With regard to notices, usually we will ask the railway to give us an answer or fix a certain situation within a certain timeframe. It's not an immediate threat, whereas with a notice and order, we will usually impose some operating restriction. For instance, if it's a defective track, we will ask them to reduce the speed right away. If the equipment—locomotives and cars—is not in good order, they will not be allowed to use that equipment until it has been repaired.
The notice, for instance, is probably where an inspection wasn't done within a certain timeframe; however, we inspected the track and we know it's safe, but we will ask them to provide their own report within a certain timeframe.
So one gives you a period of time to fix it; the other one you have to fix right away.