When Bloom takes his seat in the funeral carriage, the
narrative notes that "He passed an arm through the
armstrap." Such things do not exist today, but the
reader who is sufficiently focused to notice this small detail
might suppose them to be similar to the loops that now keep
standing passengers in subway cars and urban buses from being
thrown about––and such was indeed the case. The fact that
Bloom steadies himself in an as-yet unmoving carriage is
probably worth noting.
Although seatbelts were not widely installed in automobiles until the 1960s, having proved unpopular from 1949 onward, earlier kinds of passenger cars had featured a different kind of protective loop: many horse-drawn carriages and railway carriages had arm-straps hanging from their side walls which riders could grab when jostled. In a page on James Joyce Online Notes, John Simpson observes that "Arm-straps didn’t protect the passenger being thrown forward in the event of an accident, but they helped to prevent the passenger swaying about and knocking into fellow passengers when the carriage or car rocked about on bumpy roads." Simpson quotes from five works of literature from 1857 to 1933 that mention use of an "arm-strap" or "arm-loop" to counteract jolts or to escape from an overturned carriage. The last of these confirms that automobile manufacturers too installed arm-straps in their vehicles "as late as 1933."
It is typical of Joyce to notice and include such details of
everyday life, and here the detail perhaps aids his
characterization of Bloom. Having just remarked on his strange
fastidiousness about pulling the car door "tight till it shut tight"
(or "twice till it shut tight," in Gabler's text), the
narrative also notices his impulse to latch onto an arm-strap
before the carriage has even started to move. His innate
caution (in Cyclops Joe Hynes calls him "the prudent
member") disposes him not to take any unnecesary physical
risks, and his marginal position in Dublin society (so much on display in Hades)
might also incline him not to risk being thrown against the
man sitting next to him.