In 1992, Simon-Duplex introduced the D500R, a 3 axle version of the D500 Vanguard chassis. It came standard with a 4 door enclosed 6-person aluminum cab. Available options included additional seating for up to 10 firefighters. The D500R maintained the split cab of the D500 which allowed the forward section to tilt providing access to the engine.
The D500R was intended for aerial ladder trucks and other large apparatus. The chassis was available until the late 1990s.