I've seen at least one piece of light rail equipment that did not have continuous axles, but
rather wheels on the ends of arms suspended from the frame. Although these were not drive wheels, they were several cars ahead of the powered unit which would greatly change activation distances at grade crossings and block signals. This may be the issue here. Rather than the equipment being too light, the equipment is a light rail vehicle and may not
have solid axles. (By doing the wheels suspended from arms, the floors of the cars can be lower.)