Recent years have seen numerous visionary proposals for fixing our transportation system. President Obama and California Governor Jerry Brown want to build high-speed rail. Elon Musk wants to build a hyperloop. Japan wants us to buy its magnetic-levitation technology.

I have a rule of thumb: Any transportation technology that requires new infrastructure is not worthwhile. America has nearly 2.7 million miles of paved roads, 140,000 route-miles of rail lines, 600 commercial and thousands of non-commercial airports that can do all we need them to do.

Although most of our transportation infrastructure is more than 50 years old, there are two good reasons why it will be sufficient to meet most of our future needs.

First, the infrastructure we have was inexpensive to build and goes nearly everywhere. High-speed rail, maglev and other schemes are far more costly per mile and won’t become competitive until they, too, go nearly everywhere.

President Obama’s high-speed rail plan consisted of several disconnected routes totaling about 8,500 miles. Yet in 2011 then-Secretary of Transportation Ray LaHood admitted that building true high-speed lines over all these routes would have cost more, after adjusting for inflation, than the 48,000-mile Interstate Highway System that connects every major city in the contiguous 48 states with the rest of the country. The system would never have carried more than about 1 percent of passenger travel and virtually no freight.

  • Replacing our antiquated air traffic control system will improve airway capacity, and bigger planes can meet increased demand for air travel at no infrastructure cost.
  • By replacing slow human reflexes with computers, self-driving cars will at least double roadway capacities. Until then, cities can improve road capacities with low-cost improvements like traffic signal coordination, freeway ramp metering and fixing bottlenecks.
  • Major new highways will be needed only in fast-growing urban areas and mainly in the suburbs of those areas, where a mile of four-lane freeway can move 10 times as many people as a mile of light rail at a much lower cost.

For speed, planes are twice as fast as high-speed trains yet cost far less. For the cost of a few miles of high-speed rail, we could double the throughput of airport security, saving travelers millions of hours per year.

Want affordable intercity transport without driving yourself? Companies like Megabus offer non-stop service on increasing numbers of routes with Wi-Fi and other amenities, often on schedules that are faster, more frequent and at lower fares than Amtrak. Thanks to Internet ticket sales and other innovations, intercity bus service is growing faster than Amtrak or the airlines.

Want safe, convenient transport? Almost nothing matches the door-to-door convenience of the automobile, and thanks to vehicle stability control, collision-avoidance systems and other safety improvements, auto fatality rates have declined dramatically in just the last decade.

With improvements like these, in 50 years our transportation system will be able to move far more passengers and freight while still relying on the same basic infrastructure.

Americans are constantly told we are “falling behind” Europe and Asia by not building expensive new infrastructure that few people will use. We don’t need to impoverish ourselves to keep up with the neighbors. We just need to maintain and efficiently use the infrastructure we have, making expansions where necessary but relying mainly on new technologies to use it ever more effectively.