Introduction to Life Cycle Assessment in Infrastructure
Life cycle assessment (LCA) is a scientific method used to evaluate the environmental impacts of a product, system, or infrastructure project throughout its entire life — from the extraction of raw materials to the end of its useful life. In the context of highways and transport infrastructure, conducting an life cycle assessment is critical to understanding how design, construction, maintenance, and demolition influence sustainability, resource use, and carbon footprint.
In this blog post, we’ll walk through a detailed assessment example of a highway project. This study not only explores environmental product performance but also supports more informed decision-making around design, materials, and long-term sustainability. Whether you’re a civil engineer, policy maker, or sustainability advocate, this example provides valuable data and insights that can drive better environmental outcomes in infrastructure projects.
What is a Life Cycle Assessment (LCA)?
A life cycle assessment is a structured method used to quantify the environmental impact of products and services across their entire life cycle. Often referred to as a “cradle-to-grave” study, it involves analysing inputs and outputs associated with:
- Raw material extraction
- Manufacturing
- Transport
- Use and maintenance
- End-of-life treatment (e.g., recycling or disposal)
The aim is to capture all the energy, resources, carbon, and impacts involved, supporting better sustainability strategies. A life cycle approach is especially important in infrastructure projects due to their long service lives and significant environmental impact.
Why Conduct a Life Cycle Assessment for a Highway?
Highways are resource-intensive systems that consume vast amounts of materials, energy, and space. Their construction and maintenance have long-term impacts on ecosystems, communities, and the climate. Key motivations for conducting an example life cycle assessment on a highway include:
- Identifying stages with the highest carbon footprint
- Comparing materials and design options
- Supporting transparent, data-driven planning
- Improving sustainability and reducing waste
- Meeting regulatory and funding requirements
Such an assessment ensures that highway authorities and designers select the most environmental and economically viable solutions.
Highway Example Life Cycle Assessment: Project Overview
Project Scope
This example evaluates a 10 km dual carriageway in the United Kingdom, including embankments, pavement structure, drainage, signage, and lighting. The analysis considers a cradle-to-grave boundary with a 60-year service life.
Functional Unit
The functional unit for this cycle assessment is 1 km of operational highway over 60 years. This standardisation allows for comparisons between similar infrastructure assessment examples.
System Boundary
This life cycle assessment includes the following stages:
- Cradle to construction (materials, production, and transport)
- Construction and installation
- Use phase (maintenance, energy for lighting, etc.)
- End-of-life (decommissioning and recycling/disposal)
Life Cycle Stages and Environmental Impacts
1. Raw Materials and Manufacturing
The majority of the highway’s carbon footprint originates from the extraction and processing of raw materials like aggregate, cement, steel, and bitumen. These materials have high energy intensities and contribute significantly to total environmental impacts.
Key findings:
- Concrete production for pavements contributed 42% of total carbon emissions.
- Asphalt binder and surfacing made up 27% of impacts.
- Steel used in reinforcements and barriers accounted for 13%.
2. Construction
Construction activities involved heavy machinery and transport, contributing to fuel use and direct emissions. Dust and noise pollution also added to local environmental burdens.
Impact hotspots:
- Diesel use by construction equipment
- Material transport from production sites
- Temporary site infrastructure energy use
3. Use and Maintenance Phase
Though highways are passive products, their lighting and maintenance involve substantial energy and material use over time.
Maintenance includes resurfacing, lane repainting, barrier repair, and drainage cleaning. LED lighting has significantly reduced the carbon footprint of lighting operations.
Over 60 years:
- Maintenance contributed 15% of total carbon emissions.
- Lighting and signage operations added 8% to the total impact.
4. End-of-Life
End-of-life processes included demolition, material recovery, and waste management. Recycling rates were high due to advances in road material recovery technology.
- 70% of asphalt and concrete was reclaimed for reuse.
- Metal components were largely recyclable.
- Landfill waste accounted for only 5% of total volume.
The environmental impact of this stage was less than 5% of total life cycle impacts.
Sensitivity Analysis: Material Substitutions
To enhance sustainability, alternative materials were explored in this assessment example. Substituting Portland cement with ground granulated blast-furnace slag (GGBS) and incorporating recycled asphalt pavement (RAP) were modelled.
Findings:
- GGBS substitution reduced concrete by 34%.
- RAP usage lowered asphalt production emissions by 25%.
These substitutions demonstrate how design decisions directly influence life cycle assessment outcomes.
Interpretation and Key Findings
The example life cycle assessment of this highway project reveals:
- The cradle stage is the most carbon-intensive, driven by high-emission raw materials.
- Design choices have long-term impact across the entire life cycle.
- Maintenance contributes less than construction but is still significant.
- Material reuse and recycling dramatically lower environmental burdens at end-of-life.
The total carbon footprint for 1 km over 60 years was estimated at 14,300 tonnes CO2e.
Recommendations for Sustainable Infrastructure
Based on this assessment, several strategies are recommended to reduce environmental impacts:
- Optimise design for durability and low-maintenance
- Use locally sourced and low-carbon materials
- Implement material recycling from the start
- Invest in energy-efficient lighting systems
- Integrate assessment results into procurement and planning
Policy support and lifecycle thinking can significantly improve infrastructure sustainability.
Comparing Highway LCA to Other Assessment Examples
This example fits within a growing set of assessment examples across the transport sector. Other studies on railways and bridges show similar trends:
- Raw materials dominate carbon outputs.
- Use-phase energy matters more in electrified systems.
- End-of-life recycling varies based on materials and regulations.
Comparative life cycle assessments provide essential benchmarking data for national infrastructure planning.
The Role of Environmental Product Declarations
Environmental product declarations (EPDs) play a crucial role in life cycle assessments. They offer third-party verified data about products, enabling accurate modelling of impacts. For this study, EPDs were used for:
- Ready-mix concrete
- Bituminous mixtures
- Reinforcing steel
Using EPDs ensures precision, transparency, and comparability in cycle modelling.
Future Directions for Life Cycle Assessment in Highways
As climate targets tighten and public scrutiny increases, life cycle assessment will become a standard requirement for infrastructure delivery. Future improvements may include:
- Real-time data integration from digital twins
- AI-enhanced cycle assessment tools
- Dynamic modelling of traffic-related impacts
These developments will allow for smarter, more adaptive planning across the highway system.
Conclusion
This example life cycle assessment of a UK highway project demonstrates the power of LCA to inform better, more sustainable infrastructure decisions. By considering every phase of the life cycle, from raw material extraction to end-of-life, stakeholders can reduce the environmental impacts and carbon footprint of transport systems.
Whether you’re a designer, policymaker, contractor, or sustainability manager, understanding and applying life cycle thinking is no longer optional—it’s essential for building resilient, future-ready infrastructure.
If you’re looking to start your own life cycle assessment or explore more assessment examples, make sure your data, tools, and processes are up to date. Sustainability in highways isn’t just about the product itself—it’s about the life it lives.
