Traffic Impact Assessment of Moving Work Zone Operations

Road maintenance activities involve both short-term stationary work zones and moving work zones. Moving work zones typically involve striping, sweeping, pothole filling, shoulder repairs, and other quick maintenance activities. Existing traffic analysis tools for work zone scheduling are not designed to model moving work zones. A review of existing literature showed that many of the existing studies of moving bottlenecks are theoretical in nature, limited to certain lane configurations, and restrictive in the types of mobile work zone attributes considered. This research project sought to address this gap in existing knowledge by using field data from moving work zones to develop and calibrate a traffic impact analysis tool. This objective was accomplished through the fusion of multiple sources of work zone and traffic data. Four different data sources were used: Missouri Department of Transportation (MoDOT) electronic alerts (e-alerts), probe-based travel times, data from point detectors, and field videos of moving work zones recorded from the back of a truck-mounted attenuator (TMA). A linear regression model was developed to predict traffic speed inside a moving work zone. Predictor variables in the models included historical speed, number of lanes, type of lane closure, and time of day. The simulation tool VISSIM was calibrated for moving work zones using information extracted from videos of moving work zone operations. The three recommended calibration parameters are a safety reduction factor of 0.7, a minimum look ahead distance of 500 ft, and the use of a smooth closeup option. These calibration values can be used by departments of transportation (DOTs) to model moving work zone scenarios. The operational analysis concluded that a moving work activity lasting one hour or more operates best when traffic volumes are under 1,400 veh/hr/ln, and preferably under 1,000 veh/hr/ln. Further, scheduling shorter duration moving activities on high-volume roads at multiple times (on the same day or on different days) works better than scheduling a longer duration activity. The safety analysis generated tradeoff plots between the number of conflicts and combinations of activity duration and traffic volume. A DOT can use these plots to determine, for example, if it should conduct a moving work activity for a short duration when the volume is high or for a longer duration when the volume is lower.