Most people would accept that Formula 1 is a dangerous sport, but is it really as treacherous as the new adrenaline-fuelled racing biopic Rush makes out?

The film, which charts the rivalry between British playboy driver James Hunt and Austrian World Champion Niki Lauda, makes a number of claims about the high-risk world of F1.

"I accept every time I get in my car there's 20% chance I could die," declares actor Daniel Bruhl, who plays Niki Lauda in the film.

"What kind of person does a job like this?" he asks. "Each year two of us die."

Let's take each of those in turn. First the claim that drivers had a 20% chance of dying in every race - a statement that has been accepted as factually accurate by several reviewers.

Roger Smith, racing fan and author of Formula 1: All The Races suggests some "dramatic licence" has been employed here.

Drivers killed in F1 in 60s and 70s Chris Bristow (UK) and Alan Stacey (UK) Belgian GP, 19/6/60

(UK) and (UK) Belgian GP, 19/6/60 W von Trips (Germany) Italian GP, 10/9/61

(Germany) Italian GP, 10/9/61 C G de Beaufort (NL) German GP, 2/8/64

(NL) German GP, 2/8/64 John Taylor (UK) German GP, 7/8/66

(UK) German GP, 7/8/66 Lorenzo Bandini (Italy) Monaco GP, 7/5/67

(Italy) Monaco GP, 7/5/67 Jo Schessler (France) French GP, 7/7/68

(France) French GP, 7/7/68 Gerhard Mitter (Germany) German GP, 2/8/69

(Germany) German GP, 2/8/69 Piers Courage (UK) Dutch GP, 7/6/70

(UK) Dutch GP, 7/6/70 Jochen Rindt (Austria) Italian GP, 5/9/70

(Austria) Italian GP, 5/9/70 Roger Williamson (UK) Dutch GP, 29/7/73

(UK) Dutch GP, 29/7/73 Francois Cevert (France) US GP, 6/10/73

(France) US GP, 6/10/73 Peter Revson (USA) South African GP, 22/3/74

(USA) South African GP, 22/3/74 Helmuth Koinigg (Austria) US GP, 6/10/74

(Austria) US GP, 6/10/74 Mark Donohue (USA) Austrian GP, 19/8/75

(USA) Austrian GP, 19/8/75 Tom Pryce (UK) South African GP, 5/3/77

(UK) South African GP, 5/3/77 Ronnie Peterson (Sweden) Italian GP, 10/9/78 Deaths in World Championship Grand Prix (GP) race or practice

"Certainly Formula 1 is a dangerous sport, people can die participating in it," he says.

But this particular statistic, he regards as "slightly over-egged".

Niki Lauda himself, when approached by the BBC for a comment, sent a message back saying that it was "a rhetorical statement rather than a precise statistical calculation".

So what were the real risks?

According to Kevin McConway, Professor of Applied Statistics at the Open University, in the decade leading up to 1976 - the year in which the film is set - drivers had a 0.35% chance of dying each time they competed in a Grand Prix (including any practice and qualifying sessions).

That is a lot less than 20% "every time I get in my car".

But the odds rose to 4.4% across an F1 season and higher still if a driver raced in every race for five years. At that point his chance of death did indeed approach 20%, McConway says.

To put that into context - the risk to a Formula 1 driver dying per race was equivalent to travelling 1.5 million miles by car today, or completing 500 sky dives.

What about the second claim - that each year two Formula 1 drivers died?

If only those fatalities that occurred during either a F1 World Championship race or practice are counted, then there were fewer than two deaths each year.

In total, eight drivers died in the 1960s and nine in the 1970s.

But there is another way of looking at the figures.

"When some of these claims are made about the incidence of death in Formula 1, there is a bit of a grey area as to the fact that there was a high incidence in motor sport in general," explains Roger Smith.

"Some of those Formula 1 drivers who can be listed as the death of a Grand Prix driver actually were driving other forms of motor sports…Indeed [F1 Champion] Jim Clark was killed in a Formula 2 accident in 1968."

Image caption Niki Lauda was pulled from his burning car at the Nurburgring in 1976

Counting up how many Formula 1 drivers were killed, you get much higher numbers - 29 deaths in the 1960s and 18 in the 1970s.

Racing legend Sir Jackie Stewart has said that during the years that represented the peak of his career in the late 1960s and early 70s, anyone continuously racing had a two-out-of-three chance of dying.

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And when you look at the numbers of F1 drivers who were killed (in F1 or another professional race) over five years at the height of the Jackie Stewart era, he was not that far off - they had a 50-50 chance of dying, Kevin McConway calculates.

Being a professional racing driver 40 years ago was unbelievably dangerous. There just wasn't a safety culture. Even seatbelts were not made mandatory until 1972.

That period is now behind us. No Formula 1 driver has died since Ayrton Senna in 1994, though some race marshals have been killed.

After Senna was killed "it was recognised that safety had to be probably the number one on the F1 agenda, above the show, the entertainment value and everything else," says Roger Smith.

"In the 50s there wasn't a safety culture. It was just after the Second World War - people were used to the idea that people could die and I think that people found it almost acceptable."

Image caption James Hunt on his way to becoming 1976 World Champion, with a third-place finish at the Japanese Grand Prix

For one thing, there has been a switch to shorter race tracks.

"Tracks could be up 15 miles long. The Nurburgring was that sort of length and getting safety cars to support the drivers in the event of an accident…was almost impossible," Smith says.

"So, road circuits of that type gradually disappeared. The last time that the Nurburgring was used was that 1976 race where Niki Lauda was so badly injured."

Conditions for today's Formula 1 drivers are, thankfully, much safer.

Technology has also transformed cars beyond recognition.

Formula 1's turnaround since 1994 is "amazing record" says Roger Smith, but he insists that the sport can never afford to stop working at it.