Alexander Rossi has edged Andretti Autosport team-mate Colton Herta to top spot in IndyCar Practice 1 at Road America.

Rossi’s pace-setting 1:45.6027s was 0.1334s than Herta’s personal-best, with Chip Ganassi Racing’s Marcus Ericsson taking third in another Honda-powered car.

Team Penske’s Will Power was first of the Chevrolet contingent in fourth, with Alex Palou (Ganassi) fifth, from Scott McLaughlin (Penske) and Scott Dixon (Ganassi).

The very fastest times of the longer than usual, 75-minute session were set on the alternate tyres, given each driver is now compelled to hand back one set of the reds, but Rossi was fastest on blacks also.

Due to the length of first practice, it was a quiet opening before Devlin DeFrancesco (Andretti Steinbrenner Autosport) set a remotely representative lap time, a 1:49.3642s, which he backed up with a 1:47.9578s next time through.

Beyond the 20-minute mark, Callum Ilott (Juncos Hollinger Racing) set back-to-back 1:47.7437s and 1:47.6760s laps on his return to competition after a hand injury forced him out of the Detroit event, then Romain Grosjean (Andretti) clocked a 1:46.9302s as the heavy-hitters started to roll out.

In Simona De Silvestro’s first event of the season, Paretta Autosport had to attend to a not especially unusual brake fire on the left rear of the #16 Chevrolet, while Rossi (Andretti) shifted the benchmark to a 1:46.6714s just past half an hour in.

First of the notables to show their hand on reds was Grosjean, but he improved only ever so slightly from that earlier 1:46.9302s to a 1:46.9190s at the time.

Shortly after, Helio Castroneves (Meyer Shank Racing) triggered a red flag when he arrived too hot at Canada Corner (Turn 12), spun, and came to rest on the grass in the 56th minute.

At that point, it was Rossi, Herta (Andretti w/ Curb-Agajanian), Ericsson, Grosjean, and Power on a 1:46.9630s filling the top five, four of whom had only run blacks.

The green flag came after a halt of around five minutes, leading to a flurry of faster laps due to a broad switch to red tyres.

Josef Newgarden (Team Penske) set a 1:46.1714s with just over 10 minutes remaining, then Rossi a 1:46.0861s, and, suggesting the alternates would need multiple laps to come up, Newgarden a 1:46.0594s on his next lap.

Herta was first into the 45s when he punched out a 1:45.7361s, which Rossi knocked off with a 1:45.6027s as he too went quicker on consecutive laps.

No one would do better than that, although Ericsson took up third with a subsequent 1:45.8050s, from series leader and last-start winner Power on a 1:45.8592s, and Palou on a 1:45.9140s.

McLaughlin had an innocuous, final-corner off earlier in the session before setting a 1:45.9316s which was good enough for sixth, ahead of Dixon on a 1:46.0494s.

Rounding out the top 10 were Newgarden, Simon Pagenaud (MSR), and Pato O’Ward (McLaren SP), while De Silvestro ended up last of the 27 drivers on a 1:48.7490s.

Practice 2 starts on Sunday at 00:45 AEST, ahead of Qualifying from 03:45 AEST, with both of those sessions live and ad-free on Stan Sport.

Results: Practice 1