Papers to bring a private prosecution against George Square bin lorry driver Harry Clarke will be lodged within weeks.
Families of the victims will launch legal action after the Crown decided not to prosecute the former city council driver, whose lorry careered out of control and killed six people almost a year ago.
The bid is being led by Paul Kavanagh, of Gildeas Solicitors, who represent the family of Erin McQuade and her grandparents Jack and Lorraine Sweeney.
Erin, 18, Jack, 68, and Lorraine, 69, all from Dumbarton, died at the scene of the horror crash.
The bid for a private prosecution is understood to also have the support of the families of victims Gillian Ewing, from Edinburgh, and Jacqueline Morton, from Glasgow.
Sources have indicated that preparations are at an advanced stage and an application to the High Court is likely to be made before Christmas.
Detailed evidence at the fatal accident inquiry into the tragedy showed that Clarke had allegedly hidden repeated fainting incidents, dizzy spells, vertigo, worries about his heart, his weight and his general health from doctors, the DVLA and his employers.
The Crown Office had already decided that he would not face criminal charges before he gave evidence to the inquiry.