Kentucky (natural sandstone) rock asphalt derives its esteem as a highway surfacing material from its uniform appearance on the road, its riding characteristics, and the fact that it affords the highest protection against skidding (slipperiness) of any of the paving materials now generally available (see Appendix IV). The usual methods of handling, steaming, laying and spreading offer some of the conveniences and advantages of a ready-to-use material. Although its service history during the past 50 years has been generally favorable, there has also been a certain amount of risk involved in its use, particularly in recent years on roads sustaining heavy loadings and high volumes of traffic
