In 1936, the Empire State Building was still new to the city’s skyline, cars were still a luxury good and Robert Moses solidified his legacy with the Triborough Bridge.

Nearly almost 80 years later, 432 Park Ave. reigns king in the skyline, the city is ripe with vehicles and the now-Robert F. Kennedy Memorial Bridge is one of the oldest in the city.

By the time the RFK is done with a $1.3 billion overhaul over the course of the decade, it will be the oldest and one of the most expensive city bridges maintained by the MTA. While it’s being retrofitted, redesigned and revamped to last another century, the changes don’t cover some of the changing traffic trends within the city such as pedestrian and bike paths.

“This is a huge bridge so it’s not a surprising number,” said engineering expert Sam Schwartz. “It’s a very high number, but it’s not a surprising number.”

MTA is set to pour $843 million into the RFK in the next five years for broad based overhauls such as new roads, decks, access ramps and a new toll plaza. Retrofitting for wind and seismic effects will cost the authority $163 million. The upgrade comes from a 2012 study to evaluate current and future threats to the  bridge, along with weight capacity on the bridge.

A new toll plaza and deck on the Manhattan side will cost $259 million under the proposal. While this project won’t begin until later in the plan, its intent is to replace the asphalt on the toll plaza to prevent leaking and water damage. The Manhattan plaza averaged almost 91,000 cars and trucks per day in 2012. The Bronx toll was overhauled in earlier capital plans, according to the MTA.

The price tag for all of this is high, Scwartz said, but it beats the cost and effort of building a new bridge. Reconstructing a new triborough bridge would entail land permits, lawsuits and building in heavily dense areas. A quarter of this money is likely going toward construction safety on a “live” bridge with heavy traffic.

“Building in place is very expensive,” Schwartz said. “But it’s undoubtedly far less expensive, and taking far less time than condemning property, building a new bridge, getting the property lined up.”

Bridges outside of the city have had the luxury to rebuild, such as the new Tappan Zee Bridge. While that one was designed to last only 50 years or so, Schwartz said the state has the luxury of building in a less urban area.

And the RFK’s steel and bridge design comes from an age in which bridges could last centuries. The suspension on the bridge can last longer than bridges built in the 1960s and ’70s with computer engineering that might not be as reliable, experts said. The steel in the RFK can also last another 100 to 200 years.

“Bridges built before World War II, for the most part, are stronger bridges as long as they’re properly maintained,” Schwartz said.

Investment in the RFK, which averaged more than 100,000 crossings a day in 2012, is crucial because bridges and tunnels are a major revenue driver for the MTA. That same year it raked in $336 million for the MTA, according to the city Department of Transportation. A good chunk of this in turn helps fund the subways, Long Island Railroad and Metro North.

“MTA bridges are the bread-winner for the authority,” said Adam Forman, a research associate at the Center for an Urban Future. “It’s really important that we maintain these assets.”

The MTA has not given a clear explanation of how long these upgrades are intended to last the bridge. But recent projects are the first replacements for overhauls nearly 50 years ago. Halmar International recently completed a new Queens-bound ramp in Manhattan, which replaced a ramp built in 1967.

Others have given more conservative estimates on how resilient these upgrades can be.

“You’re talking about work that will last 10, 20 years or more,” said Barry LePatner, a construction lawyer and bridge expert.

And the overhaul isn’t doing enough to address the shifting trends on how people get around. MTA officials have done little to address more bike and pedestrian traffic in the city, while the city promotes more cycle paths on bridges. A potential bike lane has been floated for the Verrazano Narrows Bridge, but nothing has yet been dedicated to it. Plans for the RFK do not include expanding bike lanes on the span, which could serve a good purpose especially between Queens and the Bronx.

Bike travel is only expected to move upward, as well. The city and Alta Bicycle Share, which controls Citi Bike, announced last week that it would double it number of bikes to 12,000 by 2017. New docks are also headed to western portions of Brooklyn and Queens.

By opening the boroughs to more bike travel, it can spur economic development and more movement between the boroughs. If a new bike path on the RFK between Randalls Island and Queens were opened, it could lead to more development in the areas like the south Bronx.

“These are really important pivot points for New York City, particularly between Queens and the Bronx, and from Brooklyn to Staten Island,” Forman said. The Queens-Randall’s Island route in its current state, he added, is “it’s particularly frightening for a biker.”

Schwartz, who would ride his bike from Brooklyn to Staten Island on the Verrazano as a teenager in the 1960s, said bike travel across MTA bridges also a unique experience: tremendous views otherwise unseen. But these views come with a price that the MTA must address before more two-wheeled vehicles have to address. In order to make bridges more bike friendly, there would have to be a way for them to slow down easier coming off the ramps.

“I’m all for retrofitting these bridges for people to be comfortable to enjoy the vistas,” he said. “Of course, you would have to figure out a way for the cyclists to slow down.”