Sauber Formula 1 driver Adrian Sutil has suggested worsening visibility may have contributed to Jules Bianchi's accident in the Japanese Grand Prix.
Bianchi suffered a severe head injury after crashing into a crane while it retrieved Sutil's Sauber, which had already gone off at Turn 7 and hit the barriers in the closing stages of Sunday's Suzuka F1 race.
Sutil, who was standing at the scene when Bianchi went off, said the fading light made it difficult to spot patches of standing water on the track as the rain worsened late in the race.
"It was quite difficult. In the end we got more rain and it was dark, so visibility was getting less and less and this corner was a tricky one the whole way through," Sutil said.
"In the end, when it got dark, you couldn't see where the wet patches were and that is why I lost the car and it really surprised me.
"It [Bianchi's crash] was the same as what happened to me - he had aquaplaning but just one lap later."
Williams performance chief Rob Smedley said the light at the end of the race was worse than at any grand prix he could recall.
"It was certainly very dark at the end," Smedley said.
"I would say in the 15 years I've been involved in Formula 1 races that was the darkest I've ever seen a race event.
"I have to say I was happy when the safety car came out.
"I didn't quite understand what the reason was at that point with what was going on, but I was happy that it came out so everybody could slow down."