Left-Turn Accommodations at Unsignalized Intersections (2013) / Chapter Skim
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30 Introduction This chapter includes 11 design examples and case studies, based on actual locations at which left-turn treatments were considered, evaluated, and/or installed. These case studies include: 1.
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31 • Grades at the intersection are level. • Lane widths are 12 ft.
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32 Left-Turn Lane Peak-Hour Volume (veh/hr) Three-Leg Intersection, Major Urban and Suburban Arterial Volume (veh/hr/ln)
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Figure 15. Laurel Drive/Route 206 intersection: existing condition.
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34 Design Considerations and Analysis The primary design considerations evaluated by NJDOT included the existing traffic operations and safety characteristics of the intersection. In this particular instance, right-ofway and budgetary limitations eliminated the prospect of additional widening on Route 206, such that the addition of the left-turn lane needed to be accommodated within the existing pavement width along Route 206.
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35 Specifically, Monroe County considers roadways with the following characteristics to be good candidates for road diets: • Four travel lanes with peak directional traffic volumes that could be accommodated by one travel lane in each direction, • A record of crash patterns correctable by the implementation of left-turn lanes, • Signalized intersections that would maintain adequate capacity following the road diet conversion, • No closely spaced signals, and • Low potential for future roadside development. With respect to the characteristics above, Titus Avenue was considered for a road diet based on its cross section (four travel lanes)
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36 Context Franklin Avenue is a two-way, east-west local road located in a predominately rural area in central California. It accommodates one 12-ft travel lane in each direction, with no paved shoulder, and has a posted speed of 55 mph.
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37 deceleration lane length. It is desirable that deceleration take place entirely off the through traffic lanes.
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38 with 85th percentile speeds in the 60 to 65 mph range. Trucks account for approximately 15 percent of the vehicle mix in the traffic stream.
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39 This design application focuses on the J-turn treatment at the intersection of College Lane and US 15. In the vicinity of College Lane, US 15 bisects the campus of Mount Saint Mary's University, just south of Emmitsburg, Maryland.
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40 Context Sherwood Road is a two-way, east-west local street that provides access to a rapidly developing industrial park area that currently includes a furniture store and a major distribution center for a fast-food restaurant chain. The 1997 AADT on Sherwood Road was 1,950 vehicles per day, but daily and peakhour volumes are expected to increase significantly in the future as a result of intensifying operations for the existing industrial uses along Sherwood Road, and anticipated new developments in the industrial park.
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41 the southbound left-turn passing blister on SR 46 and other improvements. Construction of this improvement was completed in 2005.
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42 pal arterial and had a 1997 AADT of 8,400 vehicles per day, of which approximately 13 percent were commercial vehicles. US 281 has a posted speed of 55 mph and accommodates one 12-ft travel lane, plus a 4-ft shoulder, in each direction.
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43 length, deceleration lengths were not planned for the left-turn lanes due to the relatively low volume of left-turn movements and the available sight distance along this section of US 281. The storage lengths for the northbound and southbound leftturn lanes (i.e., approximately 98 ft)
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44 However, the applicant disputed the use of ITE trip generation rates, noting that the proposed surgery center would have unique operational characteristics, quite unlike the traditional medical/dental office uses reflected in the ITE database. In particular, the applicant noted that the surgery center would have: • No patient examinations, check-ups, or follow-up appointments; • No prescription refills; • No visits by nurse practitioners or other assistants; • An average patient stay of 4 hours (longer than that suggested by ITE)
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45 Figure 25 illustrates the post-development configuration of the facility's access driveways on the south side of SR 542. Design Application #9: Installation of Left-Turn Lanes at Unsignalized Intersections in Conjunction with a Proposed Development (Note: The intersection location in this design application has been made anonymous at the request of the contributing agency.
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46 lanes, thereby improving capacity, operations, and safety in the vicinity of the development. As a result, the applicant included improvement plans for a northbound left-turn lane at the Meadow Terrace/Route 52 intersection, as well as a southbound left-turn lane at the Parent Lane/Route 52 intersection.
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47 intersection is located in a primarily suburban area of Stuart. Land uses adjacent to the intersection include residential housing (single-family homes and mobile homes)
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48 resulted in damage to the east shoulder on SR 76 and created potential sideswipe conflicts with left-turning vehicles. A total of five pedestrians were observed during the course of the 8-hour count.
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49 Context Conservatory Parkway is a two-way, east-west suburban arterial that serves as a border between two adjoining cities and is part of the state highway system as Route 90. The cross section of Route 90 is one 12-ft travel lane and a 10-ft shoulder in each direction.
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50 the hospital access to provide an eastbound turning lane for the hospital, upstream of the eastbound left-turn lane for the intersection. On the westbound approach to the intersection, the DOT used the typical lengths in their design manual.
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