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TECHNICAL PAPER #45
Joe Barcomb & David K. Blythe
Jonathan Kibee & Henry Parker
1600 Wilson Boulevard, Suite 500
Arlington, Virginia 22209 USA
Tel: 703/276-1800 . Fax: 703/243-1865
Understanding Low-Cost Road Building
[C]1986, Volunteers in Technical Assistance
This paper is one of a series published by Volunteers in
Technical Assistance to provide an introudction to specific
state-of-the-art technologies of intrest to people in
papers are intended to be used as guidelines to
help people chooe technologies that are suitable to their
situations. They are
not intended to provide construction or
People are urged to contact VITA or a
similar organization for further information and technical
assistance if they find that a particular technology seems
meet their needs.
The papers in the series were written, reviewed, and
almost entirely by VITA Volunteer technical experts on a
Some 500 volunteers were involved in the
production of the first 100 titles issued, contributing
approximately 5,000 hours of their time.
VITA staff included
Patrice Matthews handling typesetting and layout, and
Crouch as editor and project manager.
Joe Barcomb is a VITA Volunteer who is a civil engineer with
U.S. Forest Service.
His co-author VITA Volunteer David K.
Blythe, is a civil engineer and Associate Dean for
Education for the Department of Engineering, University of
Kentucky in Lexington.
The reviewers are also VITA Volunteers.
Jonathan Kibbee is a lawyer with Lord, Day and Lord in New
City who has worked in Haiti on a water control and
project. Henry W.
parker, retired professor emeritus of civil
engineering at Stanford University, has had extensive road
construction experience in Colombia and Venezuela.
were done by VITA Volunteer Rick Jali.
VITA is a private, nonprofit organization that supports
working on technical problems in developing countries.
offers information and assistance aimed at helping
and groups to select and implement technologies appropriate
VITA maintains an international Inquiry
Service, a specialized documentation center, and a
roster of volunteer technical consultants; manages long-term
field projects; and published a variety of technical manuals
UNDERSTANDING LOW-COST ROAD BUILDING
Volunteers Joe Barcomb and David K. Blythe
Roads vary from trails to major hard-surface highways.
on the local climate and materials available for
roads may sometimes be open to traffic for only part of the
A year-round road is often more expensive to build, and may
always be necessary.
As a general rule, road construction in
rural areas can be done at relatively low cost because,
to city roads, fewer people and vehicles travel on rural
However, rural roads must be well designed, properly
and continually maintained.
I. QUESTIONS TO CONSIDER BEFORE BUILDING A ROAD
Before you begin to make decisions about designing,
improving a road or trail system, you should consider the
1. Why do people
want a road? Do they want to take produce or
products to market? Do they want access to
assistance or other advanced technologies? Is a trail
adequate to move
people, goods, or animals, or is a full-scale
Whenever possible, try to get the local
in the design and construction of the road or
People will usually want to help build what
is needed, and
people who have participated in the construction
of roads or
trails are likely to want to maintain them.
If, on the other
hand, you are not responsive to people's
needs, they are
not likely to provide you with much help.
2. Where does the
road need to go? Determine the route that best
users, getting them from their starting point to
destination. If some intermediate
points can be
reached by going
only slightly out of the way, then try to
also. Destination points are usually
villages or better
3. How much of the
year is the road used and how heavily is it
used? A road
that is open year-round is often desirable but
expensive to construct than one open only part of
Whether this extra cost is justified will
part on how much
of the year the less expensive road would be
For example, if a road crosses a riverbed
water in it only
three weeks out of the year, is it worthwhile
to build a
bridge? Generally speaking, the more traffic
a road system
carries, the more time and money may be spent
4. What kinds of
goods need to be moved? Are they self-propelled
(like trucks or
cattle) or stationary (like bulk rice)? Are
they small or
bulky? You do not need the same type of road to
jewelry as to transport grain. The
jewelry could be
carried by a
mule on a seasonal trail, while the grain might
require a road
that was passable by truck under a variety of
conditions. Animals can be herded along
a trail or
road, but logs
might require a truck road.
