Good morning.

I am currently setting up an HO layout using Marklin C track with a Z21 (black) controller and iTrain.

I am looking to install occupancy detection and was wondering what other members might recommend as being trouble-free and easy to set up detection systems.

Very many thanks for suggestions.

Alex

You may wish to expand on your meaning of this.

If you are using software and implementing some sort of block control then a block may be considered occupied by a "point" sensor (or even logically by the PC without any sensors) as the train enters the block.

If you do want to detect if an actual train (locomotive or power drawing wagon) is in the block/section you may use something like the m83-AC(sic) 60882 that detects based on current draw.
Note; this solution falls down if the track power is off

for non locomotive (no power draw) detection , 3 rail systems offer this passively by isolation the rails.
Note; this system falls down of you have wagons with isolated axles.

If your concern is loosing coaches (unexpected un-coupling), then a reed switch solution for the caboose with a magnet may offer a tracking solution.