Q: Several times while trying to drive over the Queensboro Bridge, I’ve been caught on this roadway that seems to hang off the side of the bridge. What is it, and was it a part of the bridge’s original design?

A: The outer roadway on the southern side of the lower level of the Queensboro Bridge (also known, as in the Simon and Garfunkel song “Feeling Groovy,” as the 59th Street Bridge) may well be one of the city’s scariest places to drive. The motorist must navigate an eerily straight yet unforgivingly narrow roadway that hangs more than 300 feet above the East River.

The roadways – the northern one is now dedicated mostly to pedestrians and cyclists- are so straight because they were used by trolleys after the bridge opened on June 18, 1909. The trolleys, operated by Queensborough Bridge Railway, stopped along the 7,449-foot bridge at four stations: one at each end, one above Vernon Boulevard at Long Island City, and one above Roosevelt Island.

Large freight elevators provided service between the ground and stations on the bridge at the two middle stops. Besides carrying passengers, the elevators allowed ambulances and trucks access to Roosevelt Island – which when the bridge was built was called Blackwell’s Island, and later Welfare Island.

In 1957, three years after the construction of the bridge connecting the island to Queens, it was decided the trolleys were no longer necessary. Service gradually ceased, and the tracks were converted into the roadways you see today. The elevators, however, were not removed until 1970. The kiosk on the Manhattan side is still visible on Second Avenue.

I noticed that the Astor Place station is decorated with beavers, which seem an odd choice for a subway stop. What is their significance? Are they a reference to the subway burrowing?

If any rodent were to represent the subway system, we know which one it would be. You do bring up an important historical footnote. Astor Place got its name from the Astors, the prominent 19th-century family. John Jacob Astor, a German immigrant, made much of his early money in the Midwestern and Canadian fur trade. As a result, the beaver came to be synonymous with the entire Astor family, even after they left the fur trade for the ritzier real estate scene. Beyond Astor Place, another New York locale named for the family is Astoria.