The equation you've used is finding time, not distance.
The equation to use in this case is:
[tex]v^2 = u^2 + 2as[/tex]
Where v is the final speed, u is the initial speed, a is the acceleration and s is the displacement.
Rearrange this to find s.
Remember that the driver is decelerating, so the acceleration is -2.68 ms^-2.