The typical American driver could save $1,800 a year by giving up his or her car and taking the train or bus to work.
But there is no such mass transit option for many people.
Such systems only make sense in dense urban areas and, even then, they are often heavily subsidized and only replace the car for some.
Rick Remington, a transportation researcher at Rutgers University in New Jersey, said that a public transit system has to be near cities in order to work.
"It's got to be frequent service, it's got to be convenient, it's got to be fast and it's got to have the population density to support it," he said.
High gas prices are drawing a record number of travelers to public transit systems. But this is just the latest spike in a decade-long rebound of buses, subways and trains, Remington said.
"This isn't just something that arrived with high gas prices," he said. "It's been going on since by the mid-90s. A lot of it was being driven by congestion."
Basically, Remington said, people were fed up. They realized they were losing a good part of their day just sitting in traffic.
LeeAnne Hays, who lives in suburban Kansas outside Kansas City, is one of the new converts to public transit.
She used to drive 17 miles each way, each day to her job, taking the bus on occasion. But as gas prices started to climb, she decided it was time to make a full-time switch.
Hays now drives three miles to the nearest bus stop and takes the bus the rest of the way. It only saves her about $7 a week on gas — not including wear and tear on her car — but she doesn't have to personally deal with traffic.
"Usually, I rest, or read or do something much more pleasant than fighting traffic," Hays said. "For me, I really believe it's a lifestyle change. I detest traffic."
Hays is not a morning person and it takes some self-discipline to get to the bus stop on time. But, she said, "frankly, it has been a fairly painless transition."
Even if gas prices retreat — which Hays believes in unlikely — she will still ride the bus.
"People are still making fun of me in the office for taking the bus, but I don't care," she said. "I'm trying to convince them I'm the hip one."
There are more than 10 billion trips taken on public transit in this country each year, according to American Public Transportation Association, the industry's lobbying and trade group.
While that might seem like a lot, there were 23.4 billion trips back in 1947.
But that all started to change after World War II.
"That's when people left the cities for the Levittowns, the suburban growth which is more dispersed and is auto-centric," Remington said. "The development was based on cheap gas and an automobile society."
Ridership hit a low of 6.5 billion trips in 1972.
"That is now boomeranging," he said. "Gas isn't cheap anymore and the housing markets that are most hurt are those furthest from employment centers. The further you are from your job, the harder it is to sell your house."
Most public transit riders in America still take buses, which account for 60 percent of all rides. Buses use existing roads but also face the pitfalls of traffic. The big recent growth in transit has come from light rail systems, which are cheaper to build than traditional trains and can access smaller markets.
"What's interesting is the real spikes in ridership that have been occurring in Nashville and Santa Fe, places that five, 10 years ago you would never have been associated with public transit," Remington said.
Some riders turn to public transit for environmental or logistical reasons. But with gas now costing more than $4 a gallon, many people are doing so for economic reasons.
The American Public Transportation Association calculates that at $4 a gallon, somebody with a 24-mile daily roundtrip commute will save $1,840 a year by taking public transit. (The figure includes the cost of gas and parking.)
That figure is also based on a $3.50 roundtrip transit expense.
Most public transit systems are only able to keep their fares that low because of heavy subsidies from the government.
Transit advocates point out that every form of transportation receives a subsidy.
"Highways aren't self-supporting either," Remington said. "Gas taxes cover less than 60 percent of the cost of their operation and maintenance."
For mass transit, 32.4 percent of the actual operating costs for all systems across the country comes from passenger fees. The rest comes from local, state and federal governments. (New York City actually takes some toll revenues from its automobile bridges and tunnels and uses the money to help pay for its bus and subway system.)
"In the U.S., as is many other parts of the world, public transportation is subsided by local, state and national governments," said John Collura, a transportation professor at the University of Massachusetts-Amherst. "It could be in the order of 60, 70, sometimes 80 percent. A lot of people go to Europe and other parts of the world and they come back and ask why we don't have such great public transit systems."
The reason: European governments have chosen to heavily subsidize city subway systems and inter-city rail lines. America has not.
"If you tried to operate without subsidies, the fares would be excessive," Collura said, noting that "you and I who may use our automobile, don't pay the full costs associated with using it."
The government builds bridges and highways for cars. Not to mention the street signs, traffic lights, painting the roads and filling in potholes.
But, ultimately, for the millions of Americans who live in rural areas, such transit options are simply unfeasible.
"I think it's absolutely a viable solution for many people but not all," Collura said. "In many areas, services don't exist because it's so expensive to provide them. It's very difficult to justify them in a low-density area."