From 40 years of experience in and around these areas many of the HAL Ops staff drive at excessive speeds far faster than is necessary. In some cases should they be involved in marshalling an a/c on occasions they arrive on stand late almost making a handbrake stop.
They do act as a law unto themselves, mind saying that I believe there is over 6000 vehicles airside, many areas are cramped and congested, roadway speeds are 20mph and a/c stand speeds are 5mph. I am sure all of us that drive regularly will know how easy it is to exceed speed limits, I guess this is also more the case at quieter times with less vehicles about and this would have certainly applied to T5 at this time of the morning.
Whatever the outcome it is very sad for all those involved and doubtless will lead to another raft of Airside Regulations! Overall vehicle accidents have decreased dramatically over the last 10 years much of that down to regulations and continuity training / safety days etc. However HAL, Met Police and Heathrow Airport Users group try to police the system there will still be errors.