Track workers have laboured through the night to make changes to the Baku street circuit for the European Grand Prix after problems with kerb plates lifting in practice.
Race director Charlie Whiting told Reuters on Saturday the white lines marking the pit lane entry and exit had also been repainted to improve safety.
“Just the lines, that’s all, to keep the drivers slightly further left so that there’s no misunderstanding if two cars are following and the front one wants to come in,” he said.
“The idea is that it should be slightly clearer to the driver behind that the car is coming in to the pits.”
Some Formula One drivers had expressed concern about the pit lane approach, which enters a chicane after leaving the long main straight and then continues before reaching the point where the speed limiter comes into force.
Whiting said there had been no change in the point at which drivers had to slow.
The kerb plates, which are bolted to concrete inserts into the bitumen, were removed at turns six and 12 and replaced by painted areas that looked like kerbs.
“We decided to do that rather than try and monitor the kerbs,” said Whiting, adding the fixings were the same type that Formula One had used without problem in Mexico and Singapore.
“It’s a little surprising to see that they are coming up here,” he said.
“There’s clearly something different. We’ve still got them in a couple of other corners which we don’t anticipate any problems with.”
Mercedes triple world champion Lewis Hamilton set the pace in practice on Friday, lapping in one minute 46.435 seconds in the first session and later improving that to 1:44.223.
The Briton is now only nine points adrift of teammate and championship leader Nico Rosberg after seven of 21 rounds.
Rosberg was second in both sessions, and ended the day early after stopping on track following a loss of power with about 20 minutes remaining.
Australian Daniel Ricciardo brought out the red flags to halt the first session with 22 minutes remaining after he clouted a barrier, with the impact ripping off his Red Bull’s rear right wheel.
After a third practice round, qualifying starts from 5pm (2200 AEST) on Saturday, and the race is from 5pm on Sunday.