The FIA has agreed to Pirelli’s request to allow the teams to do some extra tyre testing on Fridays of Grand Prix meetings.
The teams will now get their hands on four extra sets of development tyres (two per driver) of a different spec to the primes and options specified for that weekend.
Apart from anything else the change will help to ensure that the track remains busy on those Fridays, as there have been fears that cars would do limited running over the two 90 minute sessions due to lack of tyres.
The downside is that Friday’s overall times will become even harder to assess without keeping a close eye on what each driver has used, because three tyres will be in play, and quick times could be set on tyres which can’t be run for the rest of the weekend.
The FIA explained the change as follow: At certain events, one additional specification of dry weather tyre may be made available to all teams for evaluation purposes. Teams will be informed about such an additional specification at least one week before the start of the relevant event. Two sets of these tyres will be allocated to each driver for use during P1 and P2, and any such tyres must be returned to the tyre supplier before the start of P3.
There could also be weekends where teams get an additional set of that weekend’s prime tyre, for use on Fridays, which will also help to keep the track busy:
One additional set of ‘prime’ specification tyres may be made available to all drivers. Teams will be informed about such an additional set at least one week before the start of the relevant event. In this instance, the additional set will be available for use during P1 and P2. One set of ‘prime’ tyres must then be returned to the tyre supplier after P1, and two further sets of ‘prime’ and one set of ‘option’ specification tyres returned before the start of P3.
Finally, there are some tweaks to the safety car rules, as follows:
The safety car speed limit (an approximate 40% decrease in lap time) will now be enforced over two laps instead of one. The purpose is to ensure that cars are driven at a safe speed until they reach the safety car.
During a safety car period the pit exit light will remain green for the duration, unless the race is subsequently suspended.
Other than when the safety car has been asked to use the pit lane, no car may enter the pits while the safety car is deployed unless it is for the purpose of changing tyres.
Adam Cooper's F1 Blog 
Wouldn’t this green light at the pit lane exit cause more problems with cars exiting the pit-lane trying to force their way into the path of cars already following the safety car? E.g. motorway junctions…
Great idea of using different tires on Friday. It prevents top teams from _not_ running. 1) They would choose to hold their cards close to their chest in regard to their performance of the weekend’s compounds rather than pound around a green track. And 2) it gives non-race drivers (whether that be test, reserve, 3rd, or whatever designation of the week team XYZ chooses) *BADLY* needed experience.
On the other hand, get rid of safety cars except for monsoon starts. They were fine when used occasionally, without speed limits and pit lane stop lights. There is a standard ECU and FOM lays cable around every track for timing. Simply add another channel to FOM’s cable which dictates maximum RPM for the given section of track where yellow flags and lights are being shown. It’s a much simpler solution and more conducive to the spirit of the sport.
I know I’m replying to myself, but here it is, from Whiting himself. It supports removing all of the convoluted safety car regulations for speed limits and pit lights. Emphasis not in the original.
http://www.autosport.com/news/report.php/id/89956
“Other than when the safety car has been asked to use the pit lane, no car may enter the pits while the safety car is deployed unless it is for the purpose of changing tyres.”
Odd rule – so a car can change tyres during a safty car period – but not change a damaged wing?
Or – are you allowed to do whatever you like to the car, so long as you change the tyres as well?
It is ridiculous that the pit lane is open at all during the Safety Car period.
We had two great examples of why it shouldn’t be in 2010, and I’m surprised the FIA didn’t learn from this. I’m talking about Valencia, where the results were heavily manipulated by the timing of the SC, and Hungary, where every car pitting during the SC caused chaos, injuring one crew member.
There are also potential dangers of marshalls on track while cars race back to the pits. Even though there are laws against racing back to the pits, Liuzzi is on the record saying that that cars definitely did this at Valencia.
With refuelling gone, there is no longer a reason to leave the pits open. If a car has damage, they can be held at the pit exit until they are at the back of the pack.
OMG the powers that be in F1 are actually putting the cars on track! I thought they were to be admired while on stands in the garage.
Finally. It doesn’t take a genious to figure out that cars on track = spectators enjoyment. Cars in garage = car show.