Highway Project on forest roads

8/9/2019 Highway Project on forest roads

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Levels of Service G Through J for ADT Less Than !!"

G H # J

Flow Free flow with

adequate parking

facilities.

/eriodically

congested, such as

during peak logging

or recreational

periods.

1nterrupted by

limited passing

opportunities or

slowed by road

condition.

'low or blocked

flow. Two5way

traffic is difficult

and may require

backing to pass.

$olu%e &ncontrolled6 will

accommodate

expected traffic

volume.

"ccasionally

controlled during

heavy use periods.

7rratic6 frequently

controlled as

capacity is reached.

1ntermittent, usually

controlled, and

limited to a single

purpose.

$ehicle Types %ix of vehiclesnormally found on

public roads.

%ix of vehiclesnormally found on

public roads.

#ontrolled mix8accommodate all

vehicle types

normally found on

F' roads. 'ome

use may be

controlled by

vehicle type.

'ingle use6 notdesigned for mixed

traffic. 'ome

vehicles may not be

able to negotiate the

road.

&ritical $ehicles #learances are

adequate to allow

free travel.

"verload permitsare required.

Traffic controls

needed where

clearances are

marginal. "verload permits are required.

'pecial provisions

may be needed.

'ome vehicles will

have difficultynegotiating some

road segments.

%ay require special

temporary road

treatments, such as

filling of ditches orwater bar removal.

2oads may have to

be removed and

walked in.

Safety 'afety features are

part of the design.

'afety is a high

priority in design.

'ome protection is

accomplished by

traffic management.

/rotection may be

provided by traffic

management and

restrictions rather

than by road design.

The need for

protection is

minimized by low

speeds and traffic

management

restrictions.

Traffic

'anage%ent

ormally limited to

regulatory, warning,

and guide signs and

permits.

7mployed to reduce

traffic volume and

conflicts.

Traffic restrictions

are frequently

needed during

periods of high

volume for the

primary use.

&sed to discourage

or prohibit traffic

other than for a

single purpose.

(ser )fficiency 1mportant and high. 3enerally less ot important6 may ot a consideration.



important and may

be somewhat lower

than for level of

service 3.

be traded for lower

construction costs.

Align%ent *esign speed is the

predominant factorwithin feasible

topographical

limitations.

1nfluenced more

strongly bytopography than by

speed and efficiency.

3enerally dictated

by topographicalfeatures and

environmental

factors. *esign

speeds are generally

low.

*ictated by

topography,environmental

factors, and design

and critical vehicle

limitations. 'peed is

not important.

Road Surface 'table and smooth,

with little or no dust

during the normal

season of use.

'table for the

predominant traffic

during the normal

season of use.

/eriodic dust control

for heavy use orenvironmental

reasons.

'moothness is

commensurate with

the design speed.

%ay not be stable

under all traffic or

weather conditions

during the normal

season of use.

'urface rutting,roughness, and dust

may be present, but

are controlled for

environmental or

investment

protection.

9ough and irregular.

Travel with low5

clearance vehicles is

difficult. 'table

during dry

conditions. 9uttingand dusting

controlled for

vehicle safety, driver

visibility, and soil

and water

protection.

2ane width for forest roads like all other roads depends on the *T. !here the estimated

seasonal *T for the design life is :-- to $;-,: lane per direction should suffice. #ontrarily,if the estimated *T for the design life is greater than $;-, a double5lane road generally is

the minimum required . 'ingle5lane roads present economic and environmental advantages

by saving land and money.Thus unlike regular ')T" considerations, F' provides for

some flexibility regarding the number of lanes depending greatly on environmental factorsand expenses. The design speeds are consequently low for such roads and are generally

limited to <-mph as an absolute maximum.

"n forest roads clearances are usually the minimum allowed by ')T" and the F' designstates that it is desirable to use the minimum horizontal clearance of :.$ m for level of

service 3 and ) roads. The appropriate minimum horizontal clearance varies from - to :.$m

on level of service 1 and 4 roads, based on resident factors determined during roadorganization and design. The minimum vertical clearance on level of service 3, ), and 4

roads is (.<m. t higher speeds, consider increasing horizontal and vertical clearances.

*rainage too acts a ma0or role when considering the environmental effects it may cause. ma0or issue is where the polluted water that gets mixed with vehicle oils drain and how to

avoid having it contact natural fresh waters. . 9egarding these concerns, F' considers

relocating roads whose detrimental effects on subsurface flows cause reduction in soil

moisture or drainage of sensitive wetland habitat, also F' portrays a detailed case study withdifferent scenarios regarding drainage facilities for such roads. F' design answers questions

regarding consideration of rainfall, surface runoff, subsurface flow interception, and stream

crossings. The ultimate goal is that road drainage should simulate natural drainage patterns



and should not interfere with natural hydrological processes. ext, the Forest 'ervice must

obtain a right5of5way for road construction pro0ects that will cross private land or other lands

not under the administration of the Forest 'ervice. 2ogically, 9ight of way width shouldminimize the acquisition of forest land . Finally ,most pavement structures on F' roads are

surfaced with native soils or aggregates such as gravel, stone, slag, or volcanic cinders.

ggregates may be screened, crushed, or hauled directly from pits.

Figure 1 road cross-section

In a nutshell,the design of the FS roads has to provide a road over which the

largest trucks can maneuver ,and the driver can operate safely while also

protecting the adjacent natural resources. In our opinion, FS design criteria

should be implemented worldwide in forested areas , because it has proved to

play major role in preventing deforestation and reducing economic costs of low

volume roads.The Fs geometric road designs have been implemented on

4!!!!km of roads in the "S# up to the year $!%4.The success of this design

handbook is mainly due to the &e'ibility it provides,not by overturning the

principles of highway engineering , but by changing the emphasis of the highway

engineering components.

Highway Project on forest roads

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