What would have happened without the campaign?

A favourable decision after collective action is not automatically an effect caused by that action. This methods note develops a counterfactual evaluation for a fictional workplace transport coalition, drawing on the Magenta Book, the GHG Protocol Policy and Action Standard, and the IPCC demand-side assessment. A pre-existing employer plan illustrates bounded contribution rather than exclusive credit, while invented arrival counts expose the assumptions behind before-and-after and comparison-group arithmetic. The analysis distinguishes mobilisation, decisions, implementation, sustained operation, and downstream climate effects. Participant protection and ethical constraints remain part of the design. No campaign result or emissions saving is claimed. The proposed approach supports honest learning from shared influence, partial gains, and unresolved demands without converting signatures into unsupported carbon totals.