Division 13-10-006
Intersection Design
Sections:
13-10-006-0001 Intersection Design
13-10-006-0002 Intersection Sight Triangles, Clear View Zones
13-10-006-0001 Intersection Design
A. Intersections concerned with an arterial or collector shall be joined to provide a minimum length of tangent (at right angles to the adjoining street and measured from the curb return of the adjoining street) as follows: arterial – one hundred (100) feet, major collector – seventy-five (75) feet, minor collector – fifty (50) feet, and local – fifty (50) feet. The only exception to this is when a local street intersects a minor collector.
B. Intersections not involving arterial and major collector streets shall have a minimum intersecting angle of seventy-five (75) degrees. Where two (2) residential local streets intersect, the minimum angle shall be sixty (60) degrees.
C. Curb return radii shall be as shown in Table 13-10-011-01.
D. Distances between centerlines of adjacent intersections shall be a minimum of one hundred thirty-five (135) feet, regardless of the direction of the intersecting streets.
E. Traffic control device locations shall be shown on the construction plans. Materials and workmanship shall be approved by the City Engineer and shall be in conformance with the guidelines of the Federal Highway Administration and the Manual on Uniform Traffic Control Devices (M.U.T.C.D.) current edition. All traffic controls shall be installed by the developer prior to occupancy.
F. Monuments shall be placed at the intersection of right-of-way centerlines. Refer to Section 13-03-002-0007 for survey monuments.
G. Additional right-of-way will be required at intersections where turn lanes are required.
H. Intersection grades shall conform to City of Flagstaff Standard Engineering Details except the maximum grade on all approaches to a signalized intersection or an intersection, which is likely to be signalized in the future, shall be plus or minus two percent (2%) for a distance of three hundred (300) feet from the center of the intersection.
I. The minimum spacing of driveways to signalized and unsignalized intersections shall be according to Table 13-10-006-01. The minimum spacing shall be greater as needed to avoid the functional area of an intersection or the influence area of another driveway.
The functional area extends both upstream and downstream from the physical intersection area and includes the longitudinal limits of auxiliary lanes. The influence area associated with a driveway includes (1) the impact length (the distance back from a driveway that cars begin to be affected), (2) the perception-reaction distance, and (3) the car length. Additionally, the impact length represents the distance upstream when the brake lights of through vehicles are activated or there is a lane change due to a turning vehicle. Limited access driveways (i.e., right-in and right-out only) and driveways with right turn deceleration lanes may allow a shorter minimum spacing.
Minimum spacing shall be measured from curb return of the intersecting street to the pavement edge of the driveway.
|
Minimum Spacing of Driveways to Intersections |
|
|---|---|
|
SIGNALIZED |
|
|
Posted Speed (mph) |
Minimum Spacing to Intersection (ft) |
|
< or =30 |
230 |
|
35 |
275 |
|
40 |
320 |
|
45 |
365 |
|
UNSIGNALIZED |
|
|
30 |
115 |
|
35 |
135 |
|
40 |
155 |
|
45 |
180 |
(Ord. 2017-22, Rep&ReEn, 07/05/2017)
13-10-006-0002 Intersection Sight Triangles, Clear View Zones
All intersections of public streets with private streets, driveways, alleys, and other public streets shall be designed to provide unobstructed visibility on any leg of the intersection; including visibility for pedestrian, bicycle and vehicular traffic approaching the intersection. The clear view zones shall be determined in accordance with the criteria for intersection sight triangles in the current edition of "A Policy on Geometric Design of Highways and Streets" published by AASHTO. (Ord. 2017-22, Rep&ReEn, 07/05/2017)