The MTA has been replacing old signals along the 7 train line for nearly a decade, and the job's still not done.

Upgrading the signals on every line so trains can run more frequently? That could take half a century.

If only some genius could find a better way.

Enter Robert James, an engineer who said installing a wireless signal system, rather than one linked by cables, could cut decades off the job.

"I think more than a genius, it's thinking outside the box and not doing things the conventional way," James said at a ceremony Friday.

He is one of eight winners of the MTA's first Genius Transit Challenge, which was created to find new approaches to reverse the sagging performance of the aging system. For their ideas, the geniuses will split $3 million in prize money.

"For too long, the MTA has been focused on maintaining yesterday's infrastructure without looking to the future," MTA Chairman Joe Lhota said. "But with this competition, we're letting all of New York know that those days are over."

Chinese manufacturer CRRC won for proposing lighter subway cars that would dramatically cut maintenance costs.

The Bechtel Company won for "The Big B," a robot that could install communication systems in the tunnels.

East Side lawyer Craig Avedisian's winning idea has a "why-didn't-I-think-of-that?" quality.

His stroke of genius? Simply adding four cars to the standard ten-car train.

"This idea, fully implemented, increases capacity in the system 42 percent," Avedisian said. "You can't even do that when you're building a subway line."

Most stations only handle ten-car trains. So how would a 14-car train work?

At one station, the doors to the first 10 cars open. At the next station, the doors to the last 10 cars open. And so on.

It's genius!

Critics questioned why the MTA, with 70,000 employees, had to look elsewhere for smarts.

"It's a very odd way to run our country's biggest transit system," said Jon Orcutt of advocacy group, Transit Center.

But the MTA said the results show that the competition was a good idea.

The MTA will now begin the process of further developing the ideas and testing them, in hopes of someday putting them into use on the subway.