The Arnold rapido track was distinctive.  The rails were chemically etched to make them a more realistic brown color.  The crossties were also a more realistic shade of brown.  In addition, the rail profile was more rounded; some would say that this was not realistic, but Arnold promoted this design as being less likely to get dirty, and dirty track causes operational problems.  The track is also distinctive in that the rail ends at each end of a track piece are staggered rather than flush; with the joiners attached, each track end is flush.

     In the earlier days of the Arnold rapido product line, the track switches had their operating mechanisms attached; starting in 1967, these switches were redesigned.  They would later return to a permanent attachment arrangement of the machines.  In most cases, rapido switches were current routing, although Arnold later offered a version that did not have this feature. In the earlier days, Arnold also offered both an electrically operated and a manual uncoupler, later dropping the manual version.

     At the first, only one radius of curved track was offered (R1). By 1963, there was a second radius (R2) offered so the enthusiast could operate double track main lines.  Later, in 1966, additional track radii were offered (R3, R4). These were added at the same time that the passenger cars were made longer to achieve more realism

     The original sharp curves of the rapido line were to later cause problems.  The addition of curves R3 and R4 would solve this issue.

Inch dimensions are approximate.