How the the Kennedy assassination totally transformed presidential cars, from an open-top Lincoln Continental to the heavily-armored 'Beast' used by Trump and Obama

The vehicle that President Kennedy was riding in on the day of his assassination was a 1961 Lincoln Continental.

Its low-slung elegance was perfectly suited to the forward-looking image Kennedy sought to project.

After leasing the vehicle from Ford, the Secret Service made some adjustments, including a special phone system and a mechanism to elevate Kennedy's seat to give crowds a better view.

But the car had no armor or other protective features. Even had its bubble roof been in place that day in Dallas it would have provided no shield against the assassin's bullets.

After Kennedy's assassination, the 1961 Lincoln Continental Presidential Limousine model in which he travelled was given a substantial redesign.

According to the Henry Ford Museum of American Innovation, the vehicle was given a permanent roof, titanium armor plating, an explosion-proof fuel tank, and run-flat tyres.

At the request of Kennedy's White House successor, Lyndon Baines Johnson, the color of the car was changed from midnight blue to a more sombre black.

The next major redesign took place during the presidency of Richard Nixon, with the new model of Lincoln Continental unveiled in 1972.

Though it wasn't a convertible, the vehicle had opening roof panels if the president wanted to stand and wave to crowds from the vehicle while electioneering or on official visits. An extra quarter inch of armor was added, bringing its weight up to 5,000 pounds.

The vehicle was put to the test in two presidential assassination attempts, speeding President Gerald Ford from Union Square, San Francisco, after Sara Jane Moore narrowly missed him in a shooting in 1975.

Jimmy Carter also used the same model when he took over in 1977, as did Ronald Reagan from 1981.

That year, one of the six bullets, fired by would-be assassin John Hinckley Jr, hit the right window of the vehicle, and another ricocheted from its roof, seriously wounding the president. He later made a full recovery.

The Secret Service — which is responsonsible for the presidential car — switched to Cadillac for the vehicles used by President Reagan and his successors, George HW Bush and Bill Clinton.

Reagan's Cadillac had a slightly raised roof and seats, so the president could be seen by crowds.

But unlike the open-roof models previous presidents travelled in, this one was encased by bulletproof glass.

Clinton's 1992 Cadillac Fleetwood Brougham eschewed the running board and sunroof of the earlier model, for extra security.

George W Bush's Cadillac DeVille was the first to be specially built to the specifications of the Secret Service, and not based on a commercial model. Features added by the Secret Service to previous models added so much weight they caused malfunctions, like break failings.

With the days when presidents travelled with open roofs long gone, this sealed off vehicle had its own air supply, 5 inch armor, and Popular Mechanics reported, glass so thick "it blocked off part of the color spectrum."

It also boasted "a big 454 cubic inch truck engine so the 14,000-or-so pound monster could push through any obstacles."

Brought into service in 2009 for President Barack Obama's inauguration, the 2009 Cadillac Presidential Limousine weighs in at a massive 10 tons.

Its the kind of vehicle used by Donald Trump, the current president.

The vehicle comes with a formidable array of weapons and armory.

Its eight-inch walls and five-inch windows make the doors as heavy as those on a commercial jet, and it is sealed against biological attacks.

"It can put out a smokescreen, fire tear gas, and lay down an oil slick to send vehicles chasing it out of control. Even the door handles can be electrified to shock those who might try to get inside,"reported NBC News.

The vehicle even contains a fridge full of the blood matching the president's blood type, in case an assassination attempt puts him in need of an emergency transfusion.