August 2026
Street works and road works are essential. They keep the infrastructure beneath and around our streets working, maintain the highway network and deliver the services on which communities and businesses depend.
But every intervention in the street also has consequences.
There are the carbon emissions associated with materials, plant, transport and waste. But there can also be traffic congestion and delays, causing additional vehicle emissions, noise and disruption, reduced access to homes and businesses and wider impacts on communities and the places in which works take place.
Understanding those consequences, and using that evidence to make better decisions, sits at the heart of the Road to Net Zero programme.
The research behind the programme
The Little Book of the Theory of Change for Street Works and Road Works sets out the research and thinking that underpin this approach.
Produced through the Road to Net Zero programme and led by the University of Birmingham, the Little Book brings together academic research, practitioner expertise and evidence from real-world case studies to examine how street works and road works can be assessed differently.
The research began with the challenge of reducing carbon emissions from works. But it quickly identified a much broader issue: carbon emissions evaluation alone does not capture the full consequences of how works are planned and delivered.
A scheme might reduce emissions from plant or materials, for example, while still creating significant impacts elsewhere through a lengthy programme, traffic diversions and delays or disruption to local communities and businesses.
The Little Book therefore makes the case for an 'all consequences' approach, considering environmental, social and economic impacts together rather than assessing individual effects in isolation.
From least cost to lowest total consequences
This represents an important shift in thinking.
Traditionally, decisions about street works and road works have understandably focused on narrow criteria about the work itself, with the overriding consideration often being short term cost of the works.
The research asks us to look beyond the immediate works site.
Streets are complex systems. They support physical movement, the activities of businesses and communities on the ground while accommodating essential utility infrastructure beneath it. An intervention in one part of that system can create consequences elsewhere.
The question therefore becomes not simply "What is the cheapest or lowest-carbon way of carrying out these works?" but:
"How can essential works be delivered efficiently and effectively with fewest adverse impacts on society?"
That principle provides the intellectual foundation for the Road to Net Zero approach.
Turning research into practical tools
Importantly, the Little Book does not stop at theory.
It explains how the research progressed through discovery, design and delivery, moving from understanding the problem to developing practical ways of assessing it.
That work underpins the Road to Net Zero tools, including the Carbon Emissions Evaluator, which provides a consistent approach to assessing carbon emissions from street works and road works, and Impact360, which enables different delivery options to be compared across carbon and wider environmental, social and economic impacts.
The aim is not for a tool to make the decision. It is to give those planning and delivering works better evidence on which to base that decision, making previously hidden impacts and trade-offs more visible.
This becomes particularly powerful when assessment happens before works begin. Different construction methods, programme durations, traffic management arrangements and other delivery choices can be compared while there is still an opportunity to change them.
What happens when the approach is applied in practice?
The Little Book also takes the theory into the real world.
Case studies examine different street and road works and demonstrate how the tools can reveal where the greatest impacts actually occur.
One of the important findings is that perceived wisdoms encourage us to use methods which are not necessarily the things that have the greatest overall impact. Traffic management, choices and works duration, for example, can have a substantial influence on carbon emissions, disruption and wider social costs, particularly in busy urban environments. To effectively challenge practice norms we need to understand how those choices affect overall outcomes in each instance.
This evidence matters because it changes where attention can be focused when works are being planned.
Rather than simply making an existing approach incrementally more efficient, better evidence creates the opportunity to ask whether there is a better approach in the first place.
Evidence as a foundation for change
The Little Book also recognises that evidence and technology alone will not transform the sector.
For a whole-system approach to become part of everyday practice, the way impacts are understood needs to influence planning, procurement, governance and ultimately the choices made by authorities, utilities, contractors and their partners.
That is the 'theory of change' at the heart of the publication: make the full consequences of different choices visible, use that evidence to support better decisions and create the conditions in which lower-impact approaches can become normal practice.
The result is an important research foundation for Road to Net Zero and for the continuing development and application of its tools.
For anyone involved in planning, commissioning or delivering street works and road works, the Little Book provides the thinking and evidence behind a simple but important proposition: achieving net zero is not only about measuring carbon. It is about understanding the street as a whole system and making better-informed decisions about the consequences of the work we do within it.
Download The Little Book of the Theory of Change for Street Works and Road Works
