SILVERSTONE, Great Britain -- After testing the latest version of the Halo, Sebastian Vettel has raised fresh concerns over the restrictions the head protection system places on visibility.

Ferrari tested Halo 2 during free practice for the British Grand Prix, which features a stronger, lighter design with a narrower supporting strut in front of the cockpit. Vettel is the first driver to test the latest iteration of the Halo, which the FIA is keen to get signed off this month in order for it to be introduced next year, but his first impression was not entirely positive.

"Not great," he said when asked about the test. "There is quite a bit of impact in terms of visibility. But it was just a standard check."

After testing the first version of the Halo this year, Vettel said "you can see what you need to see" and teammate Kimi Raikkonen reported "there was surprisingly little difference" to running a completely open cockpit. It remains to be seen whether Vettel's latest comments result in either changes or a delays to the design.

Speaking about Ferrari's performance in practice after finishing the session over 0.9s off Lewis Hamilton's Mercedes, Vettel added: "I think it was a bit mixed. It was quite windy, the beginning was not so good but I think the long run was OK.

"We need to do quite a lot of work to improve the car but we have a baseline and today we understood and learned quite a lot."