Street Design Manual

Section 12.2.1 Turn Lane Warrants Additional pavement surfaces to accommodate movements shall be required and constructed at intersections to the standards specified in Table 15 Left Turn Lane Warrants for Two-Lane Roads and Figure 4 Right Turn/Deceleration Warrants under the following conditions: 1. Left Turn Lane – Signalized Intersections a) Where fully protected left-turn phasing is provided; or, b) Where peak hour left-turn volume exceeds 100 vph; or. c) Where delay caused by left turning vehicles blocking through vehicles would reduce the operating capacity of the intersection below level service “D” (LOS-D), as defined in the latest Highway Capacity Manual . 2. Right Turn lane – Signalized Intersections An exclusive right-turn lane shall be provided where the right turning volumes exceeds 300 vph and the adjacent through lane volume also exceed vph per lane. When calculating the adjacent through lane volume, it should be assumed that all through lanes have equal volumes. 3. Left Turn Lane – Unsignalized Intersection A separate left turn lane shall be provided on a two lane roadway, depending on the percent of left turning vehicles in the advancing volume against opposing volume. For four lane roadways or greater in width, a separate left turn lane should be provided when delay caused by the left turning vehicles blocking through vehicles, would reduce operating capacity of the intersection below level of service “D” (LOS-D), as defined in the latest Highway Capacity Manual . 4. Right Turn – Deceleration Lane, Unsignalized Intersection A separate turn / deceleration lane shall be provided depending on the roadway’s single lane volume, the volume of the right turning vehicles and the posted speed of the roadway. 5. Additional Turn Lanes The City may require additional turning lanes and tapers or other improvements when it believes that the absence of such improvement will create and unsafe condition or would reduce the operating capacity of the intersection below level of service “D” (LOS-D), as defined in the latest Highway Capacity Manual .

Raleigh Street Design Manual – Page 89