On the 'impertinence of impermanence' and three other critiques: Reflections on the relationship between experimentation and lasting – or significant? – change

Experimentation, and street experiments in particular, have led to considerable academic and policy advances in sustainable and inclusive (mobility) planning over the past years. With increased popularity and confidence, the street experiments field has recently begun to turn to in-depth discussions on design and upscaling, more than questions of its own legitimacy or relevance. This commentary nevertheless explores four recurring critiques of (street) experimentation and proposes how looking more deeply at them might empower, rather than weaken, such initiatives. Engaging with these critiques is therefore not meant as a renewed criticism, per se, of (street) experiments. Rather, it recognizes that getting into the technicalities and specific designs and elements that might improve street experiments and their capacity to impact change advances knowledge in the field, but argues that advocates must not forget some key baseline critiques they might face - and be ready to either defend or amend their choices accordingly. This commentary is a call to be more creative and less conforming, and to come back again to the deeper motivations for what (street) experiments are meant to do; or develop a better understanding of those motivations. This commentary also leaves open questions that will require further research. Disconfirming some of the hypotheses emerging here would be no less interesting than confirming them. I hope the readers will thus see this commentary as an invitation for debating and exploring these critiques and reflections further.