Residents of Roosevelt Island and their elected officials are pushing forward a plan to build a staircase and elevator that would connect the East River isle to the Queensboro Bridge.

Connecting the two-mile strip of land to the walkway on the lower level of Queensboro Bridge, the staircase and elevator would provide residents with an escape route in an emergency situation, community members said.

“You can’t get off Roosevelt Island fast enough right now,” the president of the Roosevelt Island Residents Association, Matthew Katz, said. “We need to find alternative ways to get people on and off the island.”

If only the stairway were built, “it would be quite a hike” up to the bridge’s walkway, Mr. Katz said. No cost estimate for the plan has been determined.

There are island apartment towers and two hospitals on the island, but no emergency room and only a part-time fire department. Roosevelt Island was developed by the state in the 1960s as a planned community to provide affordable housing for middle-class New Yorkers in rental and co-op facilities. The community has just one street — Main Street. “You feel like you’re somewhere in Middle America here,” Mr. Katz said.

The few transportation options to Manhattan from Roosevelt Island are functioning at their peak capacity, and the island’s population is expected to grow to about 20,000 residents from 12,000 over the next few years, according to Mr. Katz.

The island is currently accessible by one stop on the F train, the Q 102 bus, the tramway, and the Roosevelt Island lift bridge to Astoria, Queens. At rush hour, island residents commuting into Manhattan often have to let four or five subways pass them by before they’re able to squeeze onboard, Mr. Katz said.

The lift bridge also often gets stuck and does not allow cars to pass to and from Roosevelt Island.

The proposed staircase and elevator would be built just south of the tramway station on the island, near the tennis bubble. The Queensboro Bridge, which stretches to midtown Manhattan from Queens, has an anchorage on Roosevelt Island that could be used to support the stairway, Mr. Katz said.

“I think it’s a great idea to provide direct access from the bridge to the island,” Council Member Jessica Lappin, who represents Roosevelt Island, said. “A stairway seems like a reasonable, low-cost way to provide that access.” Ms. Lappin said she has already requested that the Department of Transportation pursue the plan, but that her appeal was shot down.

A spokeswoman for the Department of Transportation, Kay Sarlin, said yesterday that the department opposed the proposal. “The installation of an elevator would require the removal of one lane of traffic from one of the busiest bridges in New York City,” Ms. Sarlin said in a statement. “Due to the limited capacity of an elevator as well as other issues with security, maintenance, access, landmarks status of the bridge, and costs, an elevator is not an option.”

The transportation department would not build a stairway without an elevator because it would be inaccessible to people with disabilities.

The Roosevelt Island Residents Association plans to discuss the proposal at a Community Board 8 meeting Tuesday evening.