The probability 1 in 4,000,000 will result in an acident.
over a life time an average driver takes 50,000 trips.
what is the probability of an accident over a lifetime
You posted this question more than once. Look for my answer elsewhere. Your data refers to FATAL accidents, not ANY accident.
You will also find the problem worked out at:
http://www.algebra.com/algebra/homework/Rational-functions/Rational-functions.faq.question.125800.html