Red Retroreflective Raised Pavement Markings: Driver Understanding of Their Purpose

Research was conducted to evaluate drivers’ understanding of red retroreflective raised pavement markers (RRPMs) on two-lane and four-lane undivided and divided roadways. The study included 191 participants, equally divided between three participant groups: drivers from countries with left-hand drive (e.g., Australia, United Kingdom, and Japan), drivers from Hawaii, and drivers from the continental United States. Five typical roadway configurations were tested by means of a laptop survey. For each roadway configuration, standard pavement markings were shown as a baseline condition. Three alternate marking treatments were shown for each typical roadway configuration. Two of the alternative marking treatments consisted of different combinations of supplemental RRPMs, and the third alternative treatment consisted of supplemental pavement marking arrows without RRPMs. The general findings were that red RRPMs on one-way divided roadways to indicate the wrong direction of travel helped drivers realize when they were going in the wrong direction; red RRPMs on undivided roadways can improve understanding of drivers from countries with left-hand drive without reducing the understanding of drivers from Hawaii and the continental United States; and replacing supplemental RRPMs with supplemental arrows always improved the rates of correct responses for all roadway configurations and for all participant groups.