Q.: While planning the offramps for an expressway the question has come up whether these can be colored to distinguish them from the regular traffic lanes. If so, can you suggest how much color to use?

A.: This is a technique that has been used successfully in a number of places. Often red pigment is used in the mix. When a three-mile stretch of First Avenue in New York City was paved in 1983, one lane was colored black to help delineate it for the exclusive use of buses. In that instance 28 pounds of carbon black pigment was used per cubic yard of concrete containing 588 pounds of cement and designed for 4000-psi strength. The concrete was supplied by a ready mixed concrete producer. We suggest you talk with such producers or with manufacturers of pigments to get their recommendations.