"A car that is far more driveable, a car that you can work with from a driving point of view, you can control your management of tyre, you can control the balance and pace, was definitely not a description we could have given about last year's car," Lowe said.
"So that is very encouraging."
Williams scored just seven points from 21 races last year in one of their worst ever campaigns and travel to Melbourne for the opening race on March 17 with plenty of work to do.
Lowe hoped the team would now have a car that performed as expected.
"Something where you turn into a corner and you know what's going to happen because it happened last time," he said. "This is one of the key aspects that has been improved very considerably."