HDX antecedent

This is an 1875 bus! According to Old Woodies, the

1875 'Obéissante' built by French steam pioneer Amedee Bollee, sat twelve, weighed 5 tons, consumed 50 kilos coal per hour and cruised at 30 km/h with a peak speed of 40 km/h. [emphasis in source]

And you say you feel old ...

Notice the leaf springs, which don't seem to have changed all that much over the decades, are located outside the wheels!