Street design will be in accordance with the following criteria, subject to the approval of the city engineer. Geometric design standards not specifically included in this standard will conform to the latest A Policy on Geometric Design of Highways and Streets, published by the AASHTO.
(A) Street right-of-way requirements.
(2) Right-of-way widths in excess of the standard widths may be required in special circumstances such as when:
(a) Cut or fill slopes cannot be confined within the standard width;
(b) Minimum sight distance lines on horizontal curves are not within standards;
(c) Minimum sight distances at intersections are not within the standards; and
(d) Auxiliary lanes are to be provided.
(B) Intersections. Although all intersections share certain common elements, they are not subject to generalized treatment.
(1) Minimize conflict. To minimize conflicts and provide for anticipated traffic movements, each intersection must be evaluated with regard to its individual characteristics, and designed based on the following factors:
(a) Traffic factors such as capacities, turning movements, vehicle size and operating characteristics, vehicle speed, pedestrian movements, transit operations and accident history;
(b) Physical factors such as topography, existing conditions, channelization requirements; and
(c) Human factors such as driving habits, reaction to surprises, decision and reaction time, and natural paths of movement.
(2) Angle of intersection. A right-angle intersection provides the shortest crossing distance for intersecting traffic streams. It also provides the most favorable condition for drivers to view and judge the relative position and speed of intersecting vehicles. Where special conditions exist, intersection angles may diverge from a right angle with approval of the city engineer.
(3) Alignment and profile. Intersections occurring on horizontal or crest vertical curves are undesirable. When there is latitude in the selection of intersection locations, vertical or horizontal curvature should be avoided. A line or grade change is frequently warranted when major intersections are involved. If a curve is unavoidable, it should be as flat as site conditions permit. Where the grade of the through roadway is steep, flattening through the intersections is mandatory.
(4) Intersection sight visibility.
(a) Sight visibility triangles. Clear lines of sight will be maintained along all streets, alleys and driveways to assure the safety of motorists and pedestrians.
(b) Lines of sight. Lines of sight will not be obscured between 24 inches and 6 feet through a triangular area adjacent to a driveway, an alley or a street, where such access ways intersect with another street in a T-configuration. The sight visibility triangle, or sight triangle, consists of 3 sides that are formed by two intersecting access ways and a line connecting the two.
(C) Sight distance.
(1) Adequate sight distance shall be provided at all intersections, alleys and driveways.
(2) The determination of whether an object constitutes a sight obstruction shall consider both the horizontal and vertical alignment of both intersecting roadways, as well as the height and position of the object.
(3) The sight distance required varies according to traffic speeds on the through road. A designer shall provide the sight distance based on the latest AASHTO Policy on Geometric Design of Highways and Streets and submit it with the plans.
(D) Street slopes.
(1) Typical street cross-slope. Undivided streets should have a normal crown that is a 2-way cross-slope with the cross-section high point on the street centerline. Divided streets should have cross-slope on each pavement section. The high point of each slope on each pavement section shall occur on the edge of the pavement nearest to the median. Existing conditions may cause cross-slope requirements to vary. The nominal cross-slope is 2%, with a maximum cross-slope of 3% and a minimum cross-slope of 1%. Any deviation from the nominal cross-slope shall be approved by the city engineer.
(2) Cross-slopes in street dip sections. While dip sections are discouraged, where storm drainage runoff flows must cross the street, dip sections are needed and must be approved by the city engineer. The pavements through the dip section should have a 1-way slope (no crown), curbing and medians must not be raised, and cut-off walls shall be installed in accordance with MAG Standard Detail 552. Transitions back to normal street cross-slopes will be needed at both ends of the dip section.
(3) Existing cross-slope. See Apache Junction City Code Vol. II, § 10-3-6(D) for street widening standards.
(4) Longitudinal slope.
(a) The minimum street and gutter slope for public streets is 0.0032 feet/feet (0.32%). Special approval by the city engineer is required for slopes less than the minimum.
(b) Projects that have any area with less than the approved minimum gutter slope shall provide construction staking on the actual gutter alignment (not offset) at a spacing not to exceed 25 feet and have the grades checked by a city engineering inspector immediately preceding the concrete pour.
(c) Grade breaks and grade changes shall be clearly noted and stationed on the grading and drainage plan and the profile views.
(d) Projects with longitudinal slopes less than 0.32% shall have the gutter lines water-tested in the presence of and to the satisfaction of the city’s inspector.
(5) Vertical curves. Roadways with a longitudinal grade break or grade change of greater than 1.5% shall be required to design and construct a vertical curve along that section of roadway. Vertical curves shall be designed, at a minimum, per the most current AASHTO standards.
(6) Superelevation. Although the superelevation of roadways is discouraged, unusual circumstances may require the use of superelevation. The city engineer must approve the use and design of superelevated roadways. Roadway drainage must be considered in superelevated conditions.
(7) Undulating roadways. Roadways shall be designed to eliminate undulations. In the case where an existing paved roadway undulates, it shall be removed full width and reconstructed to a new grade acceptable to the city engineer and the entire cost paid for by the developer.
(8) Side slopes. Side slopes should be designed for functional effectiveness and ease of maintenance.
(a) For areas more than 10 feet from back of curb, slopes of 4:1 or flatter shall be provided.
(b) Steeper slopes may be approved in areas more than 30 feet from back of curb when soils are not highly susceptible to erosion, or when a cut is not more than 4 feet vertical. Cuts or fills greater than 4 feet vertically shall be approved by the city engineer.
(E) Pavement tapers.
(1) Projects are required to provide sufficient pavement tapers at all necessary locations (such as the beginning or end of a project) to properly transition traffic flow between varying widths of existing and new pavement.
(2) The pavement section for tapers shall be per these standards. See Table 10-3.1 under Apache Junction City Code Vol. II, § 10-3-5 below.
(3) Pavement tapers shall be constructed with a thickened edge per MAG Standard Detail 201, Type “B.”
(4) Taper length formulas: Taper length for merging traffic situations are calculated by the following formulas:
(a) When the design speed is 40 mph or less:
TL = WxS2
60
60
(b) When the design speed is 45 mph or greater:
TL = WxS
where:
TL = Taper length in feet
S = Design speed in miles per hour. The design speed is 5 mph over the posted speed limit.
W = Width of the offset between the edge of the travel lane and the edge of the lane after the taper.
(5) Taper length for non-merging traffic situation (such as where pavement widens with traffic) is normally 50 feet minimum. However, there may be some instances when more than 50 feet of taper may be required. The requirement for a longer taper will be determined on a case-by-case basis by the city engineer.
(6) The city engineer shall investigate the existing conditions and if determined to be substandard, the project shall sawcut and remove any existing pavement tapers when extending or installing new pavement improvements.
(Ord. passed - - )