Honestly, I'm not convinced that there are unusually a lot of Jamaican r&b songs about trains! At least, if I look at the Tougher Than Tough: The Story of Jamaican Music CD box set (released on Island Records' Mango sublabel), there are a couple of songs about trains (Ken Boothe's 'The Train Is Coming', and Dennis Brown's 'Westbound Train' - neither of which you mention, so that's a couple more for your list!) - but only a couple. It's not like there's a whole disc of train songs. So I would judge that it's not a particularly dominant theme judging by that box set (or by flicking through my copy of Lloyd Bradley's book Bass Culture: When Reggae Was King).

You can also find plenty of train songs in other genres - if you look in a folk direction, there's Lead Belly's 'Midnight Special', and various songs about the train engineer Casey Jones, if you look in a country direction there's Jimmie Rogers' 'Waiting For A Train' or Johnny Cash's 'Folsom Prison Blues' (he hears that train a-coming). One of the founding documents of rock & roll is Elvis's version of Junior Parker's 'Mystery Train', and there's The Monkees' 'Last Train To Clarksville' (perhaps an influence on The Ethiopians' 'Train To Skaville', which looks like it was released a year later). Rod Stewart got on a Downtown Train (perhaps driven by Tom Waits), Paul Simon heard a Train in the Distance, and the KLF took the Last Train To Transcentral. The list goes on.

Pop, folk, American rhythm & blues, rock & roll, Jamaican R&B - there's just lots of trains. There's a few reasons for this. One is that trains do a lot of work semiotically for a musician: they can represent a lot of things, and they can be represented musically in a few different ways - they're polysemic in this sense. One way that you can represent trains musically, in particular, is that the train usually has a regular rhythm to it as it glides over the tracks, and so Johnny Cash's rhythm section for instance have been talked about as having a 'train rhythm', because of their regular chug. Perhaps the regular syncopated off-beats of rocksteady and reggae sometimes reminded Jamaicans of the rhythms of the trains in Jamaica.

Trains, too, are an important form of transport, in many parts of the world - they are a way for people to travel relatively inexpensively and quickly, at least compared to the upkeep necessary in keeping a private car, or on spending money on taxis or limousines. Cash's narrator in 'Folsom Prison Blues' is jealous of those people on the train he hears, as he, of course, is stuck in Folsom Prison. As you've alluded to, trains can be associated with hobos using them to travel away from prying eyes, and can have spiritual connotations; in the lyric for Curtis Mayfield's civil rights anthem 'People Get Ready', the Impressions sing "people get ready for the train to Jordan/ don't need a ticket, you just get on board", where the 'train to Jordan' is a revision of the idea of crossing the Levantine river of Jordan, a metaphor for spiritual rebirth (no doubt many a preacher of the era had said that accepting Jesus into your heart is a way to take a train straight to Jordan). In the context of civil rights, the train to Jordan that you get on if you join the civil rights movement will lead to a rebirth of sorts - of rights.

Another meaning inherent in the train is in its nature as a machine. Listening to reggae and rocksteady in 2022, it's important to realise that this music was, originally and essentially, a local form of American R&B - Jamaica was an island hundreds of miles from the US coastline, but it was not impervious to its influence; perhaps it is inevitable that the music of Black people in the US influenced the music of Black people in Jamaica (and, eventually, vice versa). For example, 'My Boy Lollipop' by Millie - the first big Jamaican worldwide pop hit in 1963/1964 - was a cover of a 1956 track by the American Barbie Gaye.

In regards to the train, the electric sounds in the rhythm & blues of the 1950s, often associated with Chicago, were to some extent a sonic metaphor for the new ways of life that African Americans found in urban places like Chicago after being part of the Great Migration. Which might regularly involve getting to work via metro trains. There's clearly a few songs about trains in American R&B of the 1950s-1970s, from Tarheel Slim's 'Number 9 Train' to James Brown's, 'Night Train' to Gladys Knight and the Pips 'Midnight Train To Georgia' - and of course the big soul music TV show of the 1970s was Soul Train.

So I would ultimately guess that the presence of train songs in Jamaican R&B, where it is present, comes from a few different factors. Firstly, Jamaicans might well simply be doing their own version of American R&B, and the lyrics about trains might simply be something they inherited with the musical style (Bob Marley and the Wailers, of course, covered 'People Get Ready' as part of a medley on their Exodus album, thus singing about trains). Secondly, the electric nature of the music, involving its machinery, and the nature of its musical rhythms, may have suggested to the Jamaican writing lyrics for these songs that trains would be a suitable topic.

Finally, in the time of rocksteady and reggae, Jamaica was a newly independent nation that had a particular legacy of English colonialism, and which certainly had some Black people who could relate to the 'train to Jordan' metaphors - Lloyd Bradley's Bass Culture discusses the rastafarian culture that was a big part of reggae/rocksteady as being pitched in opposition to the deference and uprightness/uptightness that was taught to Black Jamaicans as the proper way to behave. Similarly, given the structural inequality inherent in Jamaica, the civil rights movement metaphors might have resonated in some musicians and listeners.