Operator of HT#4 was headed down hill on the Ponderosa Ramp when the truck lost control and hit the berm coming to a stop perpendicular in the roadway. HT#504 was headed downhill on the Ponderosa Ramp behind the #4 truck. As the #504 proceeded downhill, driver indicates applied brakes and began to lose control turning sideways and striking the # 4 truck, sending it downhill.