Romain Grosjean fears F1's new standing start rule which comes into force this year could be a source of big trouble for drivers following trials of the procedure in Barcelona.
Formula 1 has amended its sporting rules for 2018 and introduced the possibility of restarting a red-flagged race with a standing start if conditions warrant the option which will be decided by F1 race director Charlie Whiting.
The system was put to the test at the end of Tuesday and Wednesday's sessions, with several drivers, including Grosjean, lined up on a dummy grid and taking part in the new procedure.
The Haas driver was unimpressed with the outcome of the trials, underlining the difficulty in launching his car off the grid on stone cold tyres.
"I didn't go above fourth gear," explained the Frenchman.
"It's undriveable. I was one of the first guys to come on the grid so I sat there with [Valtteri] Bottas for a long time.
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"But when we restarted, it was like it was raining on slicks. Every time you upshift, the rears spin and wheelspin. Every time you downshift, the rears lock. You go into a corner and slide. It's doesn't work.
"Safety-wise, I'm a bit concerned because as I say, I went to fourth gear and that was the maximum I could do.
"To me it could be carnage. You can lose the car in a straight line, and if someone loses it and then people are behind...
"We tried it, and honestly I was not having much fun just trying to upshift and downshift, it was tricky. Bottas was in front of me, and he was not having much fun either.
"I don't know what pace we've done, but look at the sector. It's going to be very, very slow."
While the relatively cold conditions in Barcelona likely complicated the standing start exercise, Grosjean believes that even in perfect conditions, drivers will struggle to bring their tyres up to the right temperature.
"It's pretty cold, but we know that if you spin and then you restart and you try to push again, the tyre's normally gone and you never put the temperature back in," Grosjean said.
"So imagine doing a slow lap and then aborting and then another one. We were down in 40 degrees or something like that with tyres. They just don't work.
"At Monaco you need 20 laps, and I'm not even sure you're going to get the temperature back. Some tracks it's fine where you manage to generate temperature.
"In Canada, or here with these conditions, China, not sure you're going to get temps again."
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