As someone who works for the railroad not all crossing have signals and crossings arms that come down. This is especially true in remote rural areas. Some crossings in the country side won't even have signs. Crossing signals are usually only found in towns, cities or heavily trafficked areas.
Where the hell do you live?! In the UK, Network
FailRail's Level Crossing standards mandate that no crossing is without 'protection', even if that just includes signs. Sure, for low-traffic areas they might just put in treadle-operated half-barrier crossings. For many of the small footcrossings across farms, there's at least a pedestrian gate and public telephone in place so that farmers can contact the signaller.
Edit: I also work on the railway. I am not a trainspotter or enthusiast. Really want to make that clear.
Most crossings will have at least a sign indicating a rail crossing, it can be rare not to see a rail sign but they are out there. The crossing arms are usually found only in towns, cities, or places of heavy vehicle traffic. The crossing arms aren't perfect, they do malfunction, ie not going down when a train comes, staying down after a train leaves or they will just keep flashing and dinging.
That's why you should still slow down and look before crossing a rail crossing, there could still be a train. Not to mention some crossings are sh*tty and can damage your car if you drive over them too fast.
I'll agree that no barrier pack is perfect. Whatever the method of warning/activation (whether it be treadles or electronic interlocking), failures can happen there as well. But, if they do it's considered a wrong-side failure, and it's pretty serious.
People do need to take caution around crossings. We had a safety meeting annually, and they showed us a lot of videos of near-misses and fatal collissions on crossings. Still, if a crossing is ever to fail or operate incorrectly, for whatever reason, that's a huge deal.