What do we know about sustainable urban transportation systems?

The short answer is not much.

Unfortunately, according to a systematic literature review by Karjalainen and Juhola (2021), the research is really inconsistent in how sustainability is defined and what indicators are used to measure sustainability. There are also issues with diversity and representation and how social and well being factors are considered.

Karjalainen and Juhola (2021) describe sustainable urban transportation systems as those that “address social, economic, and environmental issues in a balanced manner, and promote access, affordability, safety, equity, efficiency, and economic viability, while simultaneously minimising their emissions and other environmental impacts” (p. 660). I would add that culture is also an important part of a sustainable system but as this isn’t taken up frequently, it is unsurprising that it isn’t included here. Their definition emphasizes the interconnectedness of urban transportation systems. There really is not much of our lives in urban areas that isn’t impacted by transportation in some way. For example, we need to consider what transportation options there are to get groceries, attend educational institutions, access meaningful employment that also allows us to pay our bills, access healthcare, visit natural spaces, and spend time with our friends and community. And this all needs to be possible regardless of our mobility status.

In terms of the research, the majority of it has been completed in European cities (44 of 99). North America and Asia are almost even with 21 and 20 respectively. Australia and Oceania make up another eight. And South America (mostly Brazil) with just six. Further, most of these only look at one city. This means that there is no comparison. And because studies are all using different measures, it isn’t really possible to make comparisons after the fact. This is important because comparing multiple cases can reveal different insights compared to when you look at a single case. It can alert people to hidden relationships that aren’t apparent immediately.

Another issue is that most indicators have been identified by academic researchers. This might make sense if there had been really robust development of these indicators but, as mentioned, there hasn’t been. As a result, there would be significant value in bringing in more diverse stakeholders to identify potential indicators. This would also help increase the equity of these analyses.

A final issue is that there is a strong bias towards motorized transport in the research. Walking and cycling are included much less often than personal vehicles and public transportation. One might argue that motorized options have more environmental impact so this makes sense. Except that having better infrastructure for walking and cycling can reduce the need for motorized options and increase access for individuals with lower income. Therefore, they contribute significantly to a comprehensive understanding of sustainability in urban transportation.

Probably unsurprisingly, this is a relatively recent area of research interest. As a result, the quality and integration of the research should improve over time. This review by Karjalainen and Juhola (2021) identifies some really important places to improve that research so that we can hopefully get better policies and planning to improve current networks.