§ 1.4.2. General Design Criteria

The following criteria shall apply to streets designed to "Alternate Geometric Design Criteria":

A.

Grades. General guidelines pertaining to grades as noted in Section 1.3.1 A apply. Specific grade criteria (alternate design) for local and collector streets are noted in Figures 1-45 through 1-58 contained in Appendix H of this manual. Specific grade criteria for arterials (alternate design) are noted below in Table 1-8.

TABLE 1-8 MAXIMUM GRADES FOR ARTERIALS (ALTERNATE GEOMETRIC DESIGN CRITERIA)
Classification	Maximum Sustained Grade (%)		Maximum Grade (%)
	D>1,500′	1,500′>D>500′	D<500″
MINOR ARTERIALS
4 Ln., Undivided	9	10	11
4 Ln., Lt-Turn	9	10	11
4 Ln., Divided	9	10	11
MAJOR ARTERIALS
4 Ln., Divided	8	9	10
6 Ln., Divided	8	9	10
8 Ln., Divided	8	9	10
Source: Texas Capital Area Builders Association

 

Construction at grades of 8 percent or greater requires that a Traffic and Environmental Report, prepared by a registered professional engineer, be submitted to the Public Works Department. This report shall be provided to the Environmental Board and Urban Transportation Commission. The report should analyze and estimate the following items.

1.

Necessary ROW Widths.

2.

Level of Service,

3.

Vehicle Operating Speeds.

4.

Stopping Distance.

5.

Access to Adjacent Property.

6.

Impact to Bridge Structures, Ramps and Cross-street Intersections.

7.

Environmental Impacts which address and identify:

• Profiles for those portions of the roadway crossing slopes in excess of 15 percent.

• Cross-sections for those portions of the roadway requiring cuts and fills over four (4) feet, including proposed clearing widths. This information should also include details of any proposed waterway crossings.

• Estimation of spoil amounts and proposed spoil disposal areas.

• Erosion/sedimentation control and permanent restoration plan.

• Environmental assessment addressing the anticipated impacts of the proposed roadway. The assessment shall include a hydrogeologic and vegetation element.

Hydrogeologic Element - This element to provide general information on the topography, geology and soils of the proposed roadway alignment. Some geotechnical data may be required if significant amounts of cuts land fills are proposed. Methods of containment/stabilization for cuts and fills should also be addressed in this section. This section should also identify the location of any critical environmental features. Methods for the protection of quantity and quality of recharge to point recharge features and maintenance of the integrity of bluffs and canyon rimrocks should also be addressed.

Vegetation Element - This includes an eight (8) inch tree survey. This section should also demonstrate that the roadway alignment has preserved to the greatest extent reasonable any significant trees and vegetation on the site.

• An analysis that illustrates alternative alignments and design standards that were considered in the roadway design and how the different factors were weighted in the analysis.

8.

Economic impacts - Address economic impacts associated with options considered.

Upon review of the report, the Environmental Board and the Urban Transportation Commission will submit their recommendations to the Planning Commission.

B.

Minimum Horizontal Radii. General guidelines pertaining to minimum horizontal radii as noted in Section 1.3.1 B apply.

C.

Intersection Design. General guidelines pertaining to intersections as noted in Section 1.3.1 C apply.

D.

Tapers. General guidelines pertaining to tapers as noted in Section 1.3.1 D apply.

E.

Median and Median Breaks. General guidelines pertaining to medians and median breaks as noted in Section 1.3.1 E apply.

F.

Turn Lanes and Channelization. General guidelines pertaining to turn lanes and channelization as noted in Section 1.3.1 F apply.

G.

Curbed and Guttered Streets. General guidelines and criteria pertaining to driveways as noted in Section 5 apply.

H.

Non-Curbed and Guttered Streets.

1.

Streets constructed without standard curb and gutter shall take into account provision for fordable driveway approaches or City/County culvert crossing of open drainage systems.

2.

Driveway widths and spacing shall conform to Section 5; however, the minimum spacing of 100 feet is desired for open ditches. This will provide for mowers.

3.

Drainage carried in roadside channels shall be minimized, but, when it is required, it shall meet design criteria specified in the Drainage Criteria Manual of the City of Austin.