However, longer and heavier combinations are regularly seen on public roads; special permits are issued for special cargo. The mining company Boliden AB have a standing special permit for combinations on select routes between mines in the inland and the processing plant in Boliden, taking a load of ore. Volvo has a special permit for a , steering B-trailer-trailer combination carrying two containers to and from Gothenburg harbour and the Volvo Trucks factory, all on the island of Hisingen. Another example is the ongoing project "En Trave Till" (lit. "One more pile/stack") started in December 2008. It will allow even longer vehicles to further rationalize the logging transports. As the name of the project points out, it will be able to carry four stacks of timber, instead of the usual three. The test is limited to Norrbotten county and the European route E4 between the timber terminal in Överkalix and the sawmill in Munksund (outside Piteå). The vehicle is a long truck trailer combination with a gross weight exceeding . It is estimated that this will give a 20% lower cost and 20-25% CO2 emissions reduction compared to the regular truck combinations. As the combinations spreads its weight over more axles, braking distance, road wear and traffic safety is believed to be either the same or improved with the truck-trailer. In the same program two types of combinations will be tested in Dalsland and Bohuslän counties in western Sweden: an enhanced truck and trailer combination for use in the forest and a b-double for plain highway transportation to the mill in Skoghall. In 2012, the Northland Mining company received permission for combinations with normal axle load (an extra dolly) for use on the Kaunisvaara-Svappavaara route, carrying iron ore.