public transit be less popular when autonomous cars can deliver their passengers that “last mile” from the transit stop to the front door?

●Will magnetic levitation trains running through tunnels deep underground carry passengers at 300 mph?

●And will cars fly?

A prototype of a flying car sat on 14th Street NW outside the conference.

“Hopefully we can use these technologies we’ve talked about here at the conference and change some things,” said flying-car developer Carl Dietrich, head of Terrafugia, whose Web site says that it “intends to lead the creation of a new flying car industry.”

In an allusion to the prospect that packages may be delivered to homes by unmanned drones, Dietrich asked: “How many years will it take of seeing your packages flying above you before we say, ‘Hey, we could be up there?’ ”