Title: Privacy Assessment of De-identified Opal Data: A report for Transport for NSW,
Abstract: We consider the privacy implications of public release of a de-identified
dataset of Opal card transactions. The data was recently published at
this https URL. It
consists of tap-on and tap-off counts for NSW's four modes of public transport,
collected over two separate week-long periods. The data has been further
treated to improve privacy by removing small counts, aggregating some stops and
routes, and perturbing the counts. This is a summary of our findings.