An intersection turning movement estimation procedure based on path flow estimator Anthony Chen 1 * , Piya Chootinan 2 , Seungkyu Ryu 1 , Ming Lee 3 and Will Recker 4 1 Department of Civil and Environmental Engineering, Utah State University Logan, UT 84322-4110, USA 2 Bureau of Planning, Department of Highways, Bangkok 10400, Thailand 3 Department of Civil and Environmental Engineering, University of Alaska, Fairbanks AK 99775-5900, USA 4 Department of Civil Engineering, University of California, Irvine, CA 92697-3600, USA SUMMARY Estimation of intersection turning movements is one of the key inputs required for a variety of transportation analysis, including intersection geometric design, signal timing design, traffic impact assessment, and transportation planning. Conventional approaches that use manual techniques for estimation of turning movements are insensitive to congestion. The drawbacks of the manual techniques can be amended by integrating a network traffic model with a computation procedure capable of estimating turning movements from a set of link traffic counts and intersection turning movement counts. This study proposes using the path flow estimator, originally used to estimate path flows (hence origin–destination flows), to derive not only complete link flows, but also turning movements for the whole road network given some counts at selected roads and intersections. Two case studies using actual traffic counts are used to demonstrate the proposed intersection turning movement estimation procedure. Copyright # 2010 John Wiley & Sons, Ltd. KEY WORDS: transportation planning; network traffic model; turning movement estimation; path flow estimator 1. INTRODUCTION Network traffic models (i.e., the four-step modeling procedure) were originally developed to forecast link flows on the regional circulation network. In the past decade, with the ever-increasing availability of computer hardware and software, traffic models have been widely used by traffic engineers and regional planners. In addition, the increasing consciousness on environmental impacts has also prompted agencies to recommend the use of traffic models for the assessment of traffic impacts cumulated by continuous land use and network development on a 20–30 year horizon [1]. Traditionally, the estimation of future turning movements with a traffic model involves the application of factoring algorithms among which Furness Method [2] is the most commonly used. Regional traffic models first estimate future link volumes, in and out of an intersection, based on estimated future demands, which is in general difficult to obtain. Then, the base year turning movement counts at an intersection are multiplied by factors until the total inflows and outflows of the intersection closely match the estimated link volumes. An obvious limitation of the method is the inapplicability for intersections without existing turning counts. Although recent advanced traffic sensors (e.g., video detection) have the potential to automate such data collection processes, it is still expensive to fully instrument every intersection with sensors. In addition, the Furness method assumes that future turning movements will be proportional to their existing turning counterparts. However, this is not the case when a major change occurs in the land use pattern and transportation system. In fact, the volume on a particular movement of an intersection that is on a new ‘‘preferred’’ path may dramatically increase due to the corresponding changes of travel behavior. Another approach to incorporating turning movement estimation with a traffic model is to estimate and calibrate a baseline trip table from existing traffic counts with a special computation procedure that can reproduce turning movements at key JOURNAL OF ADVANCED TRANSPORTATION J. Adv. Transp. 2012; 46:161–176 Published online 9 November 2010 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/atr.151 *Correspondence to: Anthony Chen, Department of Civil and Environmental Engineering, Utah State University Logan, UT 84322-4110, USA. E-mail: anthony.chen@usu.edu Copyright # 2010 John Wiley & Sons, Ltd.