Max Verstappen and Lance Stroll escaped punishment following an investigation into a crash during practice at the Portuguese Grand Prix.
The pair collided as Verstappen tried to overtake Stroll after they had raced down the pit straight.
Stewards called both drivers to give evidence and ruled that neither was "wholly or predominantly at fault".
Mercedes' Valtteri Bottas was fastest overall in the session from Verstappen, with Lewis Hamilton eighth.
Red Bull's Verstappen swore over the radio immediately after the crash between the two drivers, asking what Stroll, of Racing Point, thought he was doing.
Stroll had passed Verstappen at the final corner of the previous lap. Verstappen attempted to pass back at the start of the next lap, but Stroll turned in.
The stewards' report said: "Stroll was on a fast lap and was allowed to pass by Verstappen on the lap preceding the incident.
"Given the information from his team and usual practice, Verstappen assumed that Stroll would back off for the next lap and moved to overtake along the main straight.
"However, Stroll was instructed by his team to go for a second flying lap. Stroll assumed that Verstappen would have backed off to gain a gap between them, also in line with usual practice, and so was not looking for the overtaking Verstappen.
"The drivers agreed in the hearing that the incident was the result of a misunderstanding between them and that with hindsight, both could have contributed to avoid the incident."
The incident led to one of two red flags in a disrupted session that left teams and drivers with little information on a track that is new to F1.
The first stopped was caused when Pierre Gasly's Alpha Tauri caught fire.
A mandatory Pirelli tyre test on development tyres for 2021 run in the first half-hour of the session further limited useful running and meant the session was unrepresentative of the true competitive order.
Gasly's problem interrupted Hamilton's quick lap on the soft tyres, while Bottas managed to complete his before the session was stopped.
Hamilton did manage to get in another lap before the second red flag, but was 1.3 seconds off the pace.
Bottas had earlier topped the first session, 0.339secs ahead of Hamilton, with Verstappen third.
McLaren's Lando Norris was third fastest, from Ferrari's Charles Leclerc and their team-mates Carlos Sainz and Sebastian Vettel.
Ferrari have the latest in a series of aerodynamic upgrades, some developments on their floor being introduced in Portugal following changes to the front of the car at the last two races.
Hamilton, who will break Michael Schumacher's all-time record of victories if he wins on Sunday said he had enjoyed the Autodromo do Algarve but had had a troubled day.
"Incredibly difficult circuit," the world champion said. "Massively challenging. The undulations are incredible
"A lot of places you can't see where you're going - exit of Turn Eight you are looking at the sky for a period of time, also into (Turn) 11 you turn in and you don't know where you are.
"The surface is very smooth and you see a lot of people sliding and spinning, not an easy day.
"First practice was probably the better session for me even though the car didn't feel that great and then we made some changes and it was pretty terrible in P2.
"I need to take a few steps back and see where we went wrong with the set-up."
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