The construction sector typically contributes circa 13% to the global GDP (McKinsey and Company, 2017). It generates employment, creates and improves infrastructure, and supports business. Contributing substantially to socio-economic development, the sector’s operations exemplify significant resource consumption. As of 2019, the construction industry represented 35% of global energy consumption, in turn contributing 38% to global emissions (UNEP, 2020). These stem from upstream contributors viz embodied, including construction related energy (circa 5–36% for conventional buildings, and 10–83% for low-energy buildings) (Chastas et al., 2016), the rest being downstream recipients (Built Environment operation and maintenance) of the construction process. Figure 1 illustrates the Life Cycle Energy Analysis of a built asset.

The sector exhibits deep rooted fragmentation (Shakantu and Emuze, 2012; Guerlain et al., 2019b; Riazi et al., 2020; Jones et al., 2021). Fragmentation manifests at two levels viz at the Industry level through segregation from a relatively large number of small firms, and Project level due to disintegration of construction process and entities (Alashwal and Abdul-Rahman, 2014; Alashwal and Fong, 2015). Logistics is an interdisciplinary domain that forms a substantial component of the complex Construction Supply Chain (CSC) both in terms of project management and costs (Ying and Tookey, 2014). Precluding continuity and an integrated approach, fragmentation manifests as limited coordination and integration from ambiguous division of responsibility, leading to process inefficiencies (Alashwal and Fong, 2015). The resultant increased resource overheads create sustainability concerns. Comprised of diverse elements from transportation to warehousing and management of stocks (Szymonik, 2012, p. 12), logistics present substantial optimisation opportunity for the sector, through both strategic as well as operational mechanisms.

Transportation is the single largest element of logistics (Bowersox et al., 2002, pp. 32–34; Madadi et al., 2009), as a result of most other logistics processes except warehousing being business processes and not physical ones (Szymonik, 2012, p. 12). Construction materials being low cost/high volume compared to other industries (Lovell et al., 2006; Ying and Roberti, 2013; Balm and Ploos van Amstel, 2017; The Bellona Foundation, 2020), transportation forms a significant component of construction logistics. In addition to energy consumption, emissions, and costs (Smith et al., 2003; Szymonik, 2012; Ying et al., 2014), other transport externalities across sustainability domains may be direct (e.g., pollution, noise, congestion), or indirect (e.g., loss of ecosystems, health impacts, reduced quality of life) (Chatziioannou et al., 2020). Improved sustainability can, therefore, be achieved by optimising construction logistics through its transportation function.

Based on assessments undertaken by various agencies in the area of climate change, it is anticipated that transportation will contribute to approximately 60% of emissions by 2050 (IPCC, 2014a). Analysis also shows that freight transport is one of the most difficult sectors to decarbonise, not for lack of options, rather for challenges in deploying at the scale needed to achieve significant carbon reductions (Guerin et al., 2014; McKinnon, 2018).

New Zealand has peculiar physical attributes (Dani et al., 2022) viz its geographical isolation (Naismith et al., 2016), a deregulated market (Khan and Lockhart, 2019), sparse population, a low-density urban development strategy, and a resultant elongated sprawl with “urban villages” (Silva, 2019) strung out longitudinally along the two major islands. Logistics is the single most important domain keeping the country ticking, the end of an international logistics chain at its entry points only marking the beginning of extensive internal ones. The peculiar constraints typified in New Zealand restrict circa 93% freight movement to roads (a third of it construction related) with 99% fossil fuel (diesel) dependency. Market dynamics constrain improved technology, compounding the issue.

Freight transport decarbonisation is a high priority in the government’s climate change response for achieving New Zealand’s 2030/2050 carbon targets. The government’s strategy seeks 25% reduction in emissions from freight transport by 2035, amongst other objectives, towards greening/decarbonising freight transport (Ministry for the Environment, New Zealand Government, 2021). The strategy adopts the Avoid-Shift-Improve framework (Transformative Urban Mobility Initiative, 2019) and develops three themes to group together opportunities within this framework, with one of the three focussing on freight transport. It identifies Supply Chain (SC) efficiency, transport optimisation, data/information sharing, collaboration, and legislation/regulation as decarbonisation enablers, however, falling short of specific pathways, seeking further research to arrive at concrete implementation measures (Ministry of Transport, New Zealand Government, 2021). It is this gap that has provided the opportunity for the formulation of a research framework for implementation of the government’s strategy.

