Untarred and Dirt Road Development
Road development right from conception, planning and implementation is a major community problem in our societies. The unorganized process of development in our towns and cities especially in developing world is a major factor to put into consideration. The problem can be identified and be grouped into different subdivision as follows:
Inadequacy of road; some neighbourhood, towns and cities are not provided by enough relevant road development facilities;
Poor planning. In other instances, the roads are poorly planned. Bad road alignment, inadequate spaces at critical points, and more than necessary spaces in other less critical points
Poor Implementation. Some roads provided are not well constructed with appropriate ancillary infrastructures, while others are not well constructed. Some others are left as untarred and unpaved road without proper landscape and ground modeling treatment.
The aftermath of this are
reduced accessibility
and consequential reduced profitability.
Health Hazards.
Delay in man hour loss.
Road congestion.
Flood.
Loss of Aesthetics.
Inconvenience.
High cost of maintenance on the part of motorist.
In fact the list is endless. The article looks into the problem and narrow it down to our local access neighbourhood roads. This roads are by legislation under the jurisdiction of local governments in many developing countries like Nigeria. This article want to address this category of road in the light of the cost of implementing development of this road, considering the budget limit of the local government who are in charge of such roads. The intention is to look at the alternative implementation strategy in developing our access road.
The objectives therefore are to:
To evaluate present state of access road development in the country
Identify problems associated with such development strategy
Access alternative option of development using landscape and ground modeling techniques
Provide details of such alternatives
Access the advantages of the alternative suggested
Road System
Road can be broadly categorized into
Arterial Street and Highways. These are the one used primarily for heavy traffic,
Collector Streets are those that collects traffic from highways and feeds the minor roads.
Minor or access road are the ones used to access the abutting individual properties
Marginal access or service street are the one which are parallel to and adjacent to arterial and highways, they protect by separating traffic from the highways and access road
Alleys are minor road set aside to provide services such as emergency and conveniences for the properties. In Nigeria, any of this road can either be surfaced with bitumen of various thickness, interlocking paving stone, more recently 4.2 grade of Portland cement concrete and lastly earth road- the one without any form of hard surfacing
While there are many technical options available in road construction and development, the vehicle-accessibility and functionality of these roads is without respect to any form or level of development of such road.
The focus of this paper is on the earth road- i.e without any form of surfacing. It is no doubt the cheapest option of road development. Authorities may be hiding under the fact that road development is very expensive, which may in turn be the reason for abandoning our roads leaving them in a deplorable and sorry state.
In the light of the above, this article however brings the following fact into focus as follows:
An untarred and dirt road can be near as stable as their surfaced counterpart
An untarred and dirt road can be at least permit vehicle accessibility and meet the functional objective requirement of a road
A functional untarred and dirt road system can provide a way of improving accessibility in our towns and cities at an affordable cost, that can even be spearheaded by the community development organization (CDAs)
A well-constructed untarred and dirt road can serve as an effective intermediate phased implementation for standard road development. This is all because when the authorities decides later to pave f hard surfaced these road no major preliminary tasks shall be needed again.
New neighborhood development can become flexible in terms of cost of road development. This can promote private sector estate developers interest in housing provision.
Consequently provision of housing can be boosted.
It Starts from Subdivision Regulation and Practice.
( A Case Study of Nigeria)
In physical development planning, it is not only enough to estimate the need for land (Land Use). This is because space for activities is geospatially referenced and as such must be rationally positioned to achieve rational objectives. The practice through which details of the contents of built environment are laid out to enhance these objectives is called sub-division. It is spelt out in a document known as lay out plan and it is guided by the policy known as subdivision regulation. In Nigeria, the 1946 town and country Law midwifed by the British and adopted for Nigeria are properly supplemented by other provisions such as Land Development (roads) laws Cap 54 1933. Other provision is the Building Lines regulation, 1936.
All these laws under the colonial administration provides effective and coordinated framework for neighbourhood development in general and road development in particular. However, since the independence of 1960 and eventual development of political structure into federalism, the sense of coordination in land development has become fragmented among various states policy and various judicial interpretations.
