This qualitative analysis compared focus group discussions of a carbon reduction target amongst users of different modes who travel to the same workplace. Grounded Theory analysis showed discussions expanded to wider carbon costs and more issues than those specifically described in the target. Differences in people’s perceptions of carbon emissions varied with travel mode: walkers and bicyclists showed high awareness and concern; car drivers and motorcyclists were more pessimistic and cautious of imposing restrictions, with a particular suspicion of ‘greenwash’ actions that do not provide actual benefits. Changing travel mode for carbon reduction was discussed cautiously by all groups, with concern over the legitimacy of efforts to influence a personal choice, and the need for a ‘balanced’ approach that would not punish personal decisions. Notably, participants discussed their current mode in terms of perceived autonomy, and feared losing this autonomy if they changed mode. This role of autonomy emerged as a central theme in discussions of carbon reduction, providing ideas for future interventions.