5. How do people
currently travel and move their goods? Will
there be a shift
in the type of products coming from the
outside world or
from the local source? If not, then you
making limited improvements to the present
example, or a seasonal road into a year-round road.
Improving a road
or trail system significantly may not be
especially if the local people do not have the
vehicles or the
operating skills to take advantage of a more
6. What kinds of
vehicles are available to move people and
motorized vehicles used? If so, what size are
they? If for
example, motorbikes with a sidecar are the only
vehicles used, a
road with wide lanes is unnecessary.
and small trucks
need a wider road than do animal-drawn
And an animal carrying a load on its back
may not need
a road at all.
7. What is the
physical terrain? Plan to use the terrain to your
advantage. Building roads on side
slopes of 15 to 45
minimizes construction costs.
roads on steep
terrain usually means higher construction
of the high volume of earth and rock that must
be dug out and
removed. Extremely flat ground also
construction costs, because measures must be
taken to prevent
floods and washouts. Rivers and streams
avoided where possible since they may be costly to
It is also wise to avoid other obstacles
such as rock
ledges, highly erosive soils, and swampy places,
since they are
apt to create difficulties in construction.
8. What technical
skills are available? Are there personnel who
have worked on
similar projects in this or other areas who
can form a
cadre? Sources of external funding can often also
9. What equipment
is available? Do you have power-driven equipment
or are you
limited to hand tools or animal-driven equipment?
existing tools and methods be adapted to the
10. What financing
is available? Is there some form of local
can raise the funds for building or improving
the road system?
If not, are funds available from other
much money can be raised from all sources? Will
funds from all sources meet the needs of the
project, or will
the project have to be scaled down? Sometimes
organizations will donate funds equal to the
value of local
donations of labor.
11. What permissions
will be required? Will you need written
cross land owned by other people, and will you
need to secure
any permits for public road access? You might
need to get a
right-of-way to change the course of a road, to
widen it, or to
block the flow of a stream. Such
obtained before construction begins, to avoid
12. How will the
road system be maintained after it is completed?
personnel are to maintain it, do they have a vested
doing so, or are they likely to let the road fall
into such a
state of disrepair that it will have to be rebuilt?
Remember, if you
build a system that does not meet
you can expect little commitment on their
maintaining the system.
II. PLOTTING THE COURSE
Before construction begins, the proposed road or trail
is plotted or sketched on paper.
The next step is to walk the
entire length of the proposed route to become familiar with
topography and ground conditions.
The proposed route is then
surveyed to measure its slope (also called its grade or
at a number of points along its course.
If the slope between the
starting point of the survey and the next point along the
is too steep, the surveyor adjusts the route uphill or
until the desired grade is obtained.
The two points are then tied
in with markers.
This process is repeated until the entire course
is marked. The
marked line represents the center line of the
Marking can be done with blazes (spots or marks
made on trees), paint, strips of cloth, or weatherproof
tape fastened to trees.
Allowances should be made for occasional turnouts to provide
space for passing or parking vehicles.
Any curves or switchbacks
should be of sufficient radius to be negotiated easily by
largest vehicles likely to use the road.
As construction progresses,
a series of grade stakes or pegs are placed along the center
line of the road.
Two more or less parallel series of slope
stakes or pegs are then placed to mark the sides of the
Section III, Tools and Equipment, for more information about
maintaining grade and slope.
Measurment of Gradients
The steepness of a hill is usually expressed as the ratio
the height climbed and the horizontal distance covered.
example, you are climbing a hill and walk forward 100
find then that you are 10 meters higher than when you began
moving. This means
that for each 10 meters you have moved forward,
you have also moved one meter upward.
In that case, we say
that the hill you are climbing has a slope of 1 in 10.
The main point that a road builder must always remember is
roadway should not be built with a slope steeper than 1 in
Once in a great while, it may be necessary f or a road to be
steep as 1 in 7 f or a very few meters.
This is an exceptional
case, and a steeper gradient would make the entire road
It is best never to accept a trace road plan showing a
greater that 1 in 10.
