The 76-year-old Scot, a famed safety campaigner who this month marked the 50th anniversary of his first grand prix win at Italy’s Monza circuit, told Reuters a lot more research and development needed to be done.
“One has got to be just a little careful that you don’t run too fast before all of the research has been done because there’s other types of accidents where it could be a disadvantage,” he said.
Stewart, who entered Formula One when the sport was at its deadliest and won his titles in 1969, 1971 and 1973, lost numerous friends in accidents during his career and campaigned for safety improvements including seat belts and full-face helmets.
However, he remained unconvinced by the idea of fully enclosing the driver.
“No, I don’t think so,” he said when asked whether something like that had to be done.
The world of racing has been shocked by the deaths of two top drivers in the last two months from severe head injuries sustained on the track, with increased calls for greater protection.
Frenchman Jules Bianchi, who raced for Marussia in Formula One, died in July of his injuries after slamming into a recovery tractor at the Japanese Grand Prix last October.
Britain’s Justin Wilson, who drove for the Minardi and Jaguar F1 teams in 2003, died last month after being hit on the head by flying debris and crashing heavily in an IndyCar race in Pennsylvania.
Wilson’s funeral will be held near Silverstone on Thursday, with many of his old friends from Formula One and other series set to attend.
The Briton’s death has led to a rethink about closed cockpits, with several Formula One drivers who were previously opposed now speaking out in support of measures that would offer more head protection.
McLaren’s Jenson Button, the 2009 world champion, said at Monza last week that something had to be done because ‘it’s not the 1970s…I think we’ve all had enough now.”
Stewart, who retired in 1973 after the death of Tyrrell team mate Francois Cevert at Watkins Glen in the United States, disagreed.
“I don’t see it as that bad. How many incidents have we had? I mean one thing was changing safety — the racetrack, the deformable structures, the cars, everything,” he said.
“(The death of) Henry Surtees, and this accident that happened in America, that’s two incidents. I don’t think Jules’s incident was anything to do with that (not having a closed cockpit).”
Surtees, the teenage son of 1964 world champion John, died in a Formula Two accident at Brands Hatch in 2009 when he was hit on the head by a loose wheel bouncing across the track.
IndyCar’s last fatality before Wilson was that of compatriot Dan Wheldon, the double Indy 500 winner, in a fiery crash at Las Vegas in 2011.
Formula One’s governing body has said it will carry out more tests this month on devices to protect drivers’ heads.
However previous ones have failed to overcome problems with obstructed vision and the difficulty of extracting the driver in an emergency.
“I think there’s a lot of research and development has to take place,” said Stewart. “Everyone’s talking about a missile hitting the thing. What if there’s another accident, not with a missile coming back, and an impact?
“Is it a problem that the driver might not be able to get out correctly? There’s a lot of things that you have to take into consideration.
“Are you going to get proper ventilation? It’s a very complicated thing, it’s not just a simple bubble.
“And sometimes you’ll be doing 280 or 300kph and an object comes. Is it going to damage the cell so that it can’t be taken off? A driver could be trapped in it.
“And do the spectators want it either? I think you have to be very, very certain that it’s going to work.”
(Reporting by Alan Baldwin, editing by Ken Ferris)