Do you drive home from work the same way every evening? Perhaps there's a particularly dangerous curb you have to navigate, and every time, you notice a bouquet of flowers -- or multiple bouquets of flowers -- on the corner in remembrance of the people who died.
It's clear to you why it happened. The curb is a sharp one, and if someone isn't paying attention, they could drive right off the road. In a lot of cases, the people who cause these accidents are drunk. When you combine a dangerous curb with drinking and driving, the effects are often disastrous.