It tends to vary. The fact you can walk between the carriages of two former driving cars on V Sets, for example, seems like a death trap waiting to happen.
I've just had 5 days in Switzerland, travelling extensively by train - around 18 hours travel, excluding heritage lines. I heard a train horn sounded only once and apparently it's a rare occurrence. We were east of Lausanne alongside Lake Geneva and I noticed three or four people at the track side, apparently having come out of the lake. The train didn't slow down so I assume the warning sounded complied with regulations. There's no lineside fencing of course except where landowners have put up their own, and no yellow lines on platforms. There was a complete absence of safety and security announcements on trains and stations, but there were signs at Brussels Midi warning of pick-pockets!