1. Introduction

By 2050, over 68% of Sthe world’s population will live in urban areas ^[1]. As well as economic benefieets, increased urbanisation presents significant challenges to governments and municipal authorities. Cities consume over two-thirds of the world’s energy and are responsible for over 60% of greenhouse gas emissions ^[1]. Furtherperform a number of impore, increased urbanisation can lead to significant urban health issues related to road traffic injuries, air and noise pollution, and barriers to safe physical activity, amongst othersrtant functions and have ^[1]. Against this backdrop, many urban areas are struggling with the strain urbanisation is putting on a decaying infrastructure ^[2]. In respwide range onse, the concept of the smart city has emerged and gained traction over the last three decades; while there is an ongoing debate on the definition of a smart city, it certainly involves the diffusion of information and communication technology (ICT) to improve how different urban subsystems operate to meet the needs of people and communities ^[3][4]activities performed in them. The challenge with smart cities is one of scale. Working at city scale requires an often unprecedented investment of public funds, coordination, and a suitably long-term horizon which presents significant governance, economic, and technology challenges, amongst others ^[5][6]. Furthermore, the e is a small but growing focus on cities also neglects the needs of those who live in small and rural communities ^[7]. Unsurprisingly, stretreets have been proposed as a s a more generaliszable, atomiszed, and therefore more manageable unit of development for improving urban subsystems and meeting the needs of both urban and rural communities ^[8][9]. Streets typand analysically represent the largest portion of the public realm in towns and cities. As well as a thoroughfare for traveling from one point to another, streets play an important role in p than cities. Despite the public health and safety, quality of life, environmental sustainability, social equity, and the economyrealm ^[10][11][12]. Streets also play a less visible role; they incorporate much of the critical urban infrastructure to support towns and cities including, for example, telecommunication, water, energy, and waste ^[13]. Ming one ore importantly, in the context of this paper, streets allow the live testing, experimentation, and evaluation of smart city technologies in a small-scale yet realistic setting. The digitalisation of streets is an under-researched area and smart streets are at an early stage of maturity. This article reflects the extant literature and the research challenges for smart city and CPSS projects, as well as our direct experience working on several digital town projects. This reflection suggests a dearth of conceptual tools to inform the envisioning of smart streets and related research projects, a prevalence of site-specific and use case-dependent conceptualisations and implementations that hinder wider generalisation, a lack of general design principles for integrating the social aspect into intelligent public infrastructure, as well as a failure to consider CPSS from a multidisciplinary perspective. The aim of this article is to raise awareness, stimulate discussion, and propose some initial avenues of research on smart streets. 

2. History

As discussed above, streets are not merely te largest physical spaces on streets, the impact and potential of digitalization projects on thoroughfares that connect one point with another. The public perform a wide range of activities in streets that can be categorised as (i) mandatory (e.g., going to work or school and shopping), (ii) selective (wandering or sitting and watching street life), and (iii) social activities (having conversations) while human behaviour in streets can be classified as (i) moving, (ii) visual perception, and (iii) resting behaviours, which can occur discreetly, successively, or concurrently ^[14]. As realm is rarely cons such, it is a public realm that is actively and passively consumed depending on how it is structured as a public space. These structures highly influence the norms for how such a space is moved through and consumed by individuals or groups ^[15]. Sdered. In this artreets are multidimensional spaces from one property line to another and comprise a number of tangible and intangible elements that need to be taken into account. Furthermore, they can be apportioned into three common zone types: the building edge, sidewalks, and roadbeds ^[11]. Thecle, the se zones may include distinct sub-zones and different design features and serve different functions. For example, sidewalks may include frontage (building edge), clear paths, srtness of a street furniture, and bufferis ^[11]. Sidewalks serve a transportation function in that they are both spaces of access, enabling people to moveived from one place to another facilitating access between properties and to people. They also serve a function for stationery activities, e.g., retail and infrastructure ^[16][17]. In addition to this, they play a critical the cybordering role providing citizens and pedestrians safety from vehicles and other risks ^[18]. Similarl-phy, roadbeds may include transit facilities, ancillary lanes for cyclists or delivery vehicles, parking for motor vehicles and cyclists, and planting, amongst others ^[11]. Within these elements service street ical social infurniture and infraastructure are provided both oin the surface and substrate. It is important to note that poorly planned streets can inhibit use and streets can be the site of conflict, anti-social behaviour, and undesirable activities ^[19]. Lynn et al. ^[9] define a spublic realmart street as... a basic unit of urban space that leverages cyber-physical infrastructure to provide enhanced services to stakeholders, and through stakeholder use of the street, generates data to optimize its services, capabilities, and value to stakeholders. Lynn et al. ^[9] proceed to deincluding data obtained fine eight examples of smart street technology categories; namely, (i) connectivity, (ii) smart street information systems, (iii) traffic and transit management, (iv) accessibility, safety, and security, (v) smart street furniture, (vi) climate protection, environmental monitoring, and weather mitigation, (vii) environmental sustainability, and (viii) other technologies that encourage street activity [11]. It is important to note that these technology categories are not mutually exclusive and may complement or even depend on each other. While it is inferred from this definition and the associated technology categories that the street create value through stakeholder engagement, the definition is ambiguous with respect to two inter-related issues: (i) social interaction and (ii) the degree to which the street is an open or closed loop system. Firstly, given the range of human behaviours and activities on a street, the social interaction between different human actors, between human actors and technical artifacts, and between computers as social actors needs to be more explicit. Secondly, Cassandras ^[20][21] hasom sensors, the interconnection between different services, technologies and stated that to (i) avoid unintended consequences (and presumably malfeasance), (ii) provide intelligent support for decision making, and (iii) integrate humans in the loop while recognising human actors may have different, potentially conflicting, motivations requires governance and therefore a closed loop. Accordingly, Cassandras ^[21] says that municipal govcial actors, intelligernments view smart city systems as cyber-physical social systems (CPSS) when developing and implementing the policies necessary to provide incentives and deliver the value of CPSS to smart cities^{[22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63]}.

