According to the modelling, it is possible to reduce emissions in the road construction projects reviewed for the report without increasing the overall costs of the projects. The report will help the City steer the planning and construction of streets and parks towards a lower-carbon future and develop the climate requirements of procurement.
Choice of materials has major impact on price and emissions
The report developed a calculation model that shows how much it costs to avoid one tonne of carbon dioxide using each method, and which combination of methods is the most cost-effective for achieving a specific target. The model examines material choices and the power sources used in machinery, such as electricity and biofuels. Some of the low-carbon options were more cost-effective than conventional solutions, and, depending on the project, emissions could have been reduced by between 9 and 48 per cent without increasing the overall costs. Lower-carbon asphalt, aggregate and concrete stood out among the most cost-effective options.
The largest reductions in emissions require costly solutions. According to the model, the maximum possible reduction was, on average, a quarter for street renovation works and around half for the construction of new roads on soft ground. However, technically suitable options must be assessed on a project-by-project basis.
The report helps to identify which choices of materials can reduce emissions most effectively and affordably as early as the planning stage. At the same time, we can see how the cost of emissions reductions rises as the target is tightened.
Soil reinforcement works increase emissions significantly
Around 80 per cent of emissions from road construction projects are generated during the manufacture of materials, primarily steel, concrete, aggregates, metals and natural stone. The differences between the projects can be explained in particular by soil reinforcement, i.e. the process of strengthening soft ground prior to construction. In projects that require soil reinforcement, emissions per square metre rose four times higher compared to other projects.
For every euro spent on construction, approximately 0.40–0.90 kilograms of carbon dioxide equivalent (kgCO₂e) were emitted during road construction, and approximately 0.27–0.59 kilograms during park construction. Carbon dioxide equivalent is a unit of measurement that describes the combined climate-warming effect of greenhouse gases produced by humans. With the help of these key figures, annual emissions from infrastructure construction can, in the future, be estimated on the basis of the budget.
The data used in the study comprised cost and emissions calculations for 19 road construction projects – comprising 58 individual streets – and 16 park projects. These projects do not represent the City’s usual annual construction programme; rather, they were selected to highlight the emissions and costs associated with different types of projects. The report was drafted by Ramboll Finland Oy.
The report, entitled ‘Helsingin kaupungin eräiden infrahankkeiden kustannus- ja päästötiedon analyysi’ (Analysis of cost and emission data of selected infrastructure projects of the City of Helsinki), has been published in the Helsingin kaupungin kaupunkiympäristön aineistoja series (2026:14).