Among the winners sharing the $1 million prize were veteran transit companies like CSiT, which proposed software that could quickly diagnose and report train troubles, and CRRC, a giant train car manufacturer that pledged to invest $50 million to develop a new lightweight car.

One subway car idea came from an amateur transit enthusiast — Craig Avedisian, a lawyer from the Upper East Side of Manhattan, who proposed longer trains and a new passenger-loading procedure. Essentially, longer trains would mean not every car would open at every station, so passengers would have to be more attentive.

“It feels very gratifying to just be a part of the story of the subway,’’ Mr. Avedisian said Friday, at a ceremony announcing the winners at M.T.A. headquarters in Lower Manhattan. “It’s got such a long, storied history, even if I am just a footnote in that. And hopefully it ends up more than that; hopefully this will actually get implemented.”

By his own accounting, Mr. Avedisian’s plan could cost more than $17 billion. The M.T.A. said the goal of the contest was not to put exact plans into practice, but to take principles that could guide future developments.

In the signals category there were four winners dividing a $1 million pot. Two, Ansaldo STS and Thales Group, both separately submitted a proposal for a system that would use onboard sensors and cameras to position trains as a way to reduce delays.

Two other winners, Metrom Rail and Robert James, a transportation engineer, each pitched a technology called ultra-wideband wireless that can precisely locate trains, allowing more to be sent down the tracks safely. The M.T.A. has been conducting ultra-wideband testing to determine its feasibility.