Various details of curb design, such as curb face heights, curb return radii, etc., are discussed in this section.
E 633.1 Curb Transitions
When transitioning from one street width to another, a transitional length of 10 feet minimum and 50 feet maximum should be provided on local and residential streets. The maximum length should be used for approaching traffic and the minimum length for departing traffic. On major and secondary highways a 30-to-1 taper is desirable.
Where curbs end abruptly, curb height should transition from full height to zero inches. This transition should have a minimum curb length of 10 feet for approaching traffic and 5 feet for departing traffic.
When joining different cross-sections, 20 feet should be used when transitioning from one type of curb to another. The flow line is held constant to provide a uniform lane or street width, and the curb batter is varied in order to present a smooth, continuous curb face surface.
E 633.2 Curb Measurements of Horizontal Offsets
When using a curb with nonstandard or variable batter, the flowlines should be aligned to form a straight horizontal line on the tangent portion of the street alignment. All horizontal offset distances from variable-batter curb should be measured from the flowline. All horizontal offset distances from standard-batter curb should be measured from the top of the curb face.
E 633.3 Curb Return Radii
The standard radius for all curb returns is 25 feet. There are circumstances where variations must be allowed. However, in no case should the curb return radius be less than 15 feet (except for alleys) nor more than 35 feet. See Subsection E 652.2, Sidewalk Widths.
Curb return radii at each intersection must be considered individually. When major or secondary streets are involved, stress should be laid on the use of a curb return radius that will accommodate required turning movements.
E 633.4 Curb Face Heights
Eight inches is the standard curb height for City streets. Unless a higher curb height is required to control drainage, 6 inches may be used in residential streets in hillside areas and in short lengths of street terminating in cul-de-sacs. All curbs used for medians and traffic islands should normally be 6 inches in height.
The desirable minimum curb height is 5 inches, the maximum height is 9 inches. See Subsection E 564.11, Between Intersections. Curbs less than 5 inches in height are not effective vehicle barriers and do not offer protection to pedestrians. Curbs over 8 inches in height make crossing more difficult for pedestrians, and may also interfere with the opening of the doors of cars parked along the curb.
E 633.5 Curb Removal
Existing curb should be removed to the nearest construction joint where feasible. Where this is not feasible, it should be sawcut to a minimum depth of 1 inch in order to provide a smooth join line. If the existing curb is in poor condition at the proposed join, an additional length of curb should be removed to a point where a satisfactory join can be made.
Comments