56.— For the purposes of subsection (1) of section 34 and subsection (1) of section 46, the fact that any person—

( a) had an opportunity of avoiding the consequences of the act of any other person but negligently or carelessly failed to do so, or

( b) might have avoided those consequences by the exercise of care, or

( c) might have avoided those consequences but for previous negligence or want of care on his part,

shall not, by itself, be a ground for holding that the damage was not caused by the act of such other person.