Toto Wolff has criticised Halo in the wake of Nico Hulkenberg's rollover crash in Abu Dhabi.
Renault driver Hulkenberg was not able to immediately escape from his car during the 2018 finale, exclaiming on the radio: "Get me out of here, there's fire!"
"I could not get out by myself," the German told reporters afterwards. "On the right was the wall, on the left was the Halo."
The FIA's Charlie Whiting defended the Halo, but Mercedes team boss Wolff insists the Hulkenberg crash is a concern.
"What worries me is that he did not get out of the car even when he saw the flames," he is quoted by Welt newspaper.
"If something really happens, then we would have to develop a system where a driver can get out of the car."
2016 world champion Nico Rosberg said a rollover crash with fire "is the only flaw, the only vulnerability, with the Halo".
"Basically the safety is much better with it, but perhaps we need to look again," he added.
