Sec. 32-27. Street design.
A. Minimum required right-of-way widths.
1. Major arterial streets and highways. As required by the current City standards.
2. Collector streets. As required by current City standards.
3. Local streets. As required by current City standards.
a. Cul-de-sac streets in residential subdivisions shall terminate in a circular right-of-way 50 feet in radius with an improved traffic turning circle 45 feet in radius. The Department may approve an equally convenient form of space where extreme conditions justify.
b. Dead-end streets will not be approved except in locations designated by the Department as necessary for future extension in development of adjacent lands. In any case, a dead-end street serving more than four lots shall provide by easement a temporary turning circle with a 50-foot radius or other acceptable design to accomplish adequate access with an improved surface.
4. Marginal access streets (frontage roads). As required by current City standards (Phoenix Supplemental Standard Details).
5. Alleys. When alleys are provided, they shall be 16 feet wide where there is single-family residential zoning on both sides; and 20 feet wide if abutting or in multi-family zoning district or districts or in commercial and industrial zoning districts. Alley intersection and sharp changes in alignment shall be avoided, but where necessary, corners shall be mitered 15 feet on each side to permit safe vehicular movement. Dead-end alleys shall be prohibited except when necessary for future extensions. All initial partial alleys shall have a minimum width of 12 feet.
B. Grades.
1. Longitudinal grade.
a. Arterial streets. As determined by the Street Transportation Director.
b. Collector streets. Maximum of seven percent.
c. Local streets. Maximum of nine percent.
2. Concrete or asphalt streets.
a. Streets with concrete gutters:
Cross-slope desirable: 0.4 percent.
Minimum: 0.15 percent.
b. Streets without concrete gutters:
Cross-slope minimum: 0.35 percent.
3. Exceptions. Where rigid adherence to these standards causes unreasonable or unwarranted hardship in design or cost without commensurate public benefit, exceptions may be made by the Department upon review and approval of the Department’s Deputy Director.
C. Vertical curves.
1. Arterial streets. As determined by the Street Transportation Director.
2. Collector and local streets. Minimum length, 100 feet, except in cases approved by Department’s Deputy Director.
D. Horizontal alignment.
1. Arterial routes. As determined by Street Transportation Director.
2. When tangent centerlines deflect from each other more than ten degrees and less than 75 degrees, or greater than 105 degrees, they shall be connected by a curve with a minimum centerline radius of 500 feet for collector streets, or 100 feet for local streets.
3. Between reverse curves there shall be a tangent section of centerline not less than 100 feet long.
4. Streets intersecting an arterial route shall do so at a 90-degree angle; intersections of local streets shall not vary from 90 degrees by more than 15 degrees.
5. Residential and collector street jogs with centerline offsets of less than 125 feet shall be avoided except under special circumstances. Minimum 350-foot centerline offsets are to be provided along major streets where left turn storage will conflict with existing intersections.
6. Local streets intersecting a collector street or arterial route shall have a tangent section of centerline at least 150 feet in length measured from the right-of-way line of the major street; except that no such tangent is required when the local street curve has a centerline radius greater than 400 feet with the center located on the major street right-of-way line. Where topographic conditions make necessary other treatment to secure the best overall design, these standards may be relaxed by the Department.
7. Street intersections with more than four legs and Y-type intersections where legs meet at acute angles shall be avoided.
8. At residential street intersections, property line corners shall be rounded by circular arc, said arc having a minimum tangent length of 12 feet.
9. The Subdivision Committee may modify the requirements of this section where there exist extraordinary conditions of topography, land ownership, adjacent development or other circumstances not provided for in these regulations. (Ord. No. G-3588, § 2; Ord. No. G-5707, 2012)