The research tests the effectiveness of "Carrots" aimed at promoting walking and bicycling against "Sticks" aimed at discouraging driving. Weighing the effectiveness of these two opposing types of transportation interventions against implementation challenges for practitioners.
Influencing city-scale travel demand frequently involves a combination of carrots aimed at encouraging desirable mode choices and sticks meant to discourage undesirable mode choices. The interplay of such carrots and sticks depends heavily on existing conditions such as infrastructure, land uses, congestion, and multi-modal options. To encourage bicycling and walking – non-motorized modes (NMT), US cities focus almost entirely on carrot interventions to improve infrastructure or social norms regarding NMT, but how effective are carrots alone at impacting mode choice? This research asserts that carrots have been only modestly effective at promoting NMT in the US, and this is in large part due to a lack of sticks to discourage alternatives to NMT, namely driving. Existing literatures provides case studies of European cities that employ a combination of carrots and sticks and also boast NMT mode shares far beyond that seen in the United States. Similar research is lacking in the US because of a lack of available sticks to study. Combining quantitative and qualitative studies, we answer two research questions: (1) are carrots or sticks more effective at influencing NMT, and (2) what is the difference in terms of ease of implementation between carrots and sticks? Findings indicate that sticks may be most effective at changing behavior, but raise transportation equity concerns while also facing the greatest opposition to implementation. Combining carrots and sticks, while more challenging than implementing carrots alone, may be the most appropriate strategy for realizing significant mode shifts toward walking and bicycling.