Robert Kubica: Polish driver has 'productive' second Williams test

Robert Kubica has completed a second day of testing for Williams as the team assess the chances of the Pole making a comeback to Formula 1 in 2018.

Kubica, 32, has not raced in F1 since suffering a partially severed right arm in a rally crash in 2011, external but is in the running for a Williams seat next year.

Williams said Tuesday's test at the Hungaroring was "productive". Kubica also tested at Silverstone last week.

Williams reserve driver Paul Di Resta will test on Wednesday as a benchmark.

"We will not release any further information regarding the tests as we continue our evaluations," the team added.

Kubica, who still has only partial movement in his right arm after more than six years' rehabilitation, is essentially up against Williams' current driver Felipe Massa for a seat next year alongside Canadian Lance Stroll.

Di Resta, 31, has an outside chance but is not considered a serious candidate at this stage, the team feeling reserve driver is the ideal role for the Scot who subbed for Massa at the last minute when the Brazilian was taken ill at this year's Hungarian Grand Prix.

Kubica conducted three tests for Renault this summer, the final one in a 2017 car at the Hungaroring in early August.

The French outfit, which was Kubica's last F1 team in 2010, ultimately decided against pursuing their interest in their former driver, preferring instead to sign Carlos Sainz on loan from Red Bull for 2018.

The Spaniard, 23, begins his Renault career at this weekend's US Grand Prix, after Briton Jolyon Palmer was dropped following the last race in Japan.

Sainz's former team Toro Rosso are fielding their former driver Daniil Kvyat and Porsche endurance racer Brendon Hartley at the event in Austin, Texas.

Toro Rosso needed to draft in New Zealander Hartley, a former Red Bull junior who was dropped from the programme in 2010, because Frenchman Pierre Gasly is racing in the final round of the Japanese Super Formula championship, which he has a chance to win.

Kvyat was dropped in favour of Gasly after this year's Singapore Grand Prix because of poor form.

It is unclear whether Kvyat, from Russia, or Hartley will retain their drive when Gasly returns for the final three races of the year in Mexico, Brazil and Abu Dhabi.