The literature study “FE 04.0335/2021/ARB – Literature Study on Sustainability in Road Construction” was carried out by the Federal Highway Research Institute (BASt) in 2021. Its aim was to extend the sustainability assessment framework that had been presented in the 2016 publication “Heft S97”. The project gathered national and international knowledge on sustainability assessment, examined existing certification systems, and interviewed experts in the field. The results were used to design a digital assessment tool that can be applied to all road‑construction measures, especially to maintenance works, and that supports both project owners and contractors in selecting the most sustainable alternatives.
The technical core of the study is a multi‑layered assessment model that follows the planning phases of road projects. Modules 2 and 3 – covering the design and detailed planning stages – are considered essential for sustainability evaluation, while Module 4c (tendering and execution) is also relevant but was addressed in a separate BASt report (FE 09.0163). The assessment can be performed on three levels: an absolute score, a relative comparison against benchmark projects, or a relative comparison of alternative variants within the same project. For the relative variant comparison, project‑specific target and limit values are used. The model assigns equal weight (25 %) to four quality dimensions: ecological, economic, socio‑cultural and functional, and technical. Each dimension is further subdivided into sub‑criteria that are also weighted, allowing a single composite score to be calculated. The process quality dimension was omitted from the final score, although it remains relevant for planning, construction, and operation phases.
The study identified several international approaches that can inform the German system. In the Netherlands, the MEAT (Method for the Evaluation of the Assessment of the Sustainability of Infrastructure Projects) integrates both monetary and qualitative aspects and is already used in practice. Norway applies Environmental Product Declarations (EPDs) for renewal and maintenance projects, focusing on CO₂ emissions during specific life‑cycle stages. The Swiss system was also examined, though it was not described in detail. These examples demonstrate that a practical, monetised assessment is feasible and that the necessary data can be collected through existing digital tools.
Based on the literature review and expert input, the project team formulated the essential features of a digital sustainability assessment tool. The tool is designed to be user‑friendly, to fit into the existing digital workflow of road‑construction projects, and to support decision makers in identifying optimisation opportunities. Contractors can use the tool to demonstrate the sustainability of their proposals, while owners can compare alternatives and make evidence‑based choices. The study also outlined the steps needed to embed the assessment into technical regulations, circular letters, and potentially into legislation, thereby creating a secure legal framework for sustainability in road construction.
Collaboration in the project involved BASt as the funding and coordinating body, with contributions from academic researchers, industry experts, and representatives of existing certification bodies. The project was conducted over the course of 2021, with the final report published in early 2022. The findings provide a solid foundation for the next phase of implementing a nationwide sustainability assessment system for road construction in Germany.