Formula One team bosses have warned that rookies are unlikely to see more track time next year despite the longer FP1 sessions.
All teams have agreed to extend Friday's first practice from 90 minutes to two hours with the aim to give test drivers an opportunity to get more mileage under their belts.
Youngsters will be allowed to run during the sessions, but they can be replaced by regular drivers at any time while teams will be given an extra set of tyres that can only be used during the first 30 minutes of FP1.
However, Mercedes team boss Ross Brawn has warned that his squad are likely to give their race drivers more time behind the wheel during the longer session.
"I think for us we'll still stick with race drivers," Brawn is quoted as saying by ESPNF1. "One of the main changes is an extra set of tyres for the first half hour, which I think is a good move, and the ability to change drivers during a session, which is actually not easy.
"If you've got drivers with too much variance then it's not such an easy thing but it's doable. But it's not something that we would be considering because we need all the time in the car with our two race drivers - all the time we can get in the car with them - so I think there will be a point on the grid where it is more attractive to some teams, but certainly not for teams that are fighting for races and fighting for Championships."
Meanwhile his McLaren counterpart Martin Whitmarsh believes the rule change could be bad news for the smaller teams on the grid.
"I think from McLaren's perspective it's not something that we'd necessarily want to do," he said. "I can understand the view of some - which is that it's very difficult for young drivers, there's very little testing and it's a way of encouraging them - but oddly I think it will work against the smaller teams because at the moment they have a unique opportunity to sell FP1; many do and it's a surprisingly important revenue for some of those teams.
"If every team has that opportunity then the value of what some of those smaller teams are able to sell is reduced. So oddly I think it would probably work against them. I think that you'd probably end up if it was forced - because none of the big teams would do it unless the regulations actually prescribed and required you to have a young driver or whatever the definition - frankly from our perspective you'd go to work thinking how can you use that half an hour to do aerodynamic testing.
"We would ultimately not do effectively performance testing in terms of lap time, set-up, we'd be doing a whole range of component changes and just data logging on the straights I expect. So it probably wouldn't have the desired effect, although you'd have to look at the precise detail of what they define. As is often the case, quick ideas in Formula One have unintended consequences and the teams figure it out for themselves how to exploit it to their best advantage, not necessarily aligned with the original intention of such an idea, so I think you'd have to think about it carefully."
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