Knowing the performance of intersections is of utmost importance to engineers today. It affects the development, advancement, and future economic growth status of the city or place in which the intersections are located. The performance level is inferred from the levels of service of the intersections and one common way to measure the levels of service is to estimate delays for those intersections. Therefore, the estimation of delays at intersections is a very recurrent study done by traffic engineers. Different methods of calculating delays exist. Those methods are not ideal for estimating delay for all cases. The call for better methods for estimating delays for all cases is the source of much research that led to the new method that is scheduled to be included in the Highway Capacity Manual 2010, called the Incremental Queue Accumulation (IQA) method. Since it is a new method, it needs to be studied further to assess its benefits and shortcomings. The purpose of this study is to evaluate the accuracy of the IQA method. The intersection of University Parkway and Main Street in Orem, Utah was selected as the study site. Delays were estimated for northbound and southbound approaches of that intersection using both the current methods of estimating delays in the Highway Capacity Manual 2000 (HCM 2000) and the IQA methods. For both methods, both field and model analyses were done. The data were obtained from the video recorded in the BYU Transportation Lab. The IQA analysis was done cycle by cycle for each lane, and then the weighted average was acquired to get the delay for the 15 minutes of the approach. On the other hand, the HCM 2000 analysis was performed directly for the 15 minutes of the lane group and the approach. The results were compared to determine the accuracy of the IQA method. The findings indicate that the IQA method is promising; however, the method may need to be improved for right turn movements where right turn on red is allowed. Moreover, the IQA method should be checked further to determine its sensitivity to the saturation flow rate and arrival type.



College and Department

Ira A. Fulton College of Engineering and Technology; Civil and Environmental Engineering



Date Submitted


Document Type





delays, IQA, HCM