July 2025
This article explores how street works and road works must adapt to help achieve the UK’s Net Zero goals while also safeguarding social, environmental and economic wellbeing. It highlights the need for a more informed and system-aware approach to subsurface engineering, where decisions are made not only for performance, but also for long-term sustainability and minimal disruption. Central to this is the development of an ‘optioneering tool’ designed to help engineers and decision-makers evaluate lower-carbon alternatives and deliver better outcomes across complex urban systems.
Understanding the Ground as an Ecosystem
When undertaking subsurface engineering, we must aim to use the ground's natural functions efficiently, effectively and with care. If we take a broad view of what constitutes ‘ecosystem services', including the use of the ground’s strength, stiffness, space and capacity to manage water flow, we can make better-informed decisions when working within street corridors.
For road works and street works, the key engineering factors to consider are the strength and stiffness of the ground, which are influenced by the ground’s stress (known as mean normal effective stress, p’) and its specific volume (v). These properties are essential to the stability of roads and the buried utilities they support, such as pipes and cables.
Urban Systems and the Impact of Street Works
Beyond the physical aspects of engineering, street works and road works also interact with wider urban systems. It is helpful to view towns and cities as complex, interconnected systems. Any street works or road works represent an intervention in these systems and should be analysed accordingly. Understanding the broader consequences of such interventions is crucial and all professionals involved in this work have a responsibility for the outcomes of their actions.
It is equally important to define the standards against which these engineering actions should be judged. While functionality is essential, we must also consider sustainability and resilience, particularly our legal obligation in the UK to achieve Net Zero. However, the transition to a lower-carbon future must also support social, environmental and economic wellbeing, and avoid causing harm in these areas. That is why the Road to Net Zero project, funded through London’s Lane Rental Funds, is developing an ‘optioneering tool’ to support better engineering decisions for roads and the shallow infrastructure below them.
Comparing Traditional and Lower-Carbon Road Works
Road works present a more straightforward case, as the impact of traditional and lower-carbon alternatives is broadly similar. The main factors to consider include the materials used, waste generated (bearing in mind, for example, that old road materials can be recycled), equipment deployed, on-site activities, and the transport of staff, materials and machinery. Many of these can be replaced with lower-carbon options, although wider issues, such as traffic disruption and its knock-on effects, will still occur regardless of method.
Street works, however, are more complex and come with a broader range of impacts. In this project, we identify four main types of street works:
1. Open-cut excavation (trenching)
2. Minimum-dig technologies (or ‘keyhole surgery’), used for minor repairs
3. Trenchless technologies
4. Robotics and automation
Currently, only the first three are widely used in practice. When deciding how to maintain, upgrade or repair buried infrastructure, engineers usually choose between trenching and trenchless approaches.
Direct Impacts of Street Works
The direct impacts of street works include the same considerations as road works: materials, waste, equipment, site activities, and transport. Excavated street material is typically treated as hazardous waste under landfill regulations, but aside from this, there are viable lower-carbon alternatives. These include electric vehicles and machinery, as well as new lower-carbon construction materials. The optioneering tool is designed to help practitioners identify and evaluate these options.
Indirect impacts of street works are also significant. These include:
• Visual and physical disruption (noise, dust, vibration)
• Potential harm to the natural environment (e.g., cutting tree roots or damaging nearby green spaces)
• Damage to nearby infrastructure, such as accidental strikes to other buried utilities, or harm to roads and surface transport infrastructure
Much of this damage stems from changes in ground conditions, specifically reduced strength and stiffness due to shifts in stress and volume. Road or lane closures can also disrupt walking, cycling and driving patterns, potentially leading to:
• Increased risk of accidents
• Delays for freight, business travel and individuals
• Unpredictable bus journey times, potentially causing people to switch to cars
• Higher emissions and poor air quality from idling vehicles
• Loss of trade for local businesses due to reduced access
• Missed or delayed appointments (e.g. for healthcare, education, interviews or childcare)
• Negative impacts on people’s health and wellbeing
Trenchless Technologies as a Lower-Impact Alternative
Trenchless methods, which usually take up less space on the carriageway, can significantly reduce these negative outcomes. Trenchless technologies include 11 types of operations for installing new infrastructure, and 25 for maintaining or upgrading existing systems. All are well-established and reliable.
By using the optioneering tool to assess all available alternatives, engineers can better understand the full range of outcomes associated with each method. This allows for more informed decision-making, ensures transparency, and helps reduce risks during delivery.
Ultimately, the optioneering tool is a core part of a wider approach to decarbonising street works and road works. This approach involves innovative business models, improved resilience, and better alignment with both formal regulations and informal systems that shape how this work is carried out.
Conclusion: A Holistic Path to Decarbonisation
Delivering street works and roadworks in a way that supports the UK’s Net Zero ambition is both a technical and ethical imperative. As this article has shown, a shift towards more sustainable methods, particularly through the use of trenchless technologies and informed decision-making tools, offers a path to reduce carbon emissions while minimising disruption to people, businesses and the environment. The optioneering tool plays a vital role in enabling professionals to make evidence-based choices, balancing performance with wider societal impact. As we look to the future, embracing a holistic, system-aware approach will be essential, not only to decarbonise infrastructure delivery, but to ensure that the benefits of progress are shared fairly and responsibly across our communities.
Article by: Professor Chris Rogers, Professor of Geotechnical Engineering and Director of the Centre for Future Infrastructure and Cities at the Department of Civil Engineering, University of Birmingham.