In 1978, Land Use Decree was promulgated by the then military government specifying new policy on land tenure and ownership. Part of its provision discouraged the formerly well laid down policy of subdivision regulation. Thus laid foundation for haphazard neighbourhood development.
In 1992, at the National level a decree was promulgated by the then military government known as 1992 Urban and Regional Planning Decree. Few states, such as Lagos were quick to adopt the laws, while others until now have adopted it.
In 1978, Land Use Decree was promulgated by the then military government specifying new policy on land tenure and ownership. Part of its provision discouraged the formerly well laid down policy of subdivision regulation by the colonial masters as embodied into 1946 Town and country planning Act. This since then laid a foundation for uncoordinated land development in the country. Focus shifted to building development only by the three tiers of the government.
Hence effort should be made to restructure the administrative frame work for land subdivision regulation which should be focused as the starting point of development.
Technical Options: Ground Modelling (Shaping)
Ground Modelling is the art and science of shaping and arranging the surface level of land in such a manner to reduce friction between it and agents of denudation especially, run off water, thereby stabilizing the surface. It further involves coordinating the drainage system of a given site with overall natural hydrological cycle subsystem.
Then technological options such as Ground modeling i.e grading the road in such a way to achieve ideal gradient such as between 0.5% to 8% (1.8 degrees to 2.8 degrees) must be adhered to.
3. The ground modeling concepts of the road also should ensure that there is rational effort to direct run offs either towards drainage channels or on the surface of the road depending on the nature of the road in a coordinated manner. A road should be an integrated system of ground modeling directing the agents of denudation such as rain in such a way as to create minimum friction.
Road grading should avoid creating v-shaped, u-shaped and flat road surfacing without giving a sense of direction to the run offs of rain.
4. Side drainage channels should be constructed in such a way that they relate with the road level to receive run off water and channel it towards the natural drainage channel.
5. The construction of such channel should adopt a cheap option such as V-shaped channel. The channel does not need steel reinforcement because it is subject to side trust form shear pressure from the adjoining earth crust.
Picture 3. An earth road in an outskirt of town that is being graded haphazardly
Effort should be made to make provision for underground channel at every point where U-Shaped and V-shaped valleys cannot be avoided. Cheap precast round channel are commercially available for this purpose.
Empirical Case
The above picture depicts a road on a steep slope with a gradient threshold of 2.8 degrees. The side drainage constructed lies above the road level, thus creating a scenario of a U shape along cross section axis.
This contradict the principle of ground modelling as presented in this report. Hence the reason for instability of the surface of the road. Terrace Technique
A simple old technique of terracing if combined with the above surface modeling (shaping) can be employed to achieve great result.
The inclusion of concrete barrier is to form gentle slope that reduces the steepness of slope and reduce the velocity of run off and consequently the wearing off of top soil.
Model for ideal earth road development
Identify the drainage prospect in the neighborhood. Such may be gorge, stream, river, lake, public main sewer etc. This shall help a lot in drainage design.
Regard the altitude of this drainage prospect as the lowest point of your drainage design
The road being a linear open space should be viewed and handled along two dimensions of the longitudinal axis and the cross-sectional axis.
The gradient along the longitudinal axis should be between 1.8o and 2.8o.
The gradient of the slope along cross section axis should be towards the side drainage channel.
Where the gradient along longitudinal axis of the road is unavoidably greater than1.8o and 2.8o, then the gradient along the cross section should then be made greater than longitudinal axis slope gradient.
Also the option of terracing should be adopted on a very steep slopes.
Conclusion
With the above approach if properly implemented, it shall be amazing to discover that many of our minor road and the unpaved major road shall become sustainable and remain vehicle accessible throughout the year. This shall make it easier and affordable for relevant agencies or individual to maintain this road as well.
It is highly recommended that authorities and private organization involved in road provision should first target earth road construction as an intermediated phase in road construction. This shall enable then increase their capacity in road provision while expending less on capital outlay.
This same technique reviewed in this publication should be applied to bad portions of even damaged road.
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