Results obtained with the rut bar were compared with those obtained with other devices, and it was determined why the rut-bar measurements are different from field observations. Also, because it would be beneficial if the cause of the rutting could be identified from the shapes of the profiles collected by next-generation rut-bar vehicles, it was determined whether this is possible. Trenching data were collected for 10 different pavements located in Texas. Rut depths were measured with several devices before a trench was cut across the traffic lane. Careful measurement of each pavement layer was done to determine the amount of rutting in each layer. Although there may be 50 mm of rutting as measured with a straightedge, the rut bar sometimes measured no rutting. The rut bar yielded zero rut depth in 10% of cases in which ruts were deeper than 16 mm. This is mainly due to limitations of the current rut-bar setup, specifically, the sensor spacing and rut-bar length. A profile alone is still not adequate to determine the layer in which rutting occurred. Material-related problems such as bleeding yielded wide-basin rutting that appears to be base or subgrade rutting, as observed from the profile alone. The profile has been found to be inadequate for determination of the major source of rutting except when there is a clear dual-wheel rut. This is a good indication that rutting is isolated to the asphalt concrete surface layer. The sensor spacing recommended for routine data collection is 100 mm. Analysis of the data shows that this spacing is 95% accurate and capable of capturing dual-tire ruts.