Question: When did helmets become mandatory in the tour de france?
Disambiguated questions and answers: question: When did yellow helmets for the leading team become mandatory in the tour de france?
What year did helmets become mandatory in the tour de france?
After what event did helmets become mandatory in the tour de france?
answer: 2012
2003
Kivilev's death
Natural Questions answer: October 2003 (from the Wikipedia article "Andrey Kivilev")