Juan Montoya ensured that Williams-BMW became the third team in four days to head the timesheets at the Circuit de Catalunya, as a reduced field took the latest Formula One group test into its fourth day.

After Jenson Button and Takuma Sato had opened the test in fine style for BAR, and Fernando Alonso picked up the baton for Renault, Montoya added his team to the list of pacesetters when he completed Thursday's sessions with a best lap of 1min 14.815secs. Although he was fully one second adrift of Sato's record pace from Tuesday - a time set on low fuel - Montoya made the most of continuing favourable weather to take his FW26 through 51 laps of aerodynamic and mechanical set-ups.

The day, which proved to be an all-Michelin affair following the departure of both Ferrari and Sauber - was dominated by Williams and Renault, with the two teams alternating places in the top four, and Nelson Piquet Jr only just missing out on fifth fastest time.

Fernando Alonso was second best on the day for the regie, lapping just over a tenth off Montoya's pace as he conducted set-up work on the new R24. The Spaniard worked through a range of spring and downforce levels during the day, as well as checking the effect of different tyre constructions on the balance of the car.

Montagny conducted set-up work with the R23, concentrating on ways of maximising the performance of the 2004 specification tyres.

Antonio Pizzonia, keen to win back his role as Williams-BMW test driver, was also out in one of the new FW26s, and clocked the third best lap as he carried out tyre evaluations with Michelin. The Brazilian completed 50 laps, setting a best time of 1:15.101secs.

Franck Montagny continued his programme in the older Renault R23, making longer runs on different tyre compounds, but still racking up the fourth best mark of the session.

Piquet Jr continued to familiarise himself with an F1 car, as well as the circuit, as he worked on set-up evaluations on last year's FW25.

Cristiano da Matta was the man to prevent Williams and Renault from sweeping the top five places on the day, and his effort was all the more remarkable as Toyota team-mate Olivier Panis suffered a heavy impact early in the afternoon session.

The Frenchman went off backwards at turn three, striking the tyre barrier with the rear of his car and taking his time to get out of the cockpit. Although he was able to extricate himself, the veteran later complained of headaches and vision problems, and the circuit medical team suggested he, like Sauber's Felipe Massa the day before, head for the local hospital for further precautionary checks.

Whilst Toyota set about investigating possible causes for the accident, however, it allowed da Matta to continue running, and the Brazilian racked up a session-high 97 laps as he worked through the development programme laid out for the new TF104.

McLaren continued in its unaccustomed place towards the rear of the field, with Alex Wurz joining David Coulthard to continue work on the MP4-19. The Scot was only 0.006secs quicker than Panis over the course of the day, while Wurz clocked the only fastest lap over 1min 16secs in the course of his 65 laps.

Leading performances (5 February) - Barcelona:

Juan Montoya Williams-BMW 1min 14.815secs 51 laps*Fernando Alonso Renault-Renault 1min 15.088secs 75 laps*Antonio Pizzonia Williams-BMW 1min 15.101secs 50 laps*Franck Montagny Renault-Renault 1min 15.156secs 77 lapsCristiano da Matta Toyota-Toyota 1min 15.718secs 97 laps*Nelson Piquet Jr Williams-BMW 1min 15.826secs 51 lapsDavid Coulthard McLaren-Mercedes 1min 15.912secs 51 laps*Olivier Panis Toyota-Toyota 1min 15.918secs 39 laps*Alex Wurz McLaren-Mercedes 1min 16.009secs 65 laps*

[all runners on Michelin tyres; * denotes 2003 car]

Weather / track conditions: Sunny

All times unofficial

Comparative lap times:

Spanish GP 2003*:

Fastest lap: Rubens Barrichello Ferrari 1min 20.143secsPole position: Michael Schumacher Ferrari 1min 17.762secs

* Note that track has been altered since 2003 grand prix.