In this country, runway grooving has been becoming to be widely adopted to insure safer operation of large or high-speed aircraft at time of take-off or landing.
　According to the experience in some airports, there are several deteriorations of grooves such as flowing back together and wearing of their edges in asphalt pavement. The stability and durability of grooves must be large to sustain the intended functions of grooving for a long period.
　To improve the stability and durability of grooves in asphalt pavement, we made clear at first the basic characteristics of deteriorations of grooves, and investigated on what kinds of runway surface materials were more suitable for groving and how long runway surface materials had to be cured until groroving construction.
　From these investigations, the following items were indicated.
(1) The aggregate in asphalt concrete should be corser than that used up to now.
(2) Rubber-resin-asphalt is desirable for the binder in asphalt concrete.
(3) The minimum curing time of runway surface materials until grooving constrnction may be two months.