Pavement milling (cold planing, asphalt milling, or profiling) is the process of removing at least part of the surface of a paved area such as a road, bridge, or parking lot. Milling removes anywhere from just enough thickness to level and smooth the surface to a full depth removal. There are a number of different reasons for milling a paved area instead of simply repaving over the existing surface. Purpose Recycling of the road surface is one of the main reasons for milling a road surface. Milling is widely used for pavement recycling today, where the pavement is removed and ground up to be used as the aggregate in new pavement. For asphalt surfaces the product of milling is reclaimed asphalt pavement (RAP), which can be recycled in the asphalt hot mix asphalt (pavement) by combining with new aggregate and asphalt cement (binder) or a recycling agent. This reduces the impact that resurfacing has on the environment. Milling can also remove distresses from the surface, providing a better driving experience and/or longer roadway life. Some of the issues that milling can remove include: Raveling: aggregate becoming separated from the binder and loose on the road Bleeding: the binder (asphalt) coming up to the surface of the road Rutting: formation of low spots in pavement along the direction of travel usually in the wheel path Shoving: a washboard like effect transverse to the direction of travel Ride quality: uneven road surface such as swells, bumps, sags, or depressions Damage: resulting from accidents and/or fires It can also be used to control or change the height of part or all of the road. This can be done to control heights and clearances of other road structures such as: curb reveals, manhole and catch basin heights, shoulder and guardrail heights, and overhead clearances. It can also be done to change the slope or camber of the road or for grade adjustments which can help with drainage. Specialty Specialty milling can be used to form rumble strips which are often used along highways. Using milling instead of other methods, such as rolling them in, means that the rumble strips can be added at any time after the road surface has hardened. Another example is to modify the roto-milling head to create slots in concrete slabs for the dowel bar retrofit process. The typical process is to saw cut and jackhammer out the slots for