Environmental differentiation rates means that those who pollute the most also pay the most at the toll point. In rate group 1, the set rates are divided into el-car, gasoline/hybrid and diesel. In rate group 2, the set rates are divided into Euro VI-standard, Euro V or older.
If you are unsure about your vehicles environment class, you can check this by finding your vehicle in Vehicle-information on Statens vegvesen webpage.
Time and environmental differentiation rates was introduced at the toll point in Bergen on June 1. 2018.