You can convert a gradient expressed in degrees into a
expressed as a proportion by using the following formula, in
which 60 is a constant:
gradient as a proportion
angle of gradient in degrees
For example, suppose that we have a gradient of
5[degrees]. We use the
formula to find out how to express this gradient as a
gradient as a
proportion = 60
= 12 gradient = 1 in 12
The same formula can be reversed to give us the gradient in
degrees when we know the gradient as a proportion:
angle of gradient
in degrees = -----------------------
gradient as a proportion
Remember that the gradient of a road should not be steeper
in 10. That means
that it should not be steeper than 6[degrees].
III. TOOLS AND EQUIPMENT
Tools for Finding the Grade
Equipment for building low-cost roads can very simple.
and other large machinery may be nice, but they are costly
operate and difficult to keep in repair without access to a
skilled mechanic and expensive spare parts.
It is important,
however, that the basic equipment be used to maintain the
grade and slope. The
most basic of these tools can be built by a
reasonably skilled carpenter.
The Grading Stick
A grading stick can be used to establish a gradient of not
than 1 in 10. A
grading stick is about five feet long with 6-inch
bracket attached to one end so that the stick is ten times
as long as the bracket.
The slope that runs from the end of the
stick to the bottom of the bracket is a gradient of 1 in 10.
The grading stick is used for placing the grade stakes or
that the gradient is not steeper than 1 in 10.
The bracket of
the grading stick is placed on the peg that is further down
slope; the end of the stick is placed on the peg that is
up. A spirit level
is then laid on the grading stick. The
can now be raised or lowered until the stick is level.
is, you know that the gradient is exactly 1 in 10.
The Abney Level
The Abney level is a more complicated and accurate
than the grading stick for finding the steepness of a
gradient. <see figure 1>
The Abney level is made up of three parts:
(1) A tube about six
inches long, with an eyepiece at one end and at the other end
thin wire that horizontally divides the opening; (2) An arm
mounted above the tube, which can be moved along a scale
in degrees; (3) A small spirit level, coupled to the arm.
This level is reflected in a mirror set inside the
tube. In the
eyepiece you can see through the tube to the land beyond,
appears cut horizontally by the thin wire.
You see the small
mirror to the right of this.
If you move the spirit level slowly,
you can see the reflection of the level's bubble as it
The Abney level is best used along with a target and
target consists of a piece of wood a foot square mounted at
top of a wooden upright about 4 feet high.
The top half of the
square is painted white and the bottom half black.
The stick is
an ordinary piece of timber cut so that its height is
height of the point when the white half of the target
The level is placed on the stick.
The target is taken to the
place where the gradient needs to be determined.
To use the
level you look through the eyepiece and adjust the wire
is exactly in line with the center of the target.
You then move
the spirit level until the bubble comes in line with the
of the target. The
angle in degrees can then be read off the
It is much quicker to use an Abney level than a grading
find a trace up a hillside, because with a grading stick,
have to be put in and checked at five-foot intervals.
Abney level, the surveyor can walk along a likely trace and
simply check, when the ground seems to be rising too
that the slope is not greater than 1 in 10 (i.e., that the
of incline is not greater than 6[degrees]).
Boning rods are used to set the pegs that mark the center of
road, and ensure that the pegs lie in the same plane.
of a road or bush path built without the help of boning rods
many small dips and bumps, reflecting the shape of the
under the road. Boning
rods help assure that the surface of the
road will be level. <see figure 2>
Boning rods are made of ordinary timber one inch thick.
always come in sets of three.
All three boning rods in a set must
be identical. For
this reason, if one of the rods wears down or
breaks, it must immediately be discarded and a new rod made
replace it. A boning
rod is T-shaped; the height of the upright
of the T is 48 inches, and the length of the crosspiece is
inches. The two arms
are at right angles to each other, and must
be fastened together securely with three screwnails.
To use the
boning rods, you put them on the first two pegs and then
along the rods to place the third rod correctly.
If the crosspiece
of the third boning rod sticks up above the level of the
nearer two, then you must drive the peg on which it stands
down. If, on the
other hand, the third crosspiece cannot be
seen, the peg is too low and must be made higher.
When you have
adjusted all three pegs in this manner, so that they are all
line, the person carrying each rod moves forward so that the
next peg can be boned in (adjusted to the same level) in the
way the others were.
