A bicycling advocacy group is trying to convince the MTA to catch up with the rest of the country by expanding bike parking to inside subway stations.

Transportation Alternatives, the advocacy group, has already discussed its suggestion for in-station racks with the Metropolitan Transportation Authority.

"It's something the MTA could do easily and cheaply with space they already have," said Caroline Samponaro, a project coordinator at Transportation Alternatives.

But the MTA is not giving the idea a green light.

"For a variety of operating and security concerns, we are not to my knowledge considering allowing customers to park and lock their bicycles in stations," Transit Authority spokesman Paul Fleuranges wrote in an e-mail yesterday. "I have been told that we are working with DOT to explore providing bicycle parking outside of select stations."

Expanding bike access and ridership has been part of Mayor Michael Bloomberg's goal for reducing congestion and carbon emissions. The city Department of Transportation, which installed 800 bike racks during 2007, has begun to put up covered bike rack shelters outside transit stations, including at Union Square and DeKalb Avenue.

Around the country, systems like Chicago's El and San Francisco's BART are already allowing racks inside. Chicago has a handful of bike spaces in more than 80 stations.

"Having the bike inside the facility lends a slightly higher level of protection from theft and vandalism," said Brian Steele, a spokesman for Chicago's Department of Transportation.

Several cities around the country offer more than the basic rack at the subway station. Lockers and even valet service are also being used. Chicago and San Francisco already have valet services that handle hundreds of bikes, and next year, Washington, D.C., will also join the group. The locations are often public-private partnerships that give a bicycle retail and repair business store space at a transit stop in return for parking the bikes and watching over them.

Transportation Alternatives has suggested valet bike stations at major subway hubs like Grand Central, the Fulton Street Transit Center in Lower Manhattan, Atlantic Avenue in Brooklyn, and Queens Plaza. A spokesman for the city DOT said the agency is considering the idea but had no immediate plans to put a bike station into operation.