Yes, it means "traffic safety". You can think of it as a reminder to drive safely, or as a charm to assure a safe trip....our version of a plastic Jesus on the dashboard. This sort of thing and this slogan is very common in Japan.
Here's one from a local Buddhist temple. I keep it in my truck:
And a laminated wallet version from a temple in Yamagata:
You can't go anywhere in Japan without seeing 交通事故 or 安全運転 or 安全第一 plastered all over the place.
Unfortunately, there is a cultural tendency to think that merely having a slogan is protection enough; one needn't necessarily do anything to implement it.