There is an increase in the development of the road sector. This sector is one of the most common and moreover, it is one of the cheapest as compared to other transportation means such as air. In essence, there is an emphasis on the development of this sector in order to cater for the increasing demand for road transport. Nevertheless, the surge in development of the road sector has been witnessed after the 20 the century, particularly because of the mobility of the road sector and the increase in the number of people that can be transported by a single automobile.
As of the recent past, roads have played a major role in connecting societies and communities. As such, it is a proven factor that the growth of a society will depend on the road connectivity. Proper planning followed by execution will lead to development of a particular road. A safe highway, nevertheless, is made up of pavements, pedestrian lanes, bike lanes, lighting, bridges and other road essentials.
The planning of the road design may be the most important aspect in the whole process. This is regardless of the type and nature of the road construction. The planning is usually followed by the design which is later on followed by the execution. This planning enables the engineer to take into consideration all aspects of the road. In this, the engineer can determine the risks likely to be encountered, and the estimation of the capacity of the road. Moreover, it enables the engineer to cater for any future changes that are likely to be experienced.
In essence, there is an increase in the design as well as the construction of roads. There are many factors that need to be taken into consideration during the design because there are major potholes that may lead to the project failure. As a matter of fact, not considering all the relevant factors may lead to a loss in lives as well as wastage of the taxpayers’ monies. Nevertheless, it is important to determine the necessity of the road prior to the construction. This is the role of the engineer. Furthermore, any adverse environmental factors likely to arise during the construction as well as in the life of the project should be determined.
As with the environmental aspects, the design stage must involve environmental specialists who determine any environmental factors that may arise along the proposed alignment of the road. Wildlife is an important factor because of the likelihood of the path to affect their ecosystems through pollution and cutting across major crossing channels. Moreover, it is important to consider the nature of the ecosystem and if the proposal is going to affect an endangered species, then a re-routing would be appropriate. However, the most economical method which may include the construction of other special structures may have to be considered.
An estimate of the expected amount of traffic also determines the design stage. This focuses on the current amounts of traffic as well as the forecasted amounts. However, the expected amount may be the major player in traffic estimation considering that the road is designed to cater for the future. As such, the design may shift from one location to the next Nevertheless.it is important to consider all the current highways and the demands that need to be catered for. Furthermore, this also determines the type of road structure to be constructed, either freeway, single lane or dual carriageway among others. This prevents redesign and reconstruction of the road structure.
However, it is important to consider the amount of funding available. Feasibility studies are meant to determine the costs to be involved in designing as well as construction of the road. Nevertheless, roads and other major structures are designed as a result of public private partnerships. If the funding is met, then the logistics that will be involved in the construction of the road have to be considered. The logistics of the road consider the road incline, the danger involved around bends and rivers among others. However, this is determined by the predominant means of transport along the route. Lorries and other trucks only manage certain logistics and if they are the predominant vehicles, then the design has to consider all these factors. In particular, the safety regulations and standards that may be used in the construction of the type of the road must be adhered to. The breaking and the speeding needs of the road will have to meet all the safety requirements. This also involves the design of junctions and intersections where the need be.
Attention to the minutest details have to be implemented during the road construction. This pertains to the quality of the materials used such as asphalt. Painting and road markings among others. As such, the designers have to follow the standards required for the construction of the new road.
Nevertheless, these stages of construction consider the orientation of the road structure as well as the specific goals that have to be achieved. Aligning the goas with the location requirements of the roads is a way of ensuring that the road is in line with the goals and development objectives of the country and the state.
As with the materials required, they are dependent on the type of the highway, the climate of the surrounding area, and the density that is expected among other factors. Some roads may require an asphalt paving while other regions may require a concrete pavement. However, is is important to use eco-friendly materials such as recycled plastic. Use of these materials ensure that the roads constructed are of superior quality and moreover, there is no significant damage to the environment. The materials used should be in line with the goals of sustainable development and are emphasized across the whole globe, let alone Australia. There are numerous books and articles that are used to guide the selection of the materials that may be used in each country and state throughout the globe.
