Directional sound can be used as a warning signal to communicate that failure to follow an indicated action could result in serious accidents. In some applications, such as alerting a vehicle that is likely to intrude into a highway construction work zone, long distance auditory warnings are necessary, and directed sound could be used to warn the specific vehicle without disturbing other vehicles on the highway. This study reviewed currently available scientific technologies as part of an effort to develop a long distance auditory warning system for highway work zone applications; the system would provide warning to the violating vehicle, the flag operator, and work zone crew to ensure everyone?s safety. A team of researchers worked with Mn/Dot maintenance engineers to test the developed systems in realistic workzone intrusion scenarios. Of the technologies studied, ultrasound-based parameter arrays and time-delay-controlled arrays of compact ordinary speakers were examined for detailed analysis and experimental evaluation. It was found that an ultrasound-based parametric array is the most appropriate technology for generating highly directional sound; however, if cost, installation, maintenance, and price are considered, arrays of flat-panel loudspeakers with time delay control were found to be the most suitable technology. Such a system can be used to generate directional sound effectively for long distance auditory warnings.