@whitequark✧✦Catherine✦✧ It does! Individual locomotives all have unique five- or six-digit numbers, e.g. 43003, always printed somewhere on the body, where the first two or three digits represent the model and the last three are just sequential identifiers; and timetabled services are identified internally by train reporting numbers (informally "headcodes"), e.g. 1A37, though those are only unique within a particular region on a different day, not nationally. There are plenty more less widely-used identifier schemes too. Unfortunately most of this is not widely exposed to passengers through official channels, but there are plenty of enthusiast sites like RTT that expose open data