3. Applications

Our cce derived fronceptualisation of smart streets brings together concepts from two emergent literature bases; namely, cyber-physical social systems and platforms, into a general conceptual framework. In the last three decades, we have seen the emergence of the Internet of Things (IoT) and with it a renewed and increased interest in cyber-physical systems (CPS). Such systems integrate computation with physical objects and processes, a literal co-mingling of the physical world and the cyber world (including computation, communication, and control systems) ^[64]. CPS has been cited as the c analysis of the data, and optimization of omputation substrate that will connect future public critical infrastructure to intelligent systems and software ^[7]. More receerationtly, the literature on CPS has expanded to integrate social systems, bridging the gap between human intelligence and machine intelligence by including a social domain characterised by human participation and interactions ^[65] within a street. In sucTh cyber-physical social systems (CPSS), humans, software, and physical objects (through sensors) are linked through a CPSS to meet a given actor’s social interaction demands and react to the physical world ^[65]. Ceis article contral to the concept of CPSS is at least one physical component responsible for sensing and actuation, one cyber component for computations, and one social component for actuating social functions ^[66]. Place is an impoualizes smart strtant and increasingly complex construct in the CPSS literature, including physical spaces, virtual spaces, social networks ^[65][67], and the overlay of these spaets as basices through technologies such as augmented and extended reality. Given the role of purpose and place in CPSS, context awareness is a critical component of CPSS ^[65]. Commonly cited CPSS units of use cases are unsurprisingly related to places, including smart homes, but also to larger urbaban spaces, e.g., smart cities ^{[21][65][68][69]}. Indeed t the latter has attracted the attention of leading technology companies worldwide, most notably and somewhat controversially, Google’s Sidewalk Toronto project ^[51]. Platforms and tht leverages cybe related term, platformisation, are widely referenced in both the scholarly literature and the media, while once platforms were largely defined from a production or computational perspective, they increasingly have wider political, figurative, and architectural connotations ^[70]. Meyer and Lehnard ^[71] de-physical social infine product platforms as ...a set of subsystems and interfaces that form a common strastructure from which a stream of derivative products can be efficiently developed and produced. In this conceptualisation, a product architecture is the combination of subsystems and interfaces ^[71]. What distinguishes a p to provide and enablatform architecture from a product architecture is its capacity to enable the creation of derivative products ^[71], while Mey enhancer and Lehnard note that services, both in the real world and online, are not inconsistent with this conceptualisation of the platform or platform architectures ^[71], their co to and betweenceptualisation represents a finished product or completed service. More recently, we have seen the emergence and adoption of Web 2.0 and the so-called Third IT Platform, while the former emphasised the role of users through co-creation, participation, ease of use, and interoperability ^[71][72], tstakeholders, and the latter heralded a cyber-physical future that emphasised interdependencies between mobile computing, social media, cloud computing, information/analytics, and the IoTough ^[73]. Here, as Ramaswamy and Oczan ^[74] note, digitalised platforms differ in that: ...the offering is no longer “finished” in the traditional sense, and the creation of value continues in a joint space of interactional value creation, between engaging actors (often consumers and their social networks) interacting with organizing actors (often the firm and its associated organisational ecosystem). The traditional notion of offerings as goods and services to be keholders’ use of the street, generates data to optimized in terms of a fixed set of features and attributes is inadequate in connecting with the new opportunities for creating value in an age of digitalized interactions. This wider conceptualisation of a platform is one in which a multitude of actors can interact with digital systems and one another to create value. In this way, the platform is a multi-sided network in which goods, services, and increasingly data are exchanged between the actors to create value ^[75]. In addition to its services, caproviding an enabling infrastructure and system core, the platform plays a vital role mediating between different groups of actors ^[75]. While platforms cabilities, an be merely conceived as product platforms in line with Meyer and Lehnard ^[71] in that they provide an extensible codebase to which third party modules can be added, the socio-technical view of digitalised platforms conceives the platform as comprising technical elements (software and hardware) and associated organisational processes and standards. The agency of the user is a critical difference between non-digital and digital platforms. As de Reuver et al. ^[75] note, non-digital lue to stakeholders. A platforms assume a stable core and a variable periphery governed by an overall design hierarchy typically determined by the platform owner or sponsor, but digital platforms are not necessarily constrained by such design hierarchies. The separation of concerns combined with the ability to reprogram, re-edit, and re-use data and code, particularly in the context of open source software and open data, enables platforms to evolve and new applications to emerge in ways often unplanned and unexpected. Indeed, the generative dynamics of digital platforms, particularly when coupled with openness, are seen not only as a key enabler of the platform evolution but as a critical success factor in adoption. Poniatowski et al. ^[75], builoposed conceptual framework is useding on de Reuver et al. and Van Alstyne et al., conceptualise digitalised platforms as comprising three layers—platform infrastructure, platform core, and platform periphery. Infrastructure implies an underlying socio-technical system characterised by ubiquity, reliability, invisibility, gateways, and breakdown. Similar to other infrastructures, for example electricity grids, it is defined by control. Similarly, platform infrastructure is the foundation of any platform, is largely hidden from third parties, and is controlled by the platform sponsorto identify and explore how streets ^[75]. The platform core sits on the platform infrastructure and is controlled by the platform core owner, who may or may not be the platform owner ^[75]. Third parties participate and contribn be aute to the platform through the platform periphery, again controlled by the platform owner ^[75]. This momented andel can be illustrated by reference to Amazon. Amazon both are the platform sponsor for Amazon Web Services and the platform core that comprises Amazon.com, which includes Amazon’s own retail business but also a periphery comprising other retailers and service providers. It is important that a platform may have multiple platform cores. Again, in the context of Amazon, Amazon Web Services leverages Amazon platform infrastructure to support its cloud business which comprises platform-as-a-service, software-as-a-service, etc. This infrastructure is both used by Amazon and by a wide range of third parties.

