Road damage rises steeply with axle weight, and is estimated "as a rule of thumb... for reasonably strong pavement surfaces" to be proportional to the [[fourth power]] of the axle weight.<ref>{{cite webjournal | title = Road Wear from Heavy Vehicles: An Overview | url = http://www.nvfnorden.org/lisalib/getfile.aspx?itemid=261 |page = 17+36 | format = PDF | year = 2008 | publisher = NVF committee Vehicles and Transports | first1 = Mattias | last1 = Hjort | first2 = Mattias | last2 = Haraldsson | first3 = Jan | last3 = Jansen |journal = Rapport| issn = 0347-2485 }}</ref> This means that doubling the axle weight will increase road damage (2x2x2x2)=16 times.<ref>{{cite web|url=http://www.pavementinteractive.org/article/equivalent-single-axle-load/|title=Equivalent Single Axle Load|publisher=Pavement Interactive|access-date=25 April 2012}}</ref><ref>{{cite web|url=http://www.sddot.com/transportation/trucking/docs/SDDOT_Truck_Briefing_2d.pdf|title=Truck Weights and Highways|access-date=25 April 2012|publisher=South Dakota Department of Transport}}</ref> For this reason, trucks with a high axle weight are heavily taxed in most countries.
