Sharron supports the proposed minimum learning period but said: “We need the post-test safety precautions as well.”
The driver, Skye Mitchell, who was also killed, had passed her test four months earlier.
Sharron believes Caitlin “would still be here” if the UK had graduated driving licences which forbade newly qualified, young drivers from carrying passengers their own age.
“All the girls [in the car] were 18,” she said.
“This is the strongest element of a graduated driving licence that would save many young lives.”
The AA has welcomed the measures announced by the government, but said not introducing GDLs was “a missed opportunity”.
Its president Edmund King told the BBC that “all the evidence, from Australia, from Canada, from other countries” shows that limiting the number of same-age passengers in a car for six months “will save lives”.
He said of the learning period: “That will help, but the question is: does it go far enough?”
The road safety strategy will also include proposals for a lower drink-driving limit in England and Wales, to bring them in line with Scotland. Novice drivers would have an even lower limit, which is already the case in Northern Ireland.
The BBC revealed in October that further research into headlight glare would be included in the strategy.
