Un vehículo independiente motorizado con una rampa para transferir cargo a un avión. Esta rampa puede ser también sin motor, movida por otro. Hay muchos tipo y tamaños. Las hay fijas también, son telescópicas que van de un puesto fijo al avión.

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According to the definition below,

if the ICAO and FAA call the area where aircraft are parked, refueled, unloaded, loaded and boarded an Apron, where does the term “Ramp” come from? Ramp is primarily a U.S. term, although universally accepted in the U.S., and used by tower controllers, it is not a term officially used by the FAA.

According to this, "Ramp" translates as "Plataforma de estacionamiento de aeronaves" here. Therefore, no "ramp" (in the sense of a slope) is meant.

In Spanish and for aviation, most English terms are used with no translation, or literally. Therefore, my take here is that they refer to any of the vehicles used there (fuel bowsers, luggage carriers, catering...) and that this translates as "transporte en rampa" or (more properly) "en área de estacionamiento de aviones"