Train tickets in Switzerland do not come with a seat allocation.
When you buy a ticket for a Swiss train, you buy the ticket for the transportation only, not for a seat. Trains in Switzerland are mass transit. You arrive at the station, get on the next train, and find a free seat. Just as you do in a metro or tube. And, do not worry, taking a train here is a very easy undertaking - you will understand what I mean after you rode a Swiss train.
You can make seat reservations but only for trains of category EC, IC, or PE. Not for IR trains which run between Lucerne and Zurich v.v.
The trains usually offer enough seat capacity that everone finds a seat, especially after peak hours as in your case. In Lucerne, do not board the first car at the rear of the train, as this car is usually the most crowded. I suggest you to board in the center of the train.
Antwort hilfreich? Danke für deinen Like oder Markierung als Lösung :: Reply helpful? Thank you for giving it a like or mark it as solution.