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The overseer of a road-building project has to decide where
road will change levels.
In flat country, it may be possible for
the road to remain at the same level for distances of about
yards, but in hilly country the level may need to be
often as every five yards.
Unless major obstacles like swamps and
mountains are unavoidable, you will probably want to select
roadway that does not require adjustments in level of more
three feet. It is
also desirable that the amount of earth that
needs to be excavated (or cut) be the same as the amount of
that needs to be used as fill.
Camber rods are used to find the side to side slope, or
of the road. Like
boning rods, camber rods are made of one-inch
timber. They are
usually eight feet long and have a bracket
attached to one end of the rod, at a right angle to the
bracket, which is attached to the rod by three screwnails,
three inches below the rest of the rod.
Camber rods are
usually used in pairs, in conjunction with a spirit level.
<see figure 3>
The pegs marking the center line of the road are "boned
the boning rods.
Behind the crew that bones in these center pegs
is a second crew that uses the camber rods to lay out the
of the road. The
camber rod is put on the center peg,
with the long rod at right angles to the center of the road,
facing so that the bracket is on the outside.
The bracket is then
rested on a peg that will mark the edge of the roadway.
is driven into the ground until the spirit level shows the
rod has become level.
The three essential things to remember are:
1. The bracket always goes on the outside.
(there is one
The three essential things to remember are:
1. The bracket
always goes on the outside. (there is
is explained on the next page.)
2. The camber rod
must always be at right angles to the center
line of the road.
3. The center peg
must never be altered. Only the outside
or camber peg,
may be adjusted to make the rod level.
the camber peg on
one side of the road has been adjusted,
then the rod
should be used to adjust the peg on the other
At this point, what you have is a line of pegs running down
center of the road and, parallel to this line of center
lines of camber pegs, one on either side of the road.
pegs are three inches lower than the center pegs, so that
sides of the road will be lower than the center.
This slope is
called the camber.
It allows water to flow off the surface of
the road into ditches running along the sides of the
road. On a
gravel or dirt road, a crown of 1/2 to 3/4 inch per foot
both ways from the center line) is adequate.
The camber pegs are joined with a string.
Then the crew making
the road can set to work.
First, they need to cut and fill around
the pegs. Then they
tamp or level the ground by moving a board
(or anything else with a straight edge) between the
dig a ditch on either side of the road, just outside the
pegs. The slope of
the sides of each ditch should be about 1:4 (1
meter of rise for every 4 meters of run), to prevent
Earth removed in digging these ditches can be used to build
The one exception to the rule that the bracket of the camber
always goes on the camber peg occurs when a road curves so
its surface needs to be banked.
If, for example, a road curves
sharply to the left, a vehicle coming around the curve tends
skid toward the right-hand ditch.
To help prevent this, the
right-hand half of the carriageway is built up higher than
center. To bank the
road in this manner, the camber rod is used
in the normal way to set the camber on the inside (the left
in our example) of the curve.
To set the opposite camber peg,
the bracket is put on the center peg, with the flat end of
rod on the outside peg.
The result is that the outside peg is
higher than the center peg, and the center peg is in turn
than the inside one.
This is the only exception to the rule that
the bracket always goes on the camber peg.
And even in this
exception, the bracket goes on the center peg only when the
on the outside of the curve is being set.
Several pieces of equipment should be mentioned in passing
they are so basic; hoes and machetes, headpans,
and measuring tapes.
A headpan is a large pan, similar in shape to a dish
carry it on their heads to transport earth or other loose
It has the advantage of being simple and durable, and
usable even over rough terrain.
When the terrain is smooth, a
headpan is a relatively inefficient carrying device, since
takes about 40 headpans of sand or earth to make up a cubic
Under most conditions, and especially over long distances, a
wheelbarrow is a more efficient carrying device than a
because of its greater capacity.
A wheelbarrow can hold about
seven times what a headpan can, but does require some
The wheel axle needs to be oiled and the tire needs to be
pumped to the proper pressure on a rubber-tired wheelbarrow.
Without correct maintenance, the wheelbarrow is likely to
The Measuring Tape
A measuring tape is made of flexible metal or of linen
usually between 50 and 100 inches long.
