The 12.4 km long M31 motorway links the eastern sector of motorway M0 and the Gödöllő interchange of motorway M3. Its duty is to relieve the section of M0 ring between Csömör and Árpádföld. Due to the special traffic characteristics, the double two-lane motorway has concrete pavement – the interchanges, exit and acceleration lanes and the crossing roads are asphalt-paved. The median is 3.6 m wide. In addition, the project includes the relocation of more than 100 public utilities and the construction of 2 interchanges (on road 3 and on motorway M3), 21 structures (9 underpasses and 12 overpasses) and one rest area that can be improved into a complex rest area equipped with a petrol station. During the construction, more than 1.5 million m3 of earth was built into embankment and nearly 3 million m3 of earth was cut. The continuous maintenance of the Gödöllő-Budapest traffic was also a great challenge of the project. Regarding environment protection, in addition to the survey of game movement, we put emphasis on controlling noise and air pollution: we built noise screening walls in the vicinity of Gödöllő and planted shelter-wood on 6.2 acres.