>>856961>Safety equipment is not air conditioning, which is a needless luxury. A/C is safety equipment in many cases. You can't safely operate a locomotive for a full tweleve hour shift if it's 100+ degrees at 100% humidity inside the cab without huge amounts of water. It directly impacts the operator's preformance. What happens if they get heat stroke? Then you have a train (hopefully) e-braking and taking up space on a mainline for an hour or so until an ambulance and replacement crew can be sent out.
Given how ridicously cheap A/C is, there is no reason not to have it especially when the locomotive itself is a power plant and can supply more than enough power to cool (or heat) a cabin.
It's not safe to run a train in subzero weather without a heat source for the operator, and it's not safe to run a train in high temperature/high humidity weather without A/C.
This is especially true when truck, boat and plane operators all have A/C installed on their equipment. Every single modern office and factory has A/C.