However, there are many safety practices that need to be considered throughout the whole road design and construction process. In essence, the safety of the highway has been marked as an important point during the whole construction process. Nevertheless, highway safety is meant to cater for every road users including the vehicles, bikers and even pedestrians. As such, the zebra crossing and the traffic lights among other safety measures are imperative in the whole road design process. As sin the recent past, developments have seen the new age of GPS systems that have been used to effectively ensure that there is road safety.
The geometric design of Highways
The geometric design of a road section entails the analysis on the design aspects of the highway. As such, this involves the necessary calculation procedures that focus on ensuring that the road is safe and meets the necessary road construction standards. In essence, it is determined by the topography of the area in which the the road is to be constructed. This geometric design ensure that the service, the safety and the performance requirements are achieved by the design team. Geometric design of a road the therefore is based on several factors which include the traffic volume to determine the design life, the service, the width of the lanes, number of lanes, the design speed among others.
To begin with, the highest speed attainable and allowed at a particular section of the highway is known as the design speed,. Nevertheless, this is determined by the number of vehicles using the particular road section, the weather of the region, and the density of the traffic among others. These parameters determine the safety of the road section and as such, are very important. In essence, it is the design speed which is used by the engineer in order to design certain aspects such as super elevation, the alignment, the grade and other features of the rod. Other considerations such as the width of the road, the clearance and the ratio of the slopes is also determined by the road’s design speed.
On the other hand, the traffic volume used in the design refers to the average hourly traffic movement of the road. Determining this enables the engineering and design team to establish the total traffic that can use the road safely each day. The design traffic volume will be use alongside other road factors such as the service flow rate in order to ensure the safe construction of the road.
The sight distance is also an important aspect of road design. It refers to the clear distance that the road user can see without obstruction. Ensuring that there is an appropriate and sufficient sight distance prevents collisions and other accidents. However. It involves the analysis of all road users and in essence, it determines the stopping site distance, the passing sight distance and the decision sight distance among others.
The context of the roadway refers to the structural as well as the design aspects that the engineering team will need to consider in the road development. In essence, the roadway con text determines various factors such as the road cross section, the elements of the design and the street elements among other factors. Nevertheless, it pertains the minute details that have to be considered throughout the roadway design process. Therefore, the design team has to consider the road surrounding as well as its context for successful implementation of the whole construction process. One such important context may pertain the sensitivity of the location. A sensitive context will involve proper analysis and detailed investigation on the community and the environment. The contextual aspect of road design consideration therefore may make the whole design process much simpler and easier.
Safety is also imperative in the geometric design of a road cross section of roadway length.as a matter of fact, it is the primary consideration during the whole geometric design process. The road geometric design is meant to ensure the safety and stability throughout the whole road length.it is as such, meant to tackle all adversities that may affect the users of the road. However, the design and construction of the road has to be based on previous road crash records and audit services. Determining previous records of crash and other adverse effects of the road will enable the designer to ensure that such incidences are prevented. In essence, the design elements of the road section have to be picked from the analysis that involves their previous performance on the road and if there is need of additional measures.
Finally, the level of service is a fundamental fit in the geometric jigsaw. It is defined as a qualitative approach to establishment of the function of the road. In essence, the level of service determines various road characteristics such as the freedom to maneuver,, the comfort throughout the road, the safety of the road an d the travel time speeds among other factors.
The planning process.
As initially state, the road planning is one of the most important stages of road design and construction. The planning, in essence, establishes the other elements of the road with respect to present and future uses of the road. As a matter of fact, the whole purpose of the planning process is to ensure that all the road requirements are met with the least financial constraints. Finances limit the road design but the road should meet its intended purpose over the whole design life.
