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Engineering > Structures


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Structural engineers in the Forest Service play a vital role in assuring the safety and utility of our bridges, towers, tramways, and other technically complex structures.


The Forest Service manages an extensive road and trail transportation system. The road system has more than 7,500 bridges. These bridges are inspected primarily by Forest Service engineers, although some are done by State engineers or by private engineers through contracts. Forest Service standards and qualifications for bridge inspectors require formal training. They are described in Forest Service Manual 7736 and comply with 23 CFR part 650.307. The formal training is available through the National Highway Institute.

design graphic Photo of Sheeps Crossing trail bridge
Sheeps Crossing trail bridge, Sierra NF, R-5. This bridge, which was designed by the R-5 bridge group, won the American Institute of Steel Construction (AISC) design award in 1984. It was the first cable-stayed bridge built in the state of California.
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The trail system has several thousand bridges and boardwalks. Most are native log and treated timber structures, but there are also conventional steel and concrete bridges. In recent years we have also successfully installed fiberglass and composite (fiber-reinforced plastic) trail bridges. Many are simple span bridges, but others are arch, suspension, or cable-stayed structures. As a major builder and owner of trail bridges, we have developed bridge design standards that apply to all types of trails. The regional bridge engineers are familiar with these standards and must be contacted for preparation of all bridge design proposals. Standards for trail bridge inspectors and inspections are currently being developed. For more information, go to

Design authority for the forest to proceed with local design of all bridges, including acquisition of prefabricated structures, must be requested from the Regional Office (FSM 7722.04). The reason for this level of review and approval is to provide safe structures for the public and our employees by maintaining consistent design standards.

For additional information about bridge design or training visit the American Society of Civil Engineers. For information about designing with timber, visit the Guide to Wood Design Information, which also contains a list of Timber Associations.


Ropeways are ski lifts, tramways, and tows. They are most commonly found operating in the winter at ski resorts. Half of all ski areas in the United States are located on National Forests and operated under special use permits. Each year, more ski areas are open year round to serve sightseers, mountain bikers, and hikers. Some tramways are built primarily as tourist attractions not associated with ski resorts.
Forest Service engineers are responsible for monitoring the safe operation of the ropeways, under agreements with the ski area operators. Forest Service engineers cooperate with State tram boards, private engineering firms, and insurance companies to perform regular equipment inspections.

Forest Service engineers have been active participants in the establishing and developing of the American National Standards Institute safety standard for ropeways, ANSI B-77.1, which is applied to virtually every ropeway in the US.

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