Street Design Manual

CHAPTER 12 ROADWAY, INTERSECTION, AND TURN LANE DESIGN

Article 12.1 Roadway Design A. Complete Roadway Improvements, in conformance with the minimum roadway design cross-sections shall be made by developments along all frontages of the property or properties involved. B. Roadway improvements may include construction, fee-in-lieu, or combination of the two, which will be determined by staff, or off-site improvements. C. When a development is required to improve roadways, the developer shall be required to install pavement markings on the surface per approved plans. D. All pavement marking plans and installation shall be in conformance with MUTCD standards and specifications. E. Consideration of GSI practices is encouraged in roadway improvement projects. Section 12.1.1 Horizontal Street Design A. Design criteria for design speed, centerline radius, reverse curve tangent distance and maximum superelevation rates for streets are summarized in Table 13 Horizontal and Vertical Alignment Design Criteria . Superelevation rates, minimum runoff lengths and methods of distribution should be in accordance with AASHTO standards and specifications. B. The minimum tangent length of an approaching intersection should be 50 feet for local access system streets. All higher system streets shall have a tangent section no less than 100 feet approaching the intersection. Tangent lengths shall be measured from the intersection of the two rights-of-way. Section 12.1.2 Vertical Street Design A. Wherever practical, streets should follow the existing contours of a site so as to avoid excessive grading and removal of existing vegetation. Street grades shall not be less than 0.75%. Standards for vertical street design are listed in Table 13 Horizontal and Vertical Alignment Design Criteria . B. At signalized intersections, the maximum grade approaching the intersection should not exceed two percent and extend a minimum distance of 200 feet in each direction measured from the outside edge of travel way of the intersecting street. C. For intersections not controlled by a traffic signal, the maximum grade approaching the intersection should not exceed five percent and extend a minimum distance of 100 feet in each direction.

Raleigh Street Design Manual – Page 84