Click for next page ( 55


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 54
6. SAMPLE APPLICATION The purpose of this chapter is to demonstrate the application of the guidelines through a practical example. Several principles discussed previously in these guidelines are critical for the practitioner to consider throughout the ATL evaluation and design process: The ATL evaluation and design approach needs to account for the project's contextual environment as well as for applicable local, state, and federal policies, standards, and guidelines. An ATL has different operational characteristics from a CTL and should always be treated as a separate lane group, regardless of whether it is a shared lane or an exclusive lane. There is an iterative and dynamic relationship among geometric design choices, traffic operations performance, and the expected safety of an ATL. This application example guides practitioners through the steps involved with conducting an operational evaluation of the addition of an ATL on a signalized intersection approach. Volume-to-capacity ratios, average delays, levels of service, and 95th percentile queue lengths under each alternative are computed on a lane-group basis according to standard Highway Capacity Manual 2010 (2) procedures for a signalized approach. This sample application makes use of the computational engine that is described in Appendix B. Exhibit 6-1 illustrates the evaluation process. Page 55

OCR for page 54
Exhibit 6-1 Evaluation Process Assess Multimodal Needs Identify facility needs for pedestrians, bicyclists, and transit riders Evaluate Traffic Operations HCM analysis using statistical model to predict ATL Microsimulation Assess Safety Effects Qualitative evaluation Conflict prediction Calculate Design Elements Upstream Passive Taper Upstream ATL Length Downstream ATL Length Downstream Active Taper Lay Out Individual Segments Approaching ATL Approaching Signal Departing Intersection Merge at End of ATL Sample ATL Functional Design Plan NOTES No additional data required beyond traditional intersection analysis Applicable to approaches with one or two continuous through lanes and an exclusive or shared right-turn lane Page 56