Evaluation of Mobile Work Zone Alarm Systems

Maintenance of highways often involves mobile work zones for various types of low speed moving operations such as striping and sweeping. The speed differential between the moving operation and traffic, and the increasing problem of distracted driving can lead to potential collisions between approaching vehicles and the truck-mounted attenuator (TMA) protecting the mobile work zone. One potential solution to this problem involves the use of a mobile work zone alarm system. This report describes the field evaluation of two types of mobile work zone alarm devices: an Alarm Device and a Directional Audio System (DAS). Three modes of operation were tested: continuous, manual, and actuated. The components of the evaluation included sound level testing, analysis of merging distances and speeds, and observations of driving behavior. The sound level results indicated that the sound levels from both systems fall within national noise standards. All of the tested configurations increased the merging distance of vehicles except for the Alarm Actuated setup. The DAS Continuous setup also reduced vehicle merging speeds and the standard deviation of merging distance. In some instances, undesirable driving behaviors were observed for some of these configurations, but it is unclear whether these driving behaviors were due to the presence of the mobile work zone alarm device. Analysis of alarm activations indicated that factors such as horizontal curves and movement of the TMA vehicle created false alarms and false negatives. The research demonstrated that mobile work zone alarms have the potential to be an effective tool in improving safety by providing audible warnings. Further refinements to the systems, such as modifications to the alarm sound and warning message, could improve system effectiveness.