Nevertheless, the road planning process establishes the prescriptions and the object oriented goals of the whole project. The road development should be in synchrony with the locational needs. In essence, there is a coordinated working environment between the geologist land engineers, forest engineer, scientists the hydrologists and the biologists among other types of professionals. Analysis and consultations between these professional enables the road development process to have the least effects on the environment while meeting the needs of the community. Moreover, it enables the teams to establish solutions to every problem and as such, manage the finance. Nevertheless,the pattern that will be used by the road network will determine the total amount of area to be covered which will determine the finance and the route design elements.
It is important to identify the road pattern that ensure that there is the least density of roads in every unit area of the land but in the same sense, it should ensure that there is the least distance required for hauling. The density of the road determines the initial cost and maintaining it to a minimal ensures that there is an advantage in the initial cost estimation of the project. However, this also determines the future use of the road and the benefits that may be accrued. The acres of lands that are used in the road construction as well as the maintenance costs will depend on this initial land area that is used for the development of the road pattern.
Nevertheless, there are other parallel control criteria that may be in line with the sediment control of the road. These criteria should ensure that there is efficiency in the road network, there are economic advantages and the conservation measures are very efficient. For one, this may include the road location strategy that is in line with the afforestation requirements, the patterns used for harvesting, the propagation of the current ecosystems which may be those of fish or wildlife, the development of homes, and fire prevention strategies among others.
Moreover, the location and pattern should consider the future propagations that may be used for harvesting and timber restoration. Moreover, the plans for road construction should be accorded the right measures in order to ensure that there are proper preparations and planning of the whole design process. This may have to include the contractor who may be a road builder. Cost estimates, scheduling and the procedures will be dependent on these factors.
Another parallel criterion used in the road construction planning may involve the proper description and instructions regarding the initial design process. Proper instructions ensure that the chances of changing the original scope of work and the design are very minimal. Changes in the original design may result to a burgeoning cost of construction as well as other unforeseen and unwanted impacts such as destruction of the environment. Finally, it may be imperative to establish the cost of specific road elements as compared to the maintenance costs that may be required in the long run. Such an instance may include the establishment of the long term and short term effects of installing a bridge in the place of a culvert. All the costs to be incurred during the whole life of these two elements will determine the suitability of each. Therefore, there will be a comprehensive analysis and determination of the proper measures and details that will be implemented in each to ensure satisfactory road design and construction.
As a result, the planning stage will ensure that there is proper time frame that will be used to establish what economic as well as environmental justifications that will be used in the road design process.it is used to establish the methods that will be necessary in implementing the next stages of road costruction.However, sediment control has been known to increase the initial capacity of the outlay, it also increased the total cost that will be accrued from the4 road on annual basic. The annual costs will come from the reconstructions, repairs and the other maintenance costs. However, it is important to consider the opinion of environmental impacts of the outlay, mainly because of the likelihood that erosion may become a significant [problem in the long run of the project. Some considerations, in this case, may include the location of the control points and the repercussions both to the community and the environment because of the road design.
The design criteria of the roads.
The design criteria is a detailed list of all the necessary measures that should be taken to ensure efficiency of the road. The list, as such, is used to establish compliance as well as negotiation to the road design standards. The standards are used to establish and indicate the constraints of the environment, the objectives of the management, the safety requirements, the physical environment around which the road is to be designed, the requirements of the traffic, the level of service among other factors. Nevertheless, the objectives of each road are different and as such, they are expressed in relation to all the factors of the location.
There are other factors that need to be considered during the planning stage that entail the resources, the location, the constraints among other factors that are usually established during the preliminary and the planning stages of the project. To begin with, the objective to manage the resources determines the purpose of the road construction. This in turn establishes the economics that are to be accrued when the road becomes operational. As with the environmental and physical factors, the major purpose is to establish the design requirements of the area as per the soil, the topography, the climate, and the characteristic of the vegetation among other factors. However, it is also important to establish the constraints that can be attributed to the environment in order to establish proper remedies. However, this also includes factors that can be attributed to socio economics such as the state of the economy, the land ownership of the region, the land demarcations among others.
