I'd suggest you take 10mg, that dose shouldn't sedate you too much. I'd suggest you try that dose the day before you go on the train to get adjusted to the effects. Don't expect euphoria or a crazy high, it isn't that recreational. It does have recreational value but it isn't a party drug or something that will expand your mind. If you expect too much you'll just be disappointed. It should just make you a little drowsy, possibly make you sleepy, reduce your anxiety and relax your muscles. The people that get euphoria from it are generally the people that suffer really bad anxiety, like me. Benzos can get me "high" but not the weaker ones like diazepam, even though I like it. Diazepam builds up in your system.
The residual effects can last up to a day, even more, when you take it daily, especially when you abuse it. A single dose shouldn't last longer than 6 hours or so. Maybe a little longer, or even less.
When you get high on it, its very hard to hide it. In fact you may look just simply fucked up. Your eyelids get really droopy, pupils possibly pinpoint and red. May have a hard time connecting with things. Your head planted under your shoulders and your balance may be off. I'm talking when you get fucked up, not a therapeutic dose.
You shouldn't fall asleep on them if the dose is low enough and 10mg should be. If your not feeling relaxed from that dose then an hour later you could take another 5mg but no more than that.