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Approaches that experience blockage due to downstream conditions Approaches that operate within a well-coordinated signal system such that the majority of vehicles arrive during the green phase of the traffic signal In addition, the guidelines do not provide statistical or analytical models to predict the number of crashes or conflicts on an ATL. Rather, a summary of crash data obtained for ATL approaches is provided. Lastly, these guidelines do not provide guidance for applying ATLs relative to other capacity-enhancing intersection treatments. ORGANIZATION OF GUIDELINES These guidelines are organized to follow a typical analysis and design process for ATLs as shown in Exhibit 1-2. Also included is the corresponding chapter that documents the information and procedures needed to carry out the appropriate step in the process. The title and content for all chapters and appendices are described below: Chapter 2: ATL Characteristics. Describes the operational, safety, and design characteristics of ATLs, as well as needs and considerations for potential ATL user types. Chapter 3: Operational Analysis. Presents a statistical model for predicting the amount of traffic that will use an ATL for approaches with one or two CTLs. Chapter 4: Safety. Documents the results from an evaluation of field crash data and discusses geometric and operational factors expected to impact the safety performance of an ATL. Chapter 5: Geometric and Traffic Design. Describes an approach for preparing a functional design plan for an ATL, provides a method for determining the minimum upstream and downstream ATL length, and presents guidance on signing and pavement markings for ATLs. Chapter 6: Sample Application. Demonstrates how to apply the operations, safety and design tools, methods, and guidelines to a practical example. Appendix A. Describes how analysts can use traffic simulation models to estimate the operational performance and, to a limited extent, the safety performance of ATL designs. Appendix B. Describes the computational engine that carries out the deterministic operational analysis procedure described in Chapter 3. Appendix C. Describes the method and equations for calculating the minimum required upstream and downstream ATL lengths. Page 3

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Exhibit 1-2 Guidelines Organization Assess M ultimodal Need s I dentif y f acility needs fo r pedestrians, bicyclists, and transit r ider s ( Chapter 2) E valuate Traffic Operations HCM analysi s u s ing statistica l m odel to predic t AT L u se ( Chapter 3 & A ppendix B) Microsimulation (Appendix A) Assess Safety Effect s Q ualitativ e e v aluation ( Chapter 4) Conflic t p r ediction (Appendix A) Calculate Design Elements Upstream Passive Taper Upstream AT L Lengt h Downstream AT L Lengt h Downstream Activ e Taper ( Chapter 5) L ay Out Individual Segments A pproaching AT L A pproaching S ignal Departing Intersection Merg e a t E nd of AT L ( Chapter 5) Sample AT L F unctional Design P lan N OTE S No additional dat a r equired beyond traditional intersection analysi s A pplicable to approaches with one or tw o c ontinuous through lanes and an e xclusiv e o r s hared r ight-turn lane Page 4