The main objective of this research is to develop and deploy a low-cost and scalable smart Internet of Things (IoT) proximity alert system using the IoT mobile sensing technology for alerting workers and equipment operators in proximity hazard situations in highway work zones. This research consisted of 5 field tests, including a preliminary test and 4 evaluation tests. Through the tests, the technical and practical feasibility of the system was evaluated. The experiences of the workers who participated in the tests were investigated by collecting and analyzing a questionnaire survey. With the developed system, it is expected that GDOT can improve the safety in proximity between equipment and workers by deploying the low-cost proximity alert system.