Another design criteria is the traffic needs of the region. The traffic requirements mainly pertain the average daily traffic. The ADT, nevertheless, should be established according to the groups of users that are predominant on that road. However, considering that there is a likelihood that there will be a change in the users, it is also important to understand what changes are likely to occur during the design life of the road. Understanding the changes that are likely to be experienced enables proper pavement design.
As with the level of service analysis, it mainly tries to establish the types of traffic likely to use the road and its network. Identifying the characteristics of the traffic that will use the road is important in trying to establish the road layout as well as the strength parameters. There are various tables that can be used in establishing the types of traffic that will be predominant and their characteristics. In turn, the planners are able to form a design criteria for the road and moreover, establish the conditions required for the efficient operation of the road. This is based on various levels of road construction that may be based on the travel time requirements, interruptions, maneuver and the operating costs among other factors. In essence, the final outcome of this process if the proper determination of the lanes, the spacing required for turn out, the sight distance, the design speed, the vertical as well as the horizontal curves and alignments, the clearance, the widening of the curves and the turnarounds among others.
Characteristics of the vehicles plays a significant part in the planning since it is a resource oriented objective of the whole construction process. Nevertheless, this criteria is used alongside the level of service and the traffic requirements in order to understand the types of vehicles that the road is designed for. Nevertheless, there are certain vehicular characteristics that usually determine the standards for the design that will be appropriate in the road construction. However, the engineer has to understand the type of vehicle that will be used in the design as well as the critical vehicle. By definition, the critical vehicle refers to the vehicle that is imperative for the operations of the road and is a frequent user of the road. On the other hand, the design vehicle refers to the vehicle that is an ordinary user of the specific road.
Another design criteria pertains the uses of the road. As such, it is important to understand the different road users and a categorical description be established. Users may include those who are involved in specific activities that surround the road such as timber transportation rock transportation among others. On the other hand, a category may be that of administrative users who may include wildlife specialist, biologists and ecologists among others. Following the description and categorical analysis of the road users is the estimation of the number that may be frequent. However, there should be an objective on the resource management of each category in order to establish horizon for the planning. However, the planning should be done over a number of horizons. Several horizons for the planning of the road uses may include transportation of rocks from one point to another, an access to a local community or ecosystem, an access and the transportation of timber material among others. However, this should be followed by the short term and long term uses of the road as per the categories identified. Identifying a change in the use of the road is imperative in designing the road as a channel to these road users.
Last, but not least, is the economics surrounding the design of the road. Road design is as a result of rigorous economic analyses with the criteria justifying the cost likely to be implemented. Nevertheless, the final outcome of this planning process should be an objectives documentation plan. This is a table analysis of all the factors taken in to consideration during the whole planning process in order to establish a proper design framework. In essence, this can only be done if there is an organized design criteria as well as determination of the management objectives.
The design elements of a road
All around the world, the majority of the road used are single lanes, most preferably with turnouts. However, considering that there is an increase in the need for single roads, the number is expected to rise because of the construction and reconstruction processes currently being witnessed. Moreover, these types of roads are very economic and environmental friendly. Nevertheless, it is the need to increase low volume and low speed roads that has contributed to this increase in the single lane roads construction emphasis
Data that may be available for use in the determining the design criteria to be used in the construction of roads include the accidents records, the expected rate of increase of the volume of traffic, the sizes of the expected vehicles and the time of the day when the road is highly used. One of the criteria used in increasing the size of the road is that a road that can be used by approximately 100 vehicles per day requires a two lane width road. Moreover, roads that have a vehicle volume of 250 vehicles per day will instantly require a two lane width road. Roads that have a vehicle daily traffic of about 100 may require the design of a single lane but there are also instances of roads being constructed using an intermediate criteria. The intermediate criteria of road construction is based on between 100 and 250 vehicles per day. This may require the analysis of other factors prior to the design and construction. Other factors may include socio political, the relationship between other road systems, the season, the criteria that will be used in managing the traffic and the available fund among other factors. Some of these data may be obtained from toads of similar stature in the area. Other elements may be based on information that is based on the probability of efficient service delivery. Nevertheless, it is the responsibility of all the stakeholders to ensure that the elements meet the requirements that are outlined indifferent road construction standards.
