This is a millipede as it has two legs per segment, it could be a Pogonosternum, or a Solaenodolichopus, but its not possible to be definitive from a photo. Good siting, it would be nice to know if it was a Solaenodolichopus, as they were thought to be an introduction to the ACT from up North see https://researchdata.museum.vic.gov.au/BowerBird_Bugle/Edition_40.pdf