What happens when a good idea goes bad? Consider Metro-North’s quiet car initiative. Sixteen years ago, a group of regular commuters on Amtrak’s early morning train to D.C. had an idea: Why not designate one car on the train as a “quiet car,” free from cellphone chatter and loud conversations? The railroad agreed, and the experiment proved a great success. Now all Amtrak trains in the Northeast Corridor have a quiet car.