Persuasion is often seen as one of the most influential ways to achieve a desired result. As Cass Sunstein and Richard Thaler wrote in their bestseller Nudge there are many occasions where you can use persuasion – putting the fruit and veggies at eye/hand level and the chips further way – as a way to try to change behavior without forcing the desired change.

On a more concrete local level the D.C. bag tax is a great example of Nudg-ing at work. Plastic bags were a major problem in the Anacostia so local leaders implemented a small fee in the hopes of promoting reusable bags and curbing the use of plastic bags (and to raise some revenue of course). In this case the Nudg-ing worked. Outstandingly. The city raised $2 million in revenue but more impressively the number of plastic bags used dropped from 270 million to 55 million.

So Nudg-ing can work. Another more surefire but perhaps less democratic way to get things done is through mandate. Mandates are often needed to make change happen when the costs of a behavior change and the benefits are perceived as out-of-balance or simply not well understood. Climate change is such a case and that’s why many countries mainly in Europe but elsewhere as well have mandated certain levels of greenhouse gas emissions cuts. Persuading may be preferable to mandates in an ideological manner but leaders realized that waiting on behavior change through persuasion was likely not a choice on an issue of immediate concern.

Europe is now discussing taking a similar approach to transportation policy. Although many European cities have far higher transit usage than their American counterparts many of them are much denser and therefore congestion and pollution from auto transport are problems there just as they are here. As Alttransport explains Paris is one of the first cities in Europe to consider outright banning gas-guzzling SUVs from the city center. We won’t see the results until such a ban is put in place but an SUV is pretty easy to spot so we can assume it would achieve the desired result. London and Stockholm have taken the persuasion approach by implementing congestion pricing plans for cars entering parts of the city for years with very positive results on emissions and congestion. Is either the persuasion or mandate approach inherently better than the other? Should both be options to be used in different situations?