Enforcement?

There were half a dozen police hanging around on the platforms at the train station this morning. At first I thought they were selling raffle tickets. But no - it was all about not crossing the tracks when the alarm was sounding. ($250 fine - hmmm...)

But then when the 6:13 pulled in this evening, where had they all gone? Where were they when scads of us hurried off to our cars, even before the train had closed its doors and pulled away. Ding ding ding ding ding...

Another case of situation ethics, I suppose.