This paper describes the architecture, functionality, and field demonstration of a newly developed dedicated short-range communication (DSRC)-based vehicle-to-infrastructure communication system for improving traffic efficiency and safety in work-zone-related congestion buildup on U.S. roadways. The goal was to develop a portable system that could be easily deployed at a work-zone site to acquire and communicate important travel information, such as the start of congestion (SoC) and travel time (TT) of the driver. With this information, drivers could make informed decisions about route choice and be prepared for upcoming congestion. The system is composed of a portable roadside unit, which can engage the onboard units (OBUs) of traveling vehicles with DSRC technology to acquire necessary traffic data (speed, time, and location). With the acquired data, the roadside unit periodically estimates the SoC and the TT, which are broadcast to all vehicles in the coverage range. An OBU receiving the broadcast message calculates the distance to the SoC. The distance to the SoC and the TT are then relayed to the driver, who can make smart decisions about whether to seek an alternate route and when to expect a sudden speed reduction. Results from the field demonstration have shown that the developed system can adapt to a changing work-zone environment smoothly under various congestion patterns on the road.