Quantifying the effects of interference through use of an alternative method of productivity estimation

In order to determine the expected completion time of the highway pavement projects, the Department of Transportation (DOT) needs to be able to estimate the durations of individual activities required for the projects. The estimation for the activities on the critical path is even more important when calculating total project duration, and the asphalt pavement operation is one of those activities in the highway construction schedule. The objectives of this research were to develop, evaluate, and verify an alternative method to estimate construction productivity of the asphalt pavement operation. The researcher measured various productivity parameters from four pavement research projects. Each project fell into a different category when classified by geographic feature and the pavement structure. The researcher identified various interference factors and categorized them by their types such as weather, management, and work content. The factors were further categorized by their causes and association with each sub-task. The likely magnitude of each sub-task was quantified by the number of loads affected by each factor. Then the alternative time durations of each sub-task from each project were estimated using the Timed Petri-net (TPN) simulation model developed. Finally, the durations were entered to an existing pavement process model and productivity of pavement operations was estimated. The results showed that the accuracy of the productivity estimation was improved in all four research projects from different category. The estimation method developed was verified through two other pavement projects. For the weather and management interference, the researcher used the same magnitude estimated from one of the research projects that belongs to the same project category. However, for the work content interference, the actual magnitude was calculated because this information is available before production begins. The accuracy of productivity prediction was 27% and 31% respectively from the actual productivity. The researcher also applied statistical distribution to a sub-task duration and daily shift effect, and the accuracy was significantly improved to 1% and 9% respectively of the actual productivity. By using the alternative method proposed by this research, DOT can estimate construction productivity for the pavement operation more accurately.