6.1.2 Target Design Values

Table 6-1
shows target design values for Collectors for each context classification. These design values may be adjusted based on the anticipated target speed and a performance-based practical design evaluation of the corridor as discussed in
Chapter 2
.
The subsections following
Table 6-1
provide additional discussion for each design element and factors that may influence these values.
The design value thresholds for design exceptions and design waivers are presented in Appendix A and B respectively.
Table 6-1: Target Design Values for Collectors
Design Element
Rural
Rural Town
Suburban
Urban
Urban Core
Reference
Roadway
Design Speed
1
50 to 70 MPH
35 to 40 MPH
45 to 55 MPH
35 to 40 MPH
25 to 30 MPH
See 6.1.3
Travel Lane Width
12-ft
11 to 12-ft
12-ft
11-ft
11-ft
See 6.1.6
Shoulder Width (Uncurbed)
2
10-ft
2
3 to 8-ft
2
8-ft
2
3 to 8-ft
2
3 to 8-ft
2
See 6.1.7
Offset to Face of Curb
See 4.10.12
2-ft
See 4.10.12
2-ft
2-ft
See 4.10.2
Curb Parking Lane Width
5
N/A
10-ft
N/A
10-ft
10-ft
See 4.10.16
Bike Lane Width
N/A
5-ft
N/A
5-ft
5-ft
See 18.4
Speed Change Lane Width
12-ft
12-ft
12-ft
11-ft
11-ft
See 4.10.2
Median Width
See 4.10.15
Horizontal Curve Radius
See 4.7
Cross Slope on a Tangent
2%
See 4.10.4
Cross Slope on a Tangent (Maximum)
3%
See 4.10.4
Superelevation Rate
See Table 4-3 through Table 4-7
See 4.7.3
Minimum Grade (PGL)
0.25%(lined ditch channels), 0.3% (curbed facilities), or 0.5%(unpaved ditches)
See 4.8.1
Maximum Grade (Level)
4%
8%
6%
8%
9%
See 4.8.1
Maximum Grade (Rolling)
5%
9%
7%
9%
11%
See 4.8.1
Vertical Clearance at New Structures
3
16.5-ft
3
See 4.8.6
Design Loading Structural Capacity
HL-93
AASHTO LRFD Bridge Design Specs
Stopping Sight Distance (SSD)
See 4.11.1
Design Vehicle
4
WB-67
WB-67
WB-67
SU-40
4
CITY-BUS
4
See 4.3.2
Level of Service (LOS Design Year)
B
B
B
B
C
See 4.3.4.1
Roadside
Clear Zone (Curbed)
See 4.10.7
Clear Zone (Uncurbed)
See 4.10.7
Sidewalk Width
5-ft (if applicable)
5-ft
5-ft
6 to 8-ft
5 to 8-ft
See 19.3.2
Sidewalk Offset
N/A
Varies
6-ft or more for curbed roadways
Clear Zone width or more for uncurbed roadways
See 19.3.2
Border Width
N/A
20-ft
20-ft
20-ft
15-ft
See 4.10.9
Notes
Denotes that this is a design exception condition if the specified values in Appendix A are not met.
Denotes that this is a design waiver condition if the specified values in Appendix B are not met.
1
The selected Design Speed should meet the anticipated target speed of the facility during non-peak hours.
2
A 12-ft paved shoulder should be considered where the volume of truck traffic exceeds 250 DDHV. An 8-ft minimum paved shoulder should be considered for truck traffic volumes that are less than 250 and the highway is located on the Texas Highway Freight Network (THFN).
3
18.5-ft vertical clearance is required for highways on the Texas Highway Freight Network (THFN). Specific railroad company guidelines may require additional vertical clearance requirements.
4
Consider providing intersection turning radii for a WB-67 design vehicle on roadways or streets that are located on the Texas Freight Network and where high (> 10%) truck turning movements are known or expected.
5
If a bike lane is adjacent to a parking lane, the parking lane width should be increased to 12-ft to allow car doors to be open without bicyclist conflict. See Section 4.10 for additional guidance.