Julia Mackay was airlifted to Raigmore Hospital
The death of Christina Fraser on the A9 in 2006 stands out starkly among the 28 prohibitions issued against haulier Munro & Sons (Highland) Ltd.
Events leading up to the accident are recounted in Traffic Commissioner Joan Aitken's decision.
She quotes Crown narrative from the court case against the company following the fatal accident.
The firm was transporting the digger to a quarry to test it before deciding whether to buy it or not.
Lorry driver Walter MacLennan and Munro & Sons (Highland) Ltd's contractors manager Andrew Gillies were involved in transporting the machine on a low loader.
Unknown to the two men, the digger's parking brake was ineffective.
Wheel chocks were not placed under its wheels and the two chains used to secure the 30-tonne machine were found to have a breaking strain of 4.5 tonnes each.
Ms Fraser and the driver of the car, Julia Mackay, were travelling home from work in Inverness and approaching the Tomich junction between Alness and Tain.
The low loader had turned off the trunk road at Tomich and was climbing the road to Newmore.
When it was 40m from the junction, the two chains broke under the weight of the digger and the machine "freewheeled" backwards, forcing the low loader's hydraulic ramps to the ground.
The Crown narrative said: "The loader, in neutral gear, unrestrained, uncontrolled, rolled off the trailer onto the A9 and into the motor car carrying the young ladies."
Ms Fraser was killed, while Ms Mackay was severely injured. She was airlifted to Raigmore Hospital in Inverness.
The Traffic Commissioner's written decision includes a remark attributed to Mr Gillies that old chains were never checked.