Road traffic noise may be reduced by measures directed either at the emission or at the immission. Emission control, which aims at controlling noise at the source, is usually achieved by limiting the vehicle speed, controlling emitted noise levels of the vehicles at some standard running conditions, by selecting quiet tires, or by selecting a certain road surface. Immission control, which aims at reducing the noise propagation from the source to the recipient, is generally achieved by measures such as constructing noise barriers or earth berms along the road, by planting vegetation barriers, and/or by exchanging regular windows against special sound-reducing windows. Immission-related measures are generally applied locally and are undertaken by road authorities, private companies or individuals exposed to the noise. Planning of dwelling areas and location of streets and highways, which mostly implies trying to separate them as much as possible, can also be considered a type of immission control. Vehicle and tire/road noise emission control may be undertaken on local, national or international levels. Selection of an acoustically favourable road surface is generally a local measure, but may also be national if the road authority decides to apply it at a national level. An example is the Dutch road authorities who decided several years ago to pave most of the Dutch motorways and many highways with porous asphalt surfaces. Controlling the noise level of vehicles in use is both a local measure and a national one. An example of this is the Swedish regulation of motorcycle noise emission - basically a check of exhaust systems. It is local because motorcycles are checked at a location identified by police to have a problem, but it is national since it is based on a national regulation. However, vehicle noise control of new vehicles is an international issue (like in most European countries), although some countries apply national regulations (like Japan, Australia and USA). Noise emission may be controlled also by traffic regulations, mostly by limiting speeds, time or streets when/where heavy vehicles may drive. Such regulations may be either national or local. For the covering abstract see IRRD E104312.