A systematic review of the scientific literature has started for the “Smart Streets” research project and has already offered some interesting preliminary findings.
A systematic scientific review on the theme of Multifunctional streets has been underway. Multifunctional are the streets which can fulfil a multitude of functions; that are not only transport infrastructures, but also lively and inclusive public places, carriers of economic development and ecological corridors, which actively support ecosystem services. Last but not least they support a number of technical functions including street and traffic lighting, electrical power, signalization etc.
A first qualitative search in scientific literature, to set up the criteria for the systematic review, showed that there is no generally used term to describe these multifunctional types of streets. Different terms are used depending on the geographical context. For example, in the USA the term used is “Complete streets”, while in Australia it is “Smart roads”. “Boulevards” and “Liveable streets” are often used in the European context, as well as the older term “High streets” relating mostly to the UK. Even then, the main focus in the related literature is on the transport multimodality of the street, meaning the combination of different modes of travel, including cars, public transport, cycles and pedestrians, while all the other functions (social, economic, ecologic) are either missing or separately studied. The only exception is the “High streets”, were the main function addressed is the economic. A very related term coming from ecology is “Green streets”, where the ecologic function is dominant, but the transport and social function are also addressed.
The preliminary indication was that the multifunctionality of the streets is not a topic which has been studied a lot in scientific literature. Multimodality on the other hand is a growing subject especially in transport studies, as well as topics related to future mobility (Autonomous vehicles, Vehicular ad-hoc networks VANET, Intelligent Transport Systems etc).
3187 unique scientific papers were filtered from Web of Science and Scopus using the search words: (streets, roads, boulevards) and (multifunctional, multimodal, complete, smart, high, liveable, sustainable, green) in Title, Keywords, Abstract. The diversity of terms was adapted so as to broaden the search enough to include literature from all geographic regions, and so escape the bias of using only, for example, US-based research. Only scientific papers (articles and conference proceedings) of the last 10 years were included since the object of the study is a rather new development in the related fields of research and since the conclusions need to be relevant for current and future urban design and planning.
The first screening of the titles resulted to a shortlist of 1653 abstracts to be reviewed, in order to arrive to the final set of the scientific papers to be read and synthesised. From the reading of the first 1000 abstracts we are already able to make some interesting preliminary observations.
Our initial idea that the multifunctionality of the streets has not been addressed adequately in scientific literature is still valid. The notion of multifunctionality seems to be rather new and although it is sometimes implied or presented as a general vision of the future streets it has not been systematically studied. Only, in papers from ecology, is the term multifunctionality used to describe green areas, including green streets. There indeed the technical, ecological, social and economic functions are intentionally combined.
Out of the first 1000 abstracts, 410 were assessed as irrelevant to the focus of the review (e.g. large-scale freight, route planning apps, smart tolls and pricing, in-vehicle support).
From the remaining 590 abstracts, 69 focus on future trends of mobility (e.g. autonomous vehicles, VANET). In our final set of 521 abstracts we identify two main clusters of papers: one focusing on street design, design principles and street elements and usually referring to a case study (277 abstracts) and one focusing on the spatial, environmental and societal effects referring to empirical studies (144 abstracts). 29 abstracts refer to related policies (e.g. Complete streets, Safe roads to schools) and 28 refer to or introduce related indices and scores (e.g. Smart Street Walk Score, Pedestrian Safety Index, Liveability Index, Healthy Development Index, Bicycle Environmental Quality Index). The rest 43 abstracts refer to more principle, theoretical papers that discuss general ideas.
Almost all geographic regions are represented, from USA (48), Canada (16), to different European countries (23), Australia and New Zealand (7), but also China, Japan, India and other Asian countries (26) and last but not least South American (6) and African countries (7).
As was the initial indication, the different functions are addressed separately in literature, especially in the empirical studies. The Social function in relation to Health (e.g. physical activity, active travel, active mobility, walkability, bikeability) and Safety is dominant (106 abstracts). The Ecologic function is also quite highly represented (54 abstracts). The Economic function is mainly studied in relation to UK’s High streets and is otherwise unexplored. In the empirical studies a lot of attention is given to the different age groups where specific studies are focusing on specific groups from small children, to youth, young adults, adults, middle-aged and elderly. Gender, physical disabilities, economic status and ethnicity are represented but to a much lesser degree.
In the papers which present case studies from practice (e.g. designed streets and neighbourhoods, transformation of existing streets) the full street design is presented. However, again it seems that not all functions are included in the design intentions, although the full paper reading will tell us more.
The Technical function is quite well represented (184 abstracts) in literature, but mainly because of the large share of papers related to Smart street lighting (82 abstracts) and secondly, Smart material (28 abstracts). However, the Smart street lighting literature mainly refers to their advanced technology and, at times, to the multifunctionality of the lighting features and not to their placement in relation to the complete street design.
Last but not least, an important cluster of papers coming both from empirical studies and design case studies relates to Multimodality in transport, with 56 abstracts.
Based on the first 1000 abstracts, we were able to make a first profiling of the related paper. After the abstract reading is complete, we will be able to make a second assessment on where the general literature on the subject of street multifunctionality is trending, which are the common or recurrent issues studied, which are the clusters of themes emerging and what themes are missing or being understudied.