This study aims at suggesting a research framework for greening/decarbonisation of construction transport aligned to New Zealand realities based on the government’s adopted strategy. It is driven by the preponderance of road transport in construction logistics that supports optimisation, and the implicit onus of resolving construction logistics issues on the construction industry, rather than on those ordinarily responsible for managing city logistics (Janné and Fredriksson, 2019). Construction transport presents substantial sectoral sustainability improvement opportunities across a wide spectrum of initiatives from restructuring logistics at the strategic end to the introduction of cleaner transport technologies at the operational boundary.

The CSC adopts its characteristics from the nature of the construction industry viz Convergence of the SC directing all materials to the construction site, where the product (the built asset) is assembled; Setting up of the “manufacturing plant” around the single product (the built asset), unlike manufacturing, where multiple products pass through the manufacturing facility; A temporary SC involving repetitive reconfiguration of project organisations (causing instability, fragmentation, and delineation of design and construction) (Wegelius-Lehtonen, 2001; Dubois and Gadde, 2002; Naismith et al., 2016); and, A one-off and unique product, therefore, a “make-to-order” SC (Seth et al., 2018; Guerlain et al., 2019b; Riazi et al., 2020). The primary actors in the CSC are Owner, Architect or Consultant, Contractor, Sub-contractors, Suppliers, and User (Vrijhoef and Koskela, 2000).

Logistics provide a decision-making framework integrating inventory, transportation, warehousing, materials handling and industrial packaging, manifesting through physical flow, and management of goods/services and accompanying information, in an interdisciplinary environment. Major logistics activities are transportation (movement), storage (warehousing), industrial packaging, manipulation of materials, control of stocks, order fixing, demand forecasting, production planning, procurement, customer service, location of facilities, and management of waste. Logistics processes enable physical performance of logistics functions. “A logistics process may be considered to be an orderly time sequence of successive conditions and changes; a set of logically related activities and tasks, to achieve a business result; or, transformation of input data into output leading to change, considering value addition to a product or service. Logistics processes are specified temporally and spatially, in the field of the physical flow of goods/services, flow of associated information, and associated risks” (Szymonik, 2012, p. 23). Logistics, peculiar to the construction domain, may be defined as:-

- “…a process of strategically managing the procurement, movement and storage of materials, parts and finished inventory (and the related information flows) through the organisation and its marketing channels in such a way that current and future profitability are maximised through the cost-effective fulfilment of orders” (Wegelius-Lehtonen, 2001).

Figure 2 illustrates the construction logistics domain in relation to the main actors.

Construction logistics involve the preparation, management, coordination, and control of product flow from raw material processing to final utilisation in the finished project and reverse logistics of waste removal and disposal (Agapiou et al., 1998; Ying and Tookey, 2014). The components of construction logistics are (Jang et al., 2003; Sobotka et al., 2005; Ying et al., 2018; Janné, 2020):-

- Whole-project Logistics Sees the building site through the lens of a production system. It is a member of many logistics chains, executing complex processes within the constraints of budget, space, and time.

Construction logistics form part of complex systems with multiple stakeholders, and a wide range of simultaneous activities, processes, and systems in action, on- or off-site. A generic construction logistics model groups together planning and organisation (inter-organisational relationships), transportation, and site activities (Janné, 2020). Activities within these domains typically perform the roles of establishing clear SC - construction site interfaces, possible integration of the construction site with the SC, increasing efficiencies of the SC and site processes/activities, local stakeholder coordination, and value addition. Optimisation requires a very high degree of awareness and coordination/integration. Some of the major logistics challenges in construction are: Unclear division of responsibilities between the SC and the Site; SC inefficiency; Inefficient on-site logistics; and, Lack of coordination (Construction in the Vicinities Innovative Co-creation, 2018).

