Attachment 2 - Design Parameters.pdf

Design Parameters

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 BICYCLE Trail Class 1 Trail Class 2 Trail Class 3 Trail Class 4 Trail Class 5 Design Tread Width

Single Lane 6” – 12”

12” – 24” 18” – 36” 24” – 48” 36” – 60”

Double Lane 36” – 48”

36” – 48” 36” – 48” 48” – 84” 72” – 120”

Structures (Minimum Width)

18” 18” 36” 48” 60”

Design Surface2

Type Native, un-graded

May be continuously rough

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

Native, limited grading

May be continuously rough

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

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

Intermittently rough

Sections of soft or unstable tread on grades < 5% may be present, but not common

Native, routine grading with improved sections of borrow or imported materials

Stable with minor roughness

Likely imported material, routine grading

Uniform, firm, and stable

Protrusions ≤ 24” Likely common and continuous

≤ 6” May be common and continuous

≤ 3” May be common, not continuous

≤ 3” Uncommon, not continuous

No protrusions

Obstacles (Maximum Height)

24”

12” 10” 8” No obstacles

Design Grade 2

Target Grade 5% – 20%

5% – 12% 3% – 10% 2% – 8% 2% – 5%

Short Pitch Maximum

30% 50% on downhill-only segments

25% 35% on downhill-only segments

15% 10% 8%

Maximum Pitch Density 20% – 30% of trail

10% – 30% of trail 10% – 20% of trail 5% – 10% of trail 0% – 5% of trail

10/16/2008

Designed Use BICYCLE Trail Class 1 Trail Class 2 Trail Class 3 Trail Class 4 Trail Class 5 Design Cross Slope

Target Cross Slope 5% – 10%

5% – 8% 3% – 8% 3% – 5% 2% – 3%

Maximum Cross Slope 10%

10% 8% 5% 5%

Clearing

Height 6’

6’ – 8’ 8’ 8’ - 9’ 8’ - 9’

Width 24” – 36” Some vegetation may encroach into clearing area

36” – 48” Some light vegetation may encroach into clearing area

60” – 72”

72” – 96”

Shoulder Clearance 0’ – 12”

6” – 12” 6” – 12” 6” – 18” 12” – 18”

Turn

Radius 2’ – 3’

3’ – 6’

4’ – 8’

8’ – 10’ 8’ - 12’

Design Parameters

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.

PACK AND SADDLE

Trail Class 1 Trail Class 2

Trail Class 3 Trail Class 4 Trail Class 5

Design Tread Width

Wilderness (Single Lane)

Typically not designed or actively managed for equestrians, although use may be accepted

12” – 18” May be up to 48” along steep side slopes 48” – 60” or greater along precipices

18” – 24” May be up to 48” along steep side slopes 48” – 60” or greater along precipices

24” May be up to 48” along steep side slopes 48” – 60” or greater along precipices

Typically not designed or actively managed for equestrians, although use may be accepted

Non- Wilderness (Single Lane)

12” – 24” May be up to 48” along steep side slopes 48” – 60” or greater along precipices

18” – 48” 48” – 60” or greater along precipices

24” – 96” 48” – 60” or greater along precipices

Non- Wilderness (Double Lane)

60” 60” – 84” 84” – 120”

Structures (Minimum Width)

Other than -bridges:

36” Bridges without handrails: 60” Bridges with handrails: 84” clear width

Other than bridges: 36” Bridges without handrails: 60” Bridges with handrails: 84” clear width

Other than bridges: 36” Bridges without handrails: 60” Bridges with handrails: 84” clear width

Trail Class 1 Trail Class 2

Trail Class 3 Trail Class 4 Trail Class 5

Design Surface2

Type Native, limited grading

May be frequently rough

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

Intermittently rough

Native, with improved sections of borrow or imported material, routine grading

Minor roughness

Protrusions ≤ 6” May be common and continuous

≤ 3” May be common, not continuous

≤ 3” Uncommon, not continuous

Obstacles (Maximum Height)

12”

6” 3”

10/16/2008

Trail Class

Trail Class

2 Trail Class 3 Trail Class 4 Trail Class 5 Design Grade

Target Grade 5% – 20%

3% – 12% 2% – 10%

Short Pitch Maximum

30% 20% 15%

Maximum Pitch Density 15% – 20% of trail

5% – 15% of trail 5% – 10% of trail

Design Cross Slope

Target Cross Slope 5% – 10%

3% – 5% 0% – 5%

Maximum Cross Slope 10%

8% 5%

Clearing

Height 8’ – 10’

10’

10’ – 12’

Width 72” Some light vegetation may encroach into clearing area

96”

Shoulder Clearance 6” – 12” Pack clearance:

36” x 36”

12” – 18” Pack clearance: 36” x 36”

12” – 18” Pack clearance: 36” x 36”

Design Turn Radius 4’ – 5’

5’ – 8’ 6’ – 10’

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 grades, 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.