The linen is preferred to
the metal because it costs less and lasts longer.
It is necessary
to clean and lightly oil the metal kind from time to time;
it will rust.
IV. DRAINAGE AND SLOPE STABILIZATION
A very experienced engineer was once asked, "What are
difficult problems encountered in road construction?"
answered, "Water, water, and water."
Heavy rains can trigger floods, washouts, and
amounts of water can turn roads into puddles, ruts, and
Provisions must be made for adequate drainage if roads and
trails are to remain in serviceable condition.
In places where
floods are an annual occurrence, it may be necessary to
bridges to keep the roads and trails usable year-round.
areas and places with high ground water, ditches and
are needed to carry the water away from the road or trail
Too much water makes fine-grained soils soft and unable to
support traffic. Too
little water makes soils lose strength:
fine-grained material is either blown away or pushed to the
Where the slope is near zero percent, the best way to handle
water is to build up the trail or road area with earth, so
it is higher than the surrounding area.
In this case, every so
often there needs to be a means for water to get from one
the raised roadway to the other.
Culverts, bridges, or fords can
serve this purpose.
A culvert is a conduit or pipe under a road
or structure that permits the passage of traffic over
ford is a point where a road can cross a stream or river
there is little or no water there much of the year, and
the underlying soils can bear the weight of traffic.
A seep spring, or high water table will cause soft spots in
road. To solve this
problem, you must remove the wet material
and replace it with a suitable drainage structure.
One way to do
this is to remove the wet material and leave a trench
from the inside downward toward the outside of the
the trench with rock, starting with coarse rock at the
and progressing to fine rock as you move upward.
The top of this
filling should come to within a foot of the finished
cover this porous material with a suitable base material,
On hilly or mountainous ground, the road or trail should
some grade built into its longitudinal axis.
If the road has a
ditch, the water collecting in the ditch will need to pass
or under the road.
Water should not be allowed to run down a
ditch or along the surface of a road or trail for any
that allows the water to pick up speed.
The steeper the grade,
the faster the water travels.
The faster the water travels, the
more capacity it has to carry soil and erode the surface of
ditch or road. Water
must be removed more frequently as the grade
One of the most common methods of drainage is the
can be used to divert the flow of water in a
natural stream, or they can be used to help control run off
that accumulates in the ditches.
Culverts can be made of lumber,
logs, concrete, steel, aluminum, or clay.
You should be sure
that the material you choose makes the culvert as durable
easy to install as possible, and that it will be able to
the loads that the road will be carrying.
If a metal or concrete
culvert is going to be carrying acid water, it should be
with vitrified clay or asphalt.
If you can, install the culvert in the natural drainage
and on the same grade as the stream. The inlet for a culvert
should be at or below the level of the stream bed, not above
Avoid filling under a culvert to bring it up to grade. Lay
culvert on solid ground and pack the earth firmly at least
up the side of the pipe so that water will not leak around
it. The culvert needs adequate cover: a minimum of one foot,
half of the diameter of the culvert, whichever is greater. If
is not possible to cover the culvert adequately, then you
install two smaller culverts or a pipe arch. The cover needs
be compacted to keep the road from settling. If there is a
problem with erosion at the inlet end of the culvert, then
need to install a headwall. It can be made of such materials
logs, concrete, or hand-placed riprap.
A culvert is usually made to run along a 2 to 4 percent
that it will not become clogged. You can use an Abney level
check the grade. The flow velocity of the water that runs
the culvert should be greater than 2.5 feet per second to
sedimentation but less than 8 feet per second to prevent
Generally speaking, a 2 percent grade will give you water
velocities within this range. The outlet end of the culvert
should be at or below the toe of the fill, and there should
apron of rock for the outflow to spill onto.
When there is no time to make an exact calculation, you can
a hasty estimate of the cross-sectional area needed for a
by doubling the channel area. This gives you just a rough
since it does not take into account the shape, size,
or slope of the area, or the surface vegetation, soil
or rainfall intensity. YOu can make a more exact calculation
the cross-sectional area needed for a culvert by adding the
widths of the ditch at the top (a) and at the bottom (b),
then multiplying them by its height (H):
The result should be roughly equal to double the
area of the channel.
