Carbon fiber is like shrapnel. In countless races, this disintegration takes place without any injury to racers, track workers or spectators. In the Australian accident, spectator injuries were so minor no one had to be taken to the hospital. If the marshal had not been at a gap in the fence, put there so that marshals can quickly access the track, and if the wheel had not been on a trajectory through the gap, he would likely be alive today. It was a freak accident and likely one that won't be repeated.
T here are additional safety improvements that can be made.
One area to consider is the gaps in the track fencing. Photographers need gaps but they can be modest in size. Cornerworkers can move to the side of a gap, behind a fence, and move out only in an emergency. It is possible some gaps can be closed by quick opening gates. Costs need to be balanced against benefits.