A DME arc is a curved track at a constant distance around a facility that offers omnidirectional course information and DME, such as a VORTAC, VOR/DME or NDB/DME. This eliminates ILS or LOC DMEs. An arcs radius is 7- 30 NM and is 5-15 NM long, with 10 NM preferred. Thus, arcs can be lengthy and inefficient. The primary area required obstacle clearance is 1000 feet within four NM of the arc along the initial segment, with a 500-foot secondary clearance extending another two NM. In the intermediate segment, the clearance drops to 500 feet.