There are two kinds of relief culverts:
and open-top culverts.
Ditch-relief Culverts. Ditch relief culverts are put in to
water under the road before it acquires enough volume and
to cause erosion to the ditch. The culverts should be spaced
to 300 feet apart on an 8 to 10 percent grade and about 500
apart on a 5-percent grade. There will be local variations
these figures depending on the width of the road, the type
soil, and the amount of rainfall. Ditch-relief culverts
cross the road at an angle of about 30 degrees (culvert
downgrade about half the road width) to provide good
conditions on steep slopes.
Open-top Culverts. Open-top culverts are used to remove
from the surface of the road. The initial cost is low, but
kind of culvert is hard to keep clean, must be installed and
bedded with care, and may break up under heavy traffic.
culverts should be installed every 300-800 feet on roads
percent grades and 200-300 feet where the grade is 6-10
DIPS AND WATER BARS
Dips and water bars are structures that help keep water from
accumulating on the roadways.
As shown in Figure 4, dips--often called sags--are built at
points in the road grade, where water seeks the lowest spot
runs off the road. Dips must be constructed with exactness:
length and depth must be adequate to provide drainage, yet
excessive as to endanger traffic. Side drainage must be
so that the dips do not become ponds that hold water on the
roadway. Note that dips are not designed to handle
Water bars can be made of rocks, tree trunks, or compacted
(Soil is not normally used because it erodes too easily.)
two-thirds or three-fourths of the rock or tree trunk is
in the ground, leaving 2 to 4 inches exposed above the
The water bar should lie at a 20 to 45 degree angle from the
perpendicular of the road or trail. Water runs along the bar
its lowest point, where it runs off the side of the road.
shows how a water bar redirects the flow of water.
There are two common kinds of ditches:
trapezoidal ditches and
v-shaped ditches. The trapezoidal ditch is more difficult to
construct and maintain, but has a greater capacity than does
ditch of the same depth. The minimum size of trapezoidal
ditch that is practical to construct is 1-1/2 feet deep by 2
wide at the bottom. A special ditcher is required if a
ditch is to be built by machine.
Whatever the soil type, heavy rain is likely to cause
any ditch with a grade of over 4 percent. If the road is
to be used for a short time only, the deepening of the ditch
through erosion may not be a problem. But if the road is
to last, this erosion must be controlled, one way to do so
line the ditch with stone or other riprap material. Any
with a grade of more than 10 percent should be paved.
Check dams may be put into the ditch at intervals to change
single rush of water into a series of gentle flows. Their
and spacing are chosen to produce the desired slope, usually
of below 4 percent.
The spillway of a check dam must have a definite weir or
outlet. The bottom of the notch is the determining point
for calculating the grade. The bottom and sides of the dam
extend 6 inches into the ditch line. The spillway needs to
protected with rock riprap. The side of the dam that faces
also needs to be protected from scouring. The check dam
can be made of concrete, steel, rocks, logs, sandbags, or
(earth should be used only if it is well protected from
TYPES OF ROAD SECTIONS
Five typical road sections and their uses are profiled
Both steepness of the slope and the conditions of the
(e.g., whether the ground is dry or swampy) are factors that
determine which of the sections must be built at any given
during road construction to permit good cross-drainage. For
example, locations on the side of a hill permit good
They also have the advantage of involving a minimum of earth
moving since what is excavated can be used as fill. When
exceed 60 to 70 percent in grade, this advantage is lost
the roadbed must be placed in solid material, so all of the
excavated material becomes waste.
Turnpike Section. A turnpike section (Figure 6) is built on
relatively flat ground with less than 10 percent slope, for
example, in swampy areas. It is designed to raise the ground
above the water table to prevent the road from being
make a turnpike section, earth is extracted, or
a ditch and used to create a fill on top of the original
Fill Section. Fill Sections (Figure 7) are built on ground
slopes of up to about 50 to 60 percent. Where slopes are
than 60 percent, a fill section is used in drainage, raising
ground above the streambed to allow water to pass underneath
fill at ground level. To make a fill section, earth is taken
from another section of road (or from another area
and placed on top of the existing ground.
