Nobuharu Matsushita and Nikita Mazepin escaped serious injury after a huge crash red-flagged the Sochi sprint race in Formula 2.
Both drivers were taken to hospital for precautionary checks after the opening-lap collision.
Mazepin had started from pole, with Matsushita third, but the Russian ran wide at Turn 2 and made contact with the car of Jack Aitken, which sent him skidding back across the track and into the path of Matsushita.
The Japanese driver's car was shunted heavily into the barriers at the entry of Turn 3 and took another impact from Mazepin's car.
The red-flag period lasted more than half an hour as both drivers' condition was assessed and track repairs were carried out.
The incident is likely to bring the issue of safety back into the spotlight, with tarmac run-off areas having contributed to a number of serious incidents in Formula 1's junior series this year.
The fatal crash between Anthoine Hubert and Juan Manuel Correa was played out on tarmac run-off, although the myriad circumstances of that incident make pinning blame on one factor difficult.
Alex Peroni suffered season-ending injuries the following week at Monza, having kept his foot in after running wide at the Parabolica, only to be launched into the air by a sausage kerb, landing on the barriers, cockpit-down.
Critics say that the asphalt run-offs do not force drivers to slow down enough, making the chances of big incidents greater when drivers have lost control of their cars.
Gravel and grass have been widely favoured, with drivers more likely to be put off running wide, although both have safety concerns related to them.
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