Construction characteristics distinctively influence logistics viz Each site, being unique and temporary, needs a new logistics setup (Wegelius-Lehtonen, 2001; Dubois and Gadde, 2002; Naismith et al., 2016); Sites being material intensive and supplied on an irregular basis (Kim and Nguyen, 2018); Construction activities being sequential, transmit delays, errors, and inefficiencies through all activities; and, Varying operational and management philosophies, and inefficient resource utilisation as a result of fragmentation of the industry (many construction companies, suppliers and Logistics Service Providers (LSPs) working in different temporary construction consortia) (Construction in the Vicinities Innovative Co-creation, 2018).

Transport is the largest component of logistics (Bowersox et al., 2002), a result of most other involved processes (except warehousing) being business processes and not physical ones (Szymonik, 2012, p. 12). The volume of construction material required for a project, its sustained delivery aligned to the site requirements, absence of planning and coordination/communication, typically small deliveries, low cost/high volume nature of construction materials, and transport externalities (Lovell et al., 2006; Ying and Roberti, 2013; Balm and Ploos van Amstel, 2017; The Bellona Foundation, 2020) present significant challenges.

An overview of freight transport with specific reference to urban goods distribution is essential as a primer to construction transport. The systemic framework of Urban Freight Transport (UFT) comprises three components viz Demand (for goods produced at places other than at the demand location, and requiring transportation), Supply (for meeting the demand by supplying logistics viz facilities and transport), and Context (logistics operations in facilities, and actual vehicle movements resulting from the interaction between demand and supply). The physical environment, in which demand and supply take place, defines the contexts and domains in which different SCs operate. Each of these components can be linked to one or more stakeholders viz Receivers (generators of demand for goods and, therefore for transport on the demand side), Shippers (send goods to fulfil this demand), LSPs (undertake logistics operations and actual deliveries as a direct result of the interaction between Receivers and Shippers). Contextual movements are regulated by Local Authorities, and the physical environment where all this takes place, is inhabited by Citizens (Kin et al., 2017; Guerlain et al., 2018; City Vitality and Sustainability, 2020; Diana et al., 2020).

Deliveries to construction sites are distinctly different from consumer goods movement, distribution, and delivery. Construction sites are material intensive and, irrespective of their size, need supplies to be aligned to their requirements, which may be irregular (Kim and Nguyen, 2018). Carriers attempt to be as service-oriented as possible, ignoring the negative social and environmental impacts this method of working might have. European Union (EU) transport data estimates the contribution of construction material transportation as circa 50% to European freight transportation (Balm and Ploos van Amstel, 2017), while another estimate places construction transport as circa 30% of urban freight transport (Guerlain et al., 2019b; Muerza and Guerlain, 2021), benchmarks for understanding the contribution of transportation to construction logistics. Illustration of the CSC in Figure 1 evidences the significance of the transport function in the construction domain (Fredriksson et al., 2020).

Construction transportation being road dominant, is achieved primarily with motorised vehicles. By virtue of the sheer volume of the material to be transported, it consumes significant amounts of energy, and generates large amounts of emissions, a substantial negative environmental impact of construction logistics. While contributing to only 20–30% of road traffic, goods transport consumes 40% of urban oil, emitting 80–90% logistics related carbon and 16–50% of overall air pollutants (McKinnon, 2010; Lindholm and Behrends, 2012; Khaled and Alam, 2016). Construction materials being low cost/high volume compared to other industries (Lovell et al., 2006; Ying and Roberti, 2013; Balm and Ploos van Amstel, 2017; The Bellona Foundation, 2020), transportation forms a significant component of construction logistics, typically contributing to more than half the logistics costs (Szymonik, 2012), a fifth of the energy consumption (Smith et al., 2003), and a tenth of the greenhouse gases of the construction sector (Ying et al., 2014).

