The World Motor Sport Council has now formally approved rule changes to accommodate extra Pirelli testing for 2017.
Details were agreed in a meeting between the FIA, teams and Pirelli in China, and the rule modifications were then passed by votes of the Strategy Group and F1 Commission on Monday.
As expected initial testing of 2017 compounds in 2016 sizes will be conducted with 2013 or 2014 cars before the focus moves to the new 2017 sizes fitted to “current” cars – which means 2015 or ’16 chassis – with suitably modified suspension. It’s understood that seven teams have indicated an interest in taking part in these tests, which will be subsidised by Pirelli.
The FIA noted: “The further testing was deemed to be essential for the purpose of developing the new tyre sizes permitted by the 2017 F1 Technical Regulations.
“The changes will allow 25 car days of testing with current cars, fitted with 2017 tyre sizes, in 2016, 2017 and 2018.
“In addition, there will be an opportunity to test prototype 2017 tyres (in 2016 sizes) on 2013 or 2014 cars – these tests on older cars only apply in 2016.”
The further testing was deemed to be essential for the purpose of developing the new tyre sizes permitted by the 2017 F1 Technical Regulations.
The changes will allow 25 car days of testing with current cars, fitted with 2017 tyre sizes, in 2016, 2017 and 2018.
In addition, there will be an opportunity to test prototype 2017 tyres (in 2016 sizes) on 2013 or 2014 cars – these tests on older cars only apply in 2016.
Adam Cooper's F1 Blog 
Nothing to do with this piece Adam, reading from the side-bar again.
My mind’s becoming boggled that a person like Charles Whiting who continues to run the show, whilst demonstrating obvious failings in appreciating safety matters, gets to pontificate on future safety.
The man can’t get it right NOW, for heavens sake!