Randall D. Knight — Kinematics in One Dimension: Problem Problem_70

I was driving along at $20\text{ m/s}$, trying to change a CD and not watching where I was going. When I looked up, I found myself $45\text{ m}$ from a railroad crossing. And wouldn't you know it, a train moving at $30\text{ m/s}$ was only $60\text{ m}$ from the crossing. In a split second, I realized that the train was going to beat me to the crossing and that I didn't have enough distance to stop. My only hope was to accelerate enough to cross the tracks before the train arrived. If my reaction time before starting to accelerate was $0.50\text{ s}$, what minimum acceleration did my car need for me to be here today writing these words?