Step 1:

Let $X$ be the random variable denoting the number of accidents involving taxi drivers in a year.

$X\sim P(3)$

$P(X=x)=\large\frac{e{-3}3^x}{x!}$

Step 2:

Probability that a taxi driver is not involved in any accident =$P(X=0)=e^{-3}=0.0498$

Out of 1000 drivers the expected number of drivers who will not be involved in any accident =$n\times probability$

$\Rightarrow 1000\times 0.0498=50$(approx)