Valtteri Bottas says Williams still has room for improvement despite a solid first day at the wheel of the new FW35.

The young Finn took over from Pastor Maldonado on Wednesday for his maiden run in the new car, which was only launched in Barcelona prior to the second pre-season test of the year getting underway.

Completing just shy of 100 laps, Bottas posted the sixth quickest time and said it was clear to see that the new car is a step forwards from the one it replaces.

"I had a really strong first impression of the FW35 today," he said. "Once we completed the aero work this morning I was able to complete my first proper run to feel the FW35 and the improvements we have made. Straight out of the box I knew we had made a step forward from last year, and I am looking forward to working to develop the car even further.

"It's great to know we have a really good base to start from but there are still a number of areas we can improve, so I'm really excited for the season ahead."

Technical director Mike Coughlan was also pleased with another solid run for the new car on only its second day on track.

"It was a trouble-free day for us with Valtteri completing close to 100 laps, so we are pleased with the reliability of the FW35," he said. "Valtteri confirmed the potential of the car posting some competitive times throughout the day. After initially concentrating on aero testing, our focus then switched to set-up work and the tyres this afternoon.

"We are pleased with the progress we are making as a team and we have a good direction to continuing developing the car ahead of the season."

Bottas will share track time with team-mate Pastor Maldonado on day three.