Through-cut Section. A through-cut section (Figure 8) is
often used when the road or trail goes through a ridge that
slope of less than 35 percent. This type of section involves
cutting earth from the ground. This earth then needs either
moved to another area where it will be used as fill or
Self-Balanced Section. A self-balanced section (Figure 9) is
built on slopes of between 10 and 60 percent. Building a
section requires that the amount of earth cut out of the
hillside be equal to the amount used to construct the fill
of the road.
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Full-bench Section. As shown in Figure 10, a full-bench
is built on slopes of 60 percent or greater. The term
refers to the flat bottom that is produced when the ground
away to create the surface of the road. The material that is
is either hauled off to an area needing fill, or it is
of over the roadside. Material that is disposed of over the
of the road is not stable and is not meant to support
MATERIALS AND SURFACING
Soil and rock are the basic materials for constructing roads
trails. Sometimes all that needs to be done to make these
usable is to remove the vegetation from their surface. It
is also necessary to remove soil that is high in organic
since it cannot adequately support the weight of traffic.
rockier the soil is, the firmer the road will usually be and
more support it will be able to provide. But rocky soil has
disadvantage of making the surface of the road rougher. This
often be resolved by spreading a layer of rocky soil to
support, and then covering the rocky layer with a 2- to
layer of sand-clay mixture to provide a smooth surface.
Usually, the soils are then shaped and compacted to provide
Generally speaking, the road that you are building must have
surface that can both shed water and carry the expected
you are constructing an all-weather road, you must find
materials that will bear up under the full range of weather
conditions. It is not always easy to find surfacing
that meet these needs. Information on what materials are
in your area can be obtained from your local highway
Crushed stone, stream gravel, and tuff are among the many
materials that can be used for surfacing a road. The
materials you choose should be tough and lasting. It is
to upgrade a poor base material such as clay by mixing it
rock or stream gravel, and adding a stabilizing agent like
chloride or sodium chloride. You then compact the mixture to
get a dense, dust-free surface. If the road is going to
large volume of heavy loads like lumber or coal, it may be
to pave it with asphalt to avoid long periods of shutdown
due to wet weather.
When the road is finished, short grass should be allowed to
around the ditches. A carriageway of 12 feet only should be
clear of grass. However, any culvert that crosses the road
be about twice as long as the road width so that there is
for two vehicles to pass each other at that point.
Maintenance is required to keep roads and trails properly
and fit for travel. Maintenance costs can be kept to a
in two ways: through
good initial construction, and through
proper, timely repair.
Periodic grading of the road surface is necessary to fill in
wheel ruts and to reshape the road. This is done with a
tractor-drawn grader, a bulldozer, a rubber-tired skidder,
a road drag. (A road drag is a platform weighted down with
and pulled behind a truck or tractor.
The purpose of grading is to restore the crown and to smooth
surface of the road. Be sure to maintain the slope of the crown
1/2 inch to 3/4 inch per foot, so that storm runoff can be
Shaping should be done at the end of the rainy season, after
heavy moisture is gone but before the road has become hard
dry. In the following months, routine smoothing should be
after a rain that has moistened the road but not made it
All ditches, culverts, water bars, and bridges must be kept
and in good repair. Particular attention should be given to
removing debris from culvert inlets, and to removing slides,
rocks, and other materials that have slipped off the banks.
When routine maintenance of ditches is being done, it is
not to undercut the backslope. This will cause sloughing
into the ditch, and bring about washout and bank erosion.
Excessively dusty roads cause hazardous driving conditions,
increase equipment maintenance costs, decrease the life of
and deteriorate road surfaces through losses in surface
material. Salts such as calcium chloride and sodium chloride
the least expensive and most effective materials for
dust. After shaping the road at the end of the rainy season,
while the ground is still moist, apply one pound per square
of road surface; during the dry season, apply one-half pound
Roads not used for long periods must be protected from
Drainage structures must be kept clean. Ditches and landings
should be planted with grasses and other vegetation.
