FSH 7709.56 - ROAD PRECONSTRUCTION HANDBOOK
10/85 R-1 SUPPLEMENT 1
CHAPTER 4 - DESIGN
4.3 - ALIGNMENT
4.32 - Vertical Alignment. Maximum grades should be:
Sustained adverse - 8 percent
Sustained favorable - 12 percent
Adverse less than 800 feet long - 12 percent
Favorable less than 800 feet long - 15 percent
Written approval of the Forest Supervisor of grades in excess of these limits is required. This
approval authority may be redelegated to the Forest Engineer.
When log landing options are incorporated in the road design or the road will be used as a
continuous landing, reduce maximum allowable grades to 6 percent. Reduce maximum grades by
2 percent on favorable grades and by 4 percent on adverse grades when planned activities require
the use of the road when the road is snow covered or icy.
The minimum grade on soil-aggregate surfaced roads should not be less than 2 percent to
facilitate roadway drainage.
Grade transitions into and out of vertical curves should not exceed grade change increments of 2
percent per 50-foot station, except for side slope roads that intersect and then parallel each other.
Locate and design these roads to achieve the desirable road spacing within the shortest possible
distance. If necessary, use steeper grades for short distances to achieve road separation and
optimum spacing.
4.33 - Intersections. Intersections of local roads with other forest roads with an intersecting
angle between 30 degrees and 60 degrees may be designed provided:
1. The topography is a severe limiting factor and it is not practical to relocate the
intersection;
2. Local roads are dead-end and will not have constant service;
3. The design allows sufficient sight distance to give and unobstructed view of an
approaching vehicle;
4. Appropriate warning and traffic control signs are incorporated into the project; and,
5. An analysis is made and documented in the project file considering the long-range
transportation planning together with the design criteria used to assure traffic safety.
Written approval of the Forest Supervisor is required for any intersection with an intersecting
angle less than 60 degrees. This approval authority may be redelegated to the Forest Engineer.