Attachment 2 - Design Parameters.pdf

Multi-Use Trail, Trail Assessment 12444222R0011 Sam Houston Ranger District Page 1 of 2

Design Parameters (FSH 2309.18, Section 23.22, Exhibit 01)

Design Parameters are technical guidelines for the survey, design, construction, maintenance, and assessment of National Forest System trails, based on their Designed Use and Trail Class and consistent with their management intent1. Local deviations from any Design Parameter may be established based on trail-specific conditions, topography, or other factors, provided that the deviations are consistent with the general intent of the applicable Trail Class.

Designed Use

ALL-TERRAIN VEHICLE

Trail Class 1

Trail Class 2

Trail Class 3

Trail Class 4

Trail Class 5

Design Tread Width

Single Lane Typically not designed or actively managed for ATVs, although use may be allowed

48" -60" 60" 60" - 72" Typically not designed or actively managed for ATVs, although use may be allowed Double Lane 96" 96" -108" 96" -120"

Structures (Minimum V\,1dth)

60" 60" 60"

Design Surface2

Type Native, with limited grading

May be continuously rough

Sections of soft or unstable tread on grades < 5% may be common and continuous

Native, with some onsite borrow or imported material where needed for stabilization and occasional grading

Intermittently rough

Sections of soft or unstable tread on grades < 5% may be present

Native, with imported materials for tread stabilization likely and routine grading

Minor roughness

Sections of soft tread uncommon

Protrusions s 6"

May be common and continuous

3n

May be common, but not continuous

3"

Uncommon and not continuous

Obstacles (Maximum Height)

12"

May be common or placed for increased challenge

6"

May be common and left for increased challenge

3"

Uncommon

Design Grade2

Target Grade 10%-25% 5%-15% 3%-10%

Short Pitch Maximum 35% 25% 15%

Maximum Pitch Density 20% - 40% of trail 15% - 30% of trail 10% - 20% of trail

10/16/2008

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Multi-Use Trail, Trail Assessment 12444222R0011 Sam Houston Ranger District Page 2 of 2

Designed Use

ALL-TERRAIN VEHICLE

Trail Class 1

Trail Class 2

Trail Class 3

Trail Class 4

Trail Class 5

Cross Slope

Target Cross Slope 5%-10% 3%-8% 3%-5%

Maximum Cross Slope

15%

10%

8%

Clearing

Height 6' - 7' 6'-8' 8'-10'

Width (On steep side hills, increase clearing on uphill side by 6" -12")

60"

Some light vegetation may encroach into clearing area

60"- 72" 72" - 96"

Shoulder Clearance 0"-6" 6"-12" 12"-18"

Design Turn

Radius 6'-8' 8'-10' 8'-12'

1 For definitions of Design Parameter attributes (e.g., Design Tread Width and Short Pitch Maximum) see FSH 2309.18, section 05.

2 The determination of trail-specific Design Grade, Design Surface, and other Design Parameters should be based upon soils. hydrological conditions, use levels, erosion potential, and other factors contributing to surface stability and overall sustainability of the trail.

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