Other transport externalities across sustainability domains may be direct (e.g., pollution, noise, congestion, etc.), or indirect (e.g., loss of ecosystems, health impacts, reduced quality of life, etc.) (Kohn and Brodin, 2008; Browne and Allen, 2011; Bretzke, 2013; Morana et al., 2014; Behrends, 2015; Vrijhoef, 2015; Kin et al., 2017; Janné and Fredriksson, 2019; Chatziioannou et al., 2020). Freight transportation is road dominant and based on motorised vehicles, which have externalities far out of proportion to their numbers, and form one of the least sustainable transport modes (Khaled and Alam, 2016). Improved sustainability can, therefore, be achieved by optimising the transportation function of construction logistics through the lens of the following attributes:-

- Externalities “Transport externalities refer to a situation in which a transport user either does not pay for the full costs (e.g., including the environmental, congestion or accident costs) of his/her transport activity or does not receive the full benefits from it” (Director General for Transport, European Union, 1995, p. 4); “The crucial importance of transport externalities arises from the fact that, in a market economy, (economic) decisions are heavily dependent on market prices. However, when market prices fail to reflect existing scarcities (clean air, absorptive capacity of the environment, infrastructure etc.), the individual decisions of consumers and producers no longer add up to an outcome that provides maximum benefits to society as a whole. Thus, pricing on the basis of full social costs is a key element of an efficient and sustainable transport system” (Director General for Transport, European Union, 1995, p. 5). The relationship between transport and sustainability is paradoxical; while supporting mobility, transport is invariably and intricately linked to externalities e.g., Emissions, Use of Non-renewable Fuels, Waste, Loss of Ecosystems, Congestion, Noise, Accident Risk, Gridlock, Air/Water Pollution, Public Health, Damage to infrastructure, and Reduction in QoL of Life, to name a few (Kohn and Brodin, 2008; Browne and Allen, 2011; Bretzke, 2013; Morana et al., 2014; Behrends, 2015; Vrijhoef, 2015; Balm and Ploos van Amstel, 2017; Kin et al., 2017; Janné and Fredriksson, 2019). Table 1 illustrates the externalities associated with road freight transport and their inter-se associations.

In addition to the objectives of maximising of profits along with minimising of costs and lead times, logistics systems have evolved from minimising the Total Environmental Impact (Kohn and Brodin, 2008) to minimising the Total Impact (which includes Safety and Security inducing direct and short-time impacts, e.g., Accidents; Environmental impacts, both medium- and long-term; System characteristics impacting the management of the system and transport operation processes; System support in terms of infrastructure, SCs, upstream and downstream processes that impact environment and society; and, Unsustainable resource use) (Rohács and Rohács, 2020).

From the discussion so far, three aspects of construction transport support its optimisation i.e., manner of its employment, characteristics of the SC, and technology.

The direction of discussion being sustainable logistics, with the transport component forming its primary unsustainable element, it is pertinent to define a sustainable transport system viz “A sustainable transport system is one that throughout its full life-cycle operation, allows generally accepted objectives for health and environmental quality to be met, for example, those concerning air pollutants and noise proposed by the World Health Organisation (WHO); is consistent with ecosystem integrity, for example, it does not contribute to exceedance of critical loads and levels as defined by WHO for acidification, eutrophication and ground level ozone; and does not result in worsening of adverse global phenomena such as climate change and stratospheric ozone depletion” (OECD, 2002, p. 16). Figure 4 illustrates the key elements of a sustainable transport system.

UNEP defines a green economy as “one that results in improved human well-being and social equity, while significantly reducing environmental risks and ecological scarcities. In its simplest expression, a green economy can be thought of as one which is low carbon, resource efficient and socially inclusive” (Fedrigo-Fazio and ten Brink, 2012, p. 4). The OECD Green Growth Report defines green growth as “fostering economic growth and development, while ensuring that natural assets continue to provide the resources and environmental services on which our well-being relies” (OECD, 2011, p. 4).

Both operate on the basis of development within environmental limits, which is also the universally understood meaning of the term “Greening.” In the transport domain, it is invariably construed as consisting of measures which reduce emissions from the tail pipe, therefore, localising focus on transport technologies. The concept is deeper and more involved than just technology, though technology does form a significant part of it. “Greening” implies “redesigning systems so that–in their functioning–they require less energy and materials, and produce less emissions while improving wider well-being goals” (OECD, 2021, p. 11). This discussion will consider “greening” as any measure which reduces emissions from freight transport and consider it synonymous with decarbonisation strategies.

