Favour 'halo' head protection device: Felipe Massa
A Ferrari spokesman said the version tested was a provisional structure to test lines of sight.
A prototype "halo" head protection device made its Formula One test debut in Spain on Thursday, with Kimi Raikkonen declaring visibility to be "okay" after lapping with it attached to the cockpit of his Ferrari.
The governing FIA has said a version of the device, which is fixed to the cockpit at three points including a central pillar right in front of the driver, could be introduced next year.
A Ferrari spokesman said the version tested was a provisional structure to test lines of sight, with Raikkonen completing two laps. "Kimi said it was 'okay' in terms of visibility," he added.
Most drivers favour the device, designed to protect against potentially lethal flying debris, although some have reservations about how quickly they could get out in an accident.\
Halo device important for safety: Felipe Massa
"It’s important for safety and I am totally in favour. I think we need that," Williams driver Felipe Massa, who suffered a near-fatal head injury while driving for Ferrari in Hungary in 2009, told Reuters last week.
"It doesn't look good but it's for a great reason," McLaren's Jenson Button told Sky Sports television at Barcelona's Circuit de Catalunya.
"I'm not sure how we are going to get out in 5 seconds but I think it's something that is needed in the sport."
Mercedes driver Nico Rosberg said it was potentially a "massive step in safety".
"I think it's definitely needed. OK, visually you can say that it's not quite as good as now but from some angles ... it looked very cool actually," said the German.
Red Bull principal Christian Horner, whose team are planning to test a different version next month, said it was good that teams were trying it out but had reservations.
"We've tried it on our simulator," he said. "We're concerned with some visibility issues on it.
"Personally I'm not a fan of that system, I think we can do better than that with something a bit more elegant rather than a big piece of carbon fibre right in front of the driver's face."
Driver safety important for Formula One
Formula One has been weighing up the pros and cons of the halo compared with completely closed canopies, an option that some fear could trap the driver in the event of a crash.
Improving head protection became a priority after the deaths last year of Briton Justin Wilson, a former F1 racer who suffered head injuries from debris in an IndyCar crash, and Frenchman Jules Bianchi.
Bianchi, Formula One's first driver fatality in 21 years, died in July, nine months after suffering severe head injuries at the 2014 Japanese Grand Prix when his car hit a recovery tractor.