haulage routes that had long been in existence, and from the omnibus routes that first ran on public streets in the 1820s, using the newly improved iron or steel rail or 'tramway'.
the low rolling resistance of metal wheels on iron or steel rails (usually grooved from 1852 on), allowed the animals to haul a greater load for a given effort than the omnibus and gave a smoother ride.
could only work so many hours on a given day, had to be housed, groomed, fed and cared for day in and day out, and produced prodigious amounts of manure, which the streetcar company was charged with storing and then disposing of.