The original purpose of this project was to construct a test section of a double-layer porous asphalt pavement where steel slag was used as the aggregate in the wearing course. The contents of the project also included a summary of the performance of earlier tests with steel slag as the aggregate in dense pavements in Sweden. It was also found that including an international literature review would be very useful. The literature review was not comprehensive but included the latest and most relevant findings. Among many advantages for steel slag over natural aggregates, the literature mentions durability, less rutting and dark colour. Also polished stone values and abrasion resistance are generally high. The main disadvantage is the higher mass which makes transportation from steel works to paving sites more expensive. Some of the dense Swedish steel slag pavements presented in this report have served well for long times, under moderate or high traffic volumes. The overall assessment comes out quite positive. The main subject in this report, is a test of steel slag aggregate in the top layer of a double-layer porous asphalt pavement paved in 2017 on motorway E4 in Huskvarna, in this report followed until 2023. This project started, as planned, in 2016 with laboratory studies aiming at gaining experience of designing steel slag pavements with high air voids content for durable performance, especially with traffic noise reduction in focus. This trial section was paved simultaneously when the double-layer pavement through Huskvarna had to be repaved where then the main section could serve as a control or reference section. Both the test and the control sections had an identical bottom layer while the top layer of the test section had the stone aggregate replaced by steel slag. In this way it has been possible to compare the performance of the steel slag section with a longer section of double-layer porous asphalt which is using only natural coarse aggregates.