NYSE, which announced the change on Wednesday, restricts floor trading to the 3,166 stocks listed on the Big Board. The action will raise the number of securities that can be traded through a floor broker to 8,600 and includes stocks and ETFs from all-electronic markets Nasdaq Inc (>> Nasdaq Inc), Bats Global Markets (>> Bats Global Markets Inc) and NYSE Arca.

Over the past several decades as stock trading has become more electronic, most trading floors have been closed in favor of fully automated exchanges, many of which emphasize speed and allocate stocks based on a first-come first-served model at the best price available.

Critics say the focus on speed has created an unlevel playing field where firms using high-frequency trading strategies can use sophisticated technology to gain an advantage over investors with less means.

The floor trading model used by NYSE, a unit of Intercontinental Exchange Inc (>> Intercontinental Exchange Inc), gives multiple investors access to trade at the same price, regardless of when their orders were placed, making speed less important.

"Our plan to provide even greater access to trade U.S securities is a positive move toward bolstering fair and transparent liquidity and offering even greater choice,” Stacey Cunningham, chief operating officer of NYSE, said in a statement.

NYSE is in the middle of moving its equities and options markets, including the NYSE, NYSE MKT, NYSE Arca Equities, NYSE Arca Options, and NYSE Amex Options, to a new trading technology platform, known as Pillar.

The additional securities will be made available for floor trading on the NYSE by year-end, once the new technology is in place.

(Editing by Steve Orlofsky)