The unions want negotiations towards better pay and conditions, sometimes these demands are pretty transparent grift or make things unsafe, but usually they're just "Give us more money" and like, yeah, give them more money.

An example of making things unsafe: One of the railway unions took strike action to preserve 12 hour shifts for signallers. That might seem counter-intuitive, who wants 12 hour shifts? Well, you work 3 x 12 hour shifts, that's your week = 4 days per week off. Whereas if the safety reform demands max hour 8 shifts that's only 2-3 days off, so of course affected signallers hated that.

Why was it unsafe? Well humans can't really work 12 hours. We get bored & our minds wander, if it's dark and warm we fall asleep or stumble around dazed. And a signaller's job is normally pretty calm, you could do it half asleep and it'd be OK. "Ding ding" that's the last city express, pull 18, wait a beat, press buzzer, pull 19 and 25. But, sometimes it gets very exciting very fast, and that's why it's a job for a skilled human. "Ding ding" - the express, pull 18, it sticks, uh, what? Pull harder, still sticks. Er... now you should be wide awake, that express at 100mph is about to reach a Danger signal, is it because there's really danger? What should you do? But you are tired, it's been a long day, release 16 and that'll fix it right? Now 18 moves. But wait there's a loud noise and this needle is deflected, what did I do? And now the phone is ringing. We've just de-railed the back half of the slow coal train that was still crossing right in front of the express we've just given a green light. Hope nobody dies.

But this is the exception not the rule.