One of the elements that is imperative in efficient service delivery is the road width. Nevertheless, the main consideration of this element is the type and size of vehicles that are likely to be using the road. On the other hand, secondary considerations may be based on the design speed, the time of the day that the road is likely to be very active and the shoulder requirements among others. However, considering that various roads require the design of a ditch, the width of the road after this may limit the road usage and as such, it is up to the design team to ensure that there is proper clearance on both or one side of the road. Another criteria that may determine this width is mainly based on the design speed. Roads that are not properly tarmacked and are gravel min nature may require that the design speeds may be less than 60km/hr. A higher quality surface may sustain very high design speed, nonetheless.
As with the turnout, it determines the safety that will be accorded to other road users while maintaining the design speed of the road. Nevertheless, the rule of thumb is that the turnouts should be located on specific points that are mainly outside the section allowed for cuts. Other instances require that the turnout should be located on one of the side that vehicles are unloaded.
As with the turn-arounds, consideration should be made on the design as well as the critical speeds of the road. As a matter of fact, these turn-arounds should be located at the terminal points of roads which are single lanes. Other instances will require that these elements are points that may be used for closure. All these factors enable the design vehicle to turn-around without causing much incidents on a specific part of the road.
The widening of curves as well as the clearance height are other elements that are required for proper and efficient road design. As with the clearance, the commonly used horizontal clearance is about 1.2 m while the highly used vertical clearance is about 4.3m.tehse are clearnaces that are will commonly be used for roads that have a relatively lower design speed. Other roads that have higher design speeds may require a bigger clearance to maintain safety and convenience. On the other hand, widening of the curve is mainly implemented to ensure safety as well as convenience for roads that are used by bigger vehicles such as trailers and tractors. This [part of the curve that is widened, nevertheless, is usually considered as part of the way that will be used for travelling. The rule of thumb is that a curve widening approach is required when the curve is longer while a smaller widening will be required when the radius of the curve is smaller.
Speed and sight distances are designed to ensure that there is a lower likelihood of collision of accidents. Nevertheless, the design speed has been known to be the highest speed that can be maintained by the design vehicle over some specified portion of the road when all the factors are favorable and when the road features allow it. In essence, this deign speed will determined the sight distance, the stopping distance, the radius of curvature, the surface for running and the gradient of the road among others. Nevertheless, there should be proper evaluation in order to determine the best combination of both vertical and horizontal alignments that will lead to highest economic and environmental benefits. However, there are various tables and graphs that may be used to determine the vertical and horizontal alignment of the road with the safest sight distance.
The travel time is another important aspect to consider during the design phase of the project. Nevertheless, this time is highly influenced by the grade of the road, the nature, the alignment, the sight distance, the climate, the topography among other factors. However, the individuals’ performance and well-being is also a determinant in the travel time. Moreover, the influence of both horizontal and vertical curves on this time cannot be overemphasized because of the time requirements which are pivotal in determining the economics and the costs associated with the road section. Nevertheless, in determining the total travel time, the first step is to subdivide the road into various sections based on the horizontal and vertical alignment. The total travel time is calculated as a total of the total travel time of these different sections.
Last but not least, is the vertical and horizontal orientation of the road. Designing a road depends on the topography of the land as well as the presence of the obstacles on the right of way. A vertical curve primarily depends on the vertical alignment of the road profile while the horizontal curves depend on the vertical profile requirements of the road structure. However, these individual alignments usually depend on the design speed as well as the safety requirements of the country and state.
In essence, it has been stipulated that design speeds of about 15mph on roads of very low traffic volumes require the approximation of the circular curves. The main approximation depends on the geometric design of the road structure Nevertheless, the design has to consider the other determinants of the road structure such as the stopping distance and the curve widening.