Four fundamental frameworks for freight transport de-carbonisation are the Green Logistics Framework, the A-S-I/A-S-I-F Framework, the TIMBER Framework, and the IF-TOLD Framework. A discussion of these frameworks is essential to align their dimensions to the three aspects of construction transport presenting the “greening” opportunity.

Out of the above four frameworks for freight transport de-carbonisation, the A-S-I framework presents itself as the most overarching framework. Minimum attribute specificity makes it flexible and versatile to circumscribe more than one de-carbonisation dimensions within each of its attributes, at the same time associating more than one attributes with a particular dimension of the other frameworks, resulting in a multi-dimensional application matrix.

Based on an integration of the four frameworks, a solution space consisting of five focus areas emerges viz management of freight demand, smart use and combination of transport modes, sharing and maximum utilisation of assets, energy efficiency of assets, and use of lowest energy source to the extent feasible. The individual elements comprising each one of these are as follows (McKinnon, 2018; Punte et al., 2019):-

- Freight demand Reducing the freight transport intensity of economic activity (SC restructuring, localisation and nearshoring, decentralisation of production and stocking, dematerialisation, and influencing consumer behaviour).

The major stakeholders, (as in the case of smart city initiatives of which smart transport with de-carbonisation as a subset, is an integral part) form the Quadruple Helix (Borkowska and Osborne, 2018) for de-carbonisation/greening delivery. Each one of the above focus areas needs to be seen in a different perspective by the four major stakeholders in the Quadruple Helix (Punte et al., 2019) i.e.:-

- Government Regulation, pricing, subsidy, technology induction, emission/energy norms, infrastructure, and alternative mode development.

This aspect is of significance in the construction transport domain, since the implicit onus of managing construction logistics falls on the construction industry, (unlike city logistics whose responsibility is assumed by city managers), while the benefits are reaped by the city as a whole (Janné and Fredriksson, 2021).

Before the New Zealand context of freight transport is discussed, the peculiarities of construction transport need to be emphasised to provide context to the development of a research framework. Construction transport is a sub-set of freight transport however, it differs in terms of the impact of the nature of the CSC (primarily fragmentation and bespoke nature) (Alashwal and Fong, 2015; Guerlain et al., 2019b; Jones et al., 2021), peculiarities of employment patterns on a construction project (Ying et al., 2014; Sezer and Fredriksson, 2021), the spread of transport configuration peculiar to the construction industry (Guerlain et al., 2019a), and the onus of managing construction logistics being on the construction industry and not those managing city logistics (Janné and Fredriksson, 2019).

New Zealand’s freight logistics are driven by its peculiar spatial, market, regulatory, and economic attributes (inter alia geographical isolation, deregulated market, import dependency, small regional extent, long transits, small market/economy, non-implementation of vehicle emission norms/standards etc.) (Ying et al., 2014; Khan & Lockhart, 2019; Chapman and Howden-Chapman, 2020). While various implementation methodologies have worked effectively in de-carbonising freight transport in Europe, North America, and Asia, New Zealand’s peculiarities prevent their wholesale adoption.

93% of annual freight tonnages are moved by road-based transport. Diesel-powered freight transport (including Light Commercial Vehicles) produces 42% of New Zealand’s transport GHG emissions while accounting for only 26.1% vehicle-kilometres. A third of New Zealand’s freight transport is construction related. With a 99% fossil-fuel dependency, it exhibits about three times higher emissions intensity than other forms of road transport. Construction loads contribute to about a third of the freight tonnages (Ministry of Transport, New Zealand Government, 2020a, 2020c). To meet the 2050 Climate Change targets, de-carbonisation or greening of the road transport sector is critical (Ministry for the Environment, New Zealand Government, 2021). Freight transport, including construction transport, forms an important component of this de-carbonisation endeavour.