GLOSSARY OF TERMS
Bar (water bar) - A barrier placed in the road to divert
off the surface and over the edge.
Borrow - Soil or rock material removed (borrowed) from one
to be used in another area.
Cross slope - The slope of the terrain.
Culvert - A conduit under a road or trail to allow the
Cut - The area excavated during construction of a road or
Dip - A low point in a road or trail grade.
Ditch - A low point in the excavated portion of the
intended for water flow.
Fill - The area where excavated material is placed during
Ford - A point in a stream or river where the water is
nonexistant during much of the year, and where the
soils will support traffic.
Grade - The slope of the road or trail along its
Slope - The unit of vertical distance per unit of horizontal
Waste - Excavated material that cannot be used in a stable
Armco Drainage and Metal Products. Handbook of Drainage and
Construction Products. Middletown, Ohio: Armco, [date].
Booth, E.D., and Woolverton, D.N. CARE Manual of Feeder Road
Construction. Freetown, Sierra Leone: CARE, 1977. This book
assumes an engineer is available.
Dalton, J.C. Maintenance of County and Rural Roads.
Experimental Bulletin 7. Moscow, Idaho: Idaho University,
de Veen, J.J. The Rural Access Roads Programme: Appropriate
Technology in Kenya. Geneva, Switzerland: International
Labour Office, 1980. Paperback.
Edmonds, G.A., and Howe, J.D.F.G. Roads and Resources:
Technology in Road construction in Developing Countries.
London: Intermediate Technology Development Group, 1980.
International Labour Office. Guide to Tools and Equipment
Labour-Based Road Construction. Geneva, Switzerland:
Labour Office, 1981. Paperback.
Jackson, Ian. Handbook of Fundamentals of Low-Cost Road
Awgu, Nigeria: Community Development Training Center, 1955.
Weigle, Weldon K. Designing Coal-Haul Roads for Good
Berea, Kentucky: U.S. Forest Service, Experimental Station,
This is an excellent reference for farm-to-market roads when
engineer is available.
SOURCES OF INFORMATION AND
Most countries have a department of transportation or
Within the department there are often sections that deal
rural transportation and are good first contacts. If there
such department, or if it does not seem willing to help, try
similar departments in other countries where the same
It may be difficult to find people who are interested in
you on small self-help projects. Do not increase the project
size just to obtain help. Remember what the users want.
American Association of State Highway
444 North Capitol Street, N.W.
Washington, D.C. 20001 USA
American Society of Civil Engineers
345 East 47th Street
New York, New York 10017 USA
Louis Berger International, Inc.
100 Halstead Street
East Orange, New Jersey 07019 USA
Brazilian Road Research Institute
Ipr/Dner Rod Pres. Dutra
KM 163 Cep 21240
Rio de Janiero, Brazil
1775 Massachusetts Avenue, N.W.
Washington, D.C. 20036 USA
Local Roads Program
218 Riley-Robb Hall
Ithaca, New York 14853 USA
Henry Grace & Partners
Garthcliff, South Ridge
St. George Hill
Weybridge, Surrey ENGLAND KT130NF
International Road Federation
525 School Street, S.W.
Washington, D.C. 20024 USA
National Association of County Engineers
326 Pike Road
Ottumwa, Iowa 52501 USA
National Feeder Road Fund
Federation Nacional de Cafeteros de Colombia
Avenida Jimeng 7-65
Bogota, Colombia 281 8964
National Institute for Transportation
and Road Research
P.O. Box 395
ND LEA/Ministry of Public Works
P.O. Box 152 KBYT
Jakarta, Selatan, INDONESIA
Royal Institute of Technology
Department of Highway Engineering
Brinellvagen 34, Stockholm S 100 44
Secondary Road Engineering
Federal Highway Administration
400 Seventh Street, S.W.
Washington, D.C. USA
U.S.D.A. - Forest Service
P.O. Box 2417
Washington, D.C. 20013 USA
Transportation Research Board
2101 Constitution Avenue, N.W.
Washington, D.C. 20418 USA
U.K. Transport and Road Research Laboratory
ENGLAND RGL 6AU
U.S. Forest Service
Berea, Kentucky USA
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