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An eco-comparator of road variants for climate change mitigation

Variways®, the Egis eco-comparator for road project variants, is designed to assess the carbon impact of road infrastructure during construction and operating phases, by means of two indicators: greenhouse gas emissions and energy consumption. Egis offers associated services to project owners who are concerned about the environmental impacts not only of their new projects, but also their expansion and development projects, in France and abroad.


Road infrastructure, a major consumer of fossil energy resources, is the source of nearly 70% of greenhouse gas (GHG) emissions from the transport sector. In this era of energy transition, controlling GHG emissions is crucial right from the design phase, and key to providing sustainable development solutions.

Contexts and Challenges

Commitment to environmental performance requires the evaluation and control of GHG emissions and energy consumption. On the basis of current knowledge, the construction (materials manufacturing and transport) and operating (vehicle emissions) phases of road projects are known to produce 10% and 90 % of GHG emissions respectively. Keenly aware of the challenges involved, Egis has developed Variways®, a tool for evaluating a road project’s carbon impact during the construction and operating phases.


Variways® is a decision-making software that helps clients to choose the most suitable road or motorway variant. Its aim is to offer users optimised “carbon design” in terms of GHG emissions and energy consumption. From the design phase, the software provides Clients with quantitative indicators allowing them to optimise their projects and to make their choices regarding variants. The indicators take account of the initial investments related to the construction phase and of the effects induced by the operating phase. In this way, Variways® allows project owners to contribute to one of the shared goals of the European Union and the French Grenelle Environment Forum: a 20% reduction in GHG emissions by 2020 (in comparison to 1990 levels).


Variways® has interactive menus that make it easy to integrate project geometry, as well as all of the parameters needed to calculate indicators for the operating and/or construction phases. Three main sets of input data are needed to calculate the indicators for the operating phase: route geometry, anticipated traffic and vehicle speeds. For the construction phase, Variways® uses twenty geometric and environmental parameters to assess the GHG emissions resulting from earthworks and from the construction of pavements, drainage, structures, tunnels and road furniture. These elements are then coupled with information stored in the program’s data base (vehicle types, construction equipment, etc.) to calculate GHG emissions and energy consumption during a given construction phase and operating period. Variways® is also able to give results in monetary terms by assessing the estimated annual cost of a ton of carbon. The software also provides the possibility of printing out different types of output data (tables, histograms, maps) in easily understood and clearly presented formats. Variways® is the first eco-comparator for road variants to have been used on projects both in France and abroad. The “operation” section of Variways® has been certified by France’s institute for roads, streets and transport infrastructure (IDDRIM).

Link to the IDRRIM technical opinion

Construction Module Operating Module

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