The Climate Change Commission in its “Advice to the New Zealand Government on the first three emission budgets” recommends uptake of electric vehicles (EVs), a shift to low carbon fuels (including hydrogen as a fuel), improving the efficiency of vehicles and freight movement, adoption of the A-S-I framework, optimising existing systems, end-to-end integrated transport planning, and formulation of a “National Low Emissions Freight Strategy” for investment and infrastructure to deliver a low-emissions freight system as strategic directions for de-carbonising the heavy transport fleet. It also emphasises policy to support co-funding pilot and demonstration projects for unproven technologies, sharing learnings with industry, and supporting adoption at scale of successful pilot projects (Climate Change Commission, New Zealand, 2021).

The Ministry for the Environment, New Zealand Government, in its “Transitioning to a low-emissions and climate-resilient future” consultation document seeks 25% reduction in emissions from freight transport by 2035, reduction in the emissions intensity of transport fuel by 15 per cent by 2035, integrating land use, urban development and transport planning and investments to reduce transport emissions, implementing mode-shift plans for urban areas, accelerating de-carbonisation of trucks, and developing a “Freight and Supply Chain Strategy” as strategic/policy directions for de-carbonising freight transport (Ministry for the Environment, New Zealand Government, 2021).

The Ministry of Transport in its document titled “Transport Emissions: Pathways to Net Zero by 2050,” adopt the A-S-I framework to identify opportunities to reduce emissions across the transport system by addressing the four key elements of the transport system viz transport activity (number of trips and kilometres travelled), mode share (percentage share of different modes), energy intensity (quantity of fuel used per kilometre) and carbon intensity (emissions from quantity of fuel per kilometre). The Ministry has developed three themes to group together opportunities within this framework, with one of the three focussing on freight. The key focus areas for de-carbonising or greening freight transport are improving SC efficiency, optimising freight routes, equipment and vehicles, improving the efficiency of freight payloads, using data and support information sharing and collaboration, and improving resilience and reliability of less carbon intensive transport modes. While the overarching strategy is identified, it falls short of specific implementation measures, and seeks further research and work with industry for these (Ministry of Transport, New Zealand Government, 2021).

The preceding discussion considers freight transport, however, all attributes discussed have a more acute impact on construction transport primarily because of it being a major component of the construction logistics domain, the endemic fragmentation exacerbating the adverse sustainability impacts of construction transport, and the onus of managing construction logistics being on the construction industry unlike that of city logistics.

The construction industry exhibits endemic fragmentation in its operations. With transport forming a major component of construction logistics, and construction material being low-cost and high-volume in nature requiring large quantum of transport, the adverse impacts of construction transport are invariably more acute than freight transport in general. Sustainability now forming an integral dimension of construction operations, there is an urgent need for “greening” construction transport.

New Zealand exhibits certain peculiar traits, mainly due to its geographical isolation from the world inter alia geographical isolation, import dependency, small regional extent, long transits, small market/economy, non-existence of vehicle emission norms/standards etc. 93% of freight movement is by means of diesel-based freight transport, a third of it, construction related. The Climate Change objectives of 2050 make it incumbent that freight transport “greening” (or de-carbonisation) measures be put in place within the overall ambit of freight transport.

Government strategy does identify SC efficiency, transport optimisation, data/information sharing, collaboration, and legislation/regulation as de-carbonisation enablers under the A-S-I framework, however, it falls short of concrete implementation pathways, seeking further research. The requirement of research is substantiated by the ineptitude for adopting successful European and North American strategic and operational initiatives freight transport de-carbonisation, in (New Zealand) circumstances, they are not designed for.

This paper aims to bridge the implementation gap by suggesting a research framework for “greening” construction transport, limiting the scope to optimisation of the transport function, and re-design of the supply chain with specific reference to logistics, with the understanding that construction transport requires a higher intricacy and depth of analysis owing to the nature of construction logistics, and the onus of its management being on the construction industry. The results will also enable “greening” freight transport in general, since measures applicable to freight transport are expected to be a subset of those applicable to construction transport, as a consequence of the peculiarity of construction operations.