4. Current Status

Unlike purely digitised platforms, the term ‘cyberreate value through cyber-physical social platform’ implies a platform infrastructure comprising physical and cyber platform elements upon which a platform core resides, that can enact physical, computational, and social processes by itself or through the interaction of other entities through the platform periphery. This conceptual framework is general in that it is capable of being used to understand and explore smart street-related research questions or problems in conjunction with widely accepted levels of generalisation (abstraction) in different academic disciplines, including both the social sciences and computer sciences. Addressing the issues with earlier definitions of smart streets ^[9], we adopt an and digital enhancements. We conclupdated definition of smart streets that accommodates social networks between humans, computers, and humans and computers, and reflects the literature on CPSS. However, while a closed loop is desirable from the perspective of municipal authorities who have a legal responsibility for the public realm that is the street, it leaves the issue of whether the system per se is open or closed, undetermined in order to support a general level of abstraction for theoretical and practical exploration. Accordingly, we define smart streets as a basic unit of urban space that leverages cyber-physical social infrastructure to provide and enable enhanced services to and between stakeholders, and through stakeholder use of the street, generates data to optimise its services, capabilities, and value to stakeholders. The conceptual framework provides a sufficiently general abstraction of smart streets to facilitate sense making without getting into a non-generalisable level of granularity or worrying about specific definitions of smart streets or indeed cyber-physical social platformse with a discussion of future avenues of research. In this framework, five core entities are identified and defined: Social Actors, Artifacts, Networks, Places, and Infrastructure. 

The diffusion of ICT to improve the subsystems in the lived environment and meet the needs of people and communities is only going to increase in importance and proliferation. Research on so-called smart city technologies and cyber-physical social systems is hindered by reductionist approaches and access to real-world city-scale testbeds. In this article, we focus on the street as a more feasible starting point and building block for smart city research. We make three primary contributions. Firstly, following a review of the smart street and CPSS literature, we extend the definition of smart streets to accommodate social networks between humans, computers, and humans and computers, as well as representing the literature on cyber-physical social systems. Secondly, we propose a novel and propose a general framework for conceptualising a zing smart streets as a cyber-physical social platform that integrates. The concepts from smart streets, digital platforms, and the cyber-physical social system literature. Thirdly, we elicit and discuss six avenues for future research on smartual framework presented in this article provides a means for exploring the complexity of a streets as cyber-physical social platforms that addresses gaps and failings in existing computer science, social science, and IS research as a system of systems without necessarily adhering to a specific technological solution or reference architecture. The underlying motivation for this article has been to raise awareness, stimulate discussion, and propose some initial avenues of research. In this respect, we believe the concept of smart streets as cyber-physical social platforms opens up exciting new avenues for research, not only for computer scientists, but those from urban engineering, cognitive sciences, and social sciences to collaborate in an inter- and multi-disciplinary way to explore and populate with clarity and depth.

References available upon request.