ROAD RAGE bubbled as the track temperature rose in the second practice session for United States Grand Prix on Friday as Max Verstappen called title rival Lewis Hamilton a “stupid idiot”.

World champion Hamilton angered Verstappen by pushing past on the inside of the Red Bull when the Dutchman was lining up a flying lap.

Verstappen leads Hamilton by six points in the title race.

After the Mercedes almost pushed Verstappen off the track, the Dutchman gave way, lifting his right hand off the wheel to make a gesture with his middle finger at the rear end of Hamilton’s car.

Verstappen complained on team radio that Hamilton was a “stupid idiot” and never seemed to recover his poise, ending the session eighth fastest.

His team principal Christian Horner was calmer.

“They were obviously queing up to start the lap and Lewis decided just to jump Max there,” Horner told UK Sky TV from the pit lane.

“They have an unwritten rule in sessions like this that they take their turns and Max was pointing out that he was first in the queue.”

Verstappen never found a gap in traffic to make another attempt.

“Why do we always go in traffic. Jesus,” was part of a later radio message that also contained several swear words.

He was not the only angry driver.

Nikita Mazepin was almost sideswiped by a driver exiting the pits.

“What was that man? Just avoided a crash,” said the Russian. “Man it’s impossible to get a lap on this track.”

After the session, with his helmet off but his mask on, Verstappen was more guarded.

“Just a mess with the traffic,” he said before addressing the Hamilton incident in a bewildered tone.

“We’re all lining up to go for our laps so I don’t really understand what happened there.”

Yet the afternoon was not a total loss for his team, which had been badly outpaced by Mercedes in the morning.

Red Bull’s Mexican driver Sergio Perez was fastest with a time of 1min 34.946sec.

Lando Norris of McLaren was second 0.257sec behind.

Hamilton who had what would have been the fastest time of the session scrubbed out because he crossed the white track limits line on trun 19, was third 0.364, 0.50sec ahead of teammate Valtteri Bottas.

Daniel Ricciardo of McLaren, Lance Stroll in an Aston Martin and Ferrari’s Charles Leclerc were the next three fastest, ahead of Verstappen.

“It was a good day,” said Perez. “Obviously it’s going to be very tight trying to put it all together and find those couple of tenths that would put us in the mix for pole tomorrow.”

- ‘Hands sticking to wheel’ -

Perez said the real problem was not the heat, which reached the mid-80s Fahrenheit.

“Very humid as well,” said the Mexican. “My hands are sticking to the wheel a lot.”

Mercedes dominated in the morning and Hamilton said changes the team made between sessions had not worked.

“We lost some ground or they gained some ground,” he said. “It’s been a good day but work to do.”

Bottas faces a grid penalty on Sunday after Mercedes changed his engine for the fifth time this season.

After Hamilton took an ultimately costly 10-place grid penalty for an engine change before the Turkish Grand Prix, Bottas and two other drivers with Mercedes power units, George Russell of Williams and Sebastian Vettel of Aston Martin, are taking penalties in Austin.

Drivers are allowed three engines a season, after that they are hit with decreasing penalties.

Bottas drops five grid places for his sixth engine. Russell and Vettel will drop to the back of the grid after each switched to their fourth power unit of the season.

“Unfortunately since mid-year we have had some reliability issues that keep coming back,” Mercedes team principal Toto Wolff told Sky.

“Penalties are not nice because it’s such a tight battle.”