Ann Copeland, 45, and her daughters, Niamh, 10, and seven-year-old Ciara, died after their car skidded on a hydraulic fluid leak on a country road in early 2008.
A Fatal Accident Inquiry found the fluid probably leaked from a William Whyte Cargo Handlers' crane.
The haulier and mobile crane company was subsequently investigated to determine if they had proper safety practices in place.
They were found to be falling short of the standards expected.
Yesterday Scottish Traffic Commissioner Joan Aitken said the firm had since put road safety at risk by neglecting maintenance on the trucking side of the business.
She ruled the firm's licence should be restricted - from four vehicles to two for a period of three months - after managers prioritised crane maintenance and business expansion over lorry safety.
She said: "The sheriff in his determination of what procedures might have prevented the loss of life on the A92 that January 2008 effectively recommended procedures that are already at the heart of the safe operation of goods vehicles.
"Yet this operator did not have these procedures in place to the standard required by Vosa and the Traffic Commissioners. In the midst of successful development of a highly specialised service to the oil and wind farm industries, some basics were forgotten and lost sight of."
Mrs Copeland and her daughters were killed while travelling to school on the A92 Stonehaven to Dundee road in January 2008.
It later emerged that Mrs Copeland's car had skidded on hydraulic fluid. Since the tragedy her husband Barry, from Johnshaven, has been campaigning for a change to road safety rules after he discovered cranes and other machinery did not need to have an MoT test before going on the road.