The centerline for the road sections should have an approximate radius of 15m unless the road may be used for either recreational or other purposes such as administrative. However, the super elevation of the road should be designed based on the design speed. Road sections that have a design speed lower than 20mph should not have a super elevation mainly due to safety requirements. Other requirements are based on slow moving trucks as well as the road conditions. In this, the super elevation should not be more than 6% on roads that are likely to be subject to weather conditions such as snow and excessive rainfall areas. Furthermore, the sections that are for transition purposes should be provided in areas that are adjacent to the super elevated areas in order to avoid an abrupt change in the gradient requirements of the road alignment.
On the other hand, a vertical alignment should be provided on road sections that need a vertical detour. However, this is not recommended for grades that may exceed 10%.
The economic justification of a road project should be properly articulated prior to the initiation of the project. Road construction is a costly venture and as such, there needs to be proper justification. The justification may be achieved through increased connectivity, reduced travel time and reduction in the number of accidents among other factors. As such, it is important to conduct a feasibility and economic analysis amongst the different proposals in order to determine the most feasible option.
Nevertheless, the future development plan for the road is the main foundation of an economic analysis. This will involve the environmental evaluation as well as the economics of the road design. Moreover, the most economical planning method has to determine the number of roads that will sufficiently serve a particular location. The network has too have a very wide coverage so as to minimize the number of construction projects required. It is the function of the feasibility studies and the survey requirements. Nevertheless, the environmental consideration regards the delivery of sediments and the effects of improper drainage systems.
Nevertheless, the first stage in the economic analysis pertains the determination of the spacing of the roads as a requirements of the commercial usage. The most suitable method in this regard is the break-even analysis. The most economical method will be based on the optimum spacing.
The analysis will be based on the standards that need to be attained for a particular road project. The construction costs can therefore be based on the design data that is available for the materials and their cost estimates. Moreover, it is important to determine the maintenance costs that may be accrued per each section of the road and this is best determined from the local data.
In this section of the report, emphasis will be on the proposed road project. As with many other road design projects, the following will be provided in detail; the pavement design, intersection design, storm water design and the environmental considerations. Some of the parts in this section will involve the use of road software However, it will be based on the information available from the local as well as the government agencies in Western Australia
The pavement design
By definition, the pavement refers to the actual surface on which the vehicle travels. It is the whole structure that underlies the natural subgrade and is composed of various layers made up of different materials. The purpose of the pavement is to provide friction that enables the vehicles to move safely from one region to another. However, it play the role of transferring the wheel loads to the underlying soils. Based on this, the pavement may be the most important element of the road construction and as such, about half or a third of the total cost of road construction is allocated to pavement design.
Nevertheless, the choice of the pavement will be based on the type of underlying soils as well as the materials available for construction. Nevertheless, it is important to understand the initial cost of the pavement, the maintenance costs, the environment, the intensity of the traffic and the wastes from industries. This comes in to play when choosing the type of pavement. However, the construction and design phases, regardless of the type of pavement, are two: the foundation design and the thickness design. The former refers to the design of the lower layers which ae the subbases and the subgrade. On the other hand, the thickness design pertains the design of the upper layers of the road with particular emphasis on the surfacing.
However, there are fundamental cannons that guide the design and construction of a pavement. To begin with, the pavement should be of sufficient thickness so that the wheel load can be distributed substantially to the soil. This prevents cracking and fatigue. Secondly, the pavement should be of sufficient structural strength so that it can manage all the loads that may be imposed. Thirdly, there should be a sufficient coefficient of friction in order to reduce the chances of skidding. However, the surfacing should be smooth enough to ensure that the road users are comfortable. Moreover, it should be impervious in order to reduce the chances that water will seep into the subgrade. The other factor regards the dustproof nature. These pavements should be dustproof so that there is a reduction in air pollution and visibility is not impaired. Finally, the road should produce very minimal noise throughout its design life. The design life is usually long and there should be minimal maintenance costs.
The types of pavements
Road classification is usually done based on the structural characteristics. In this there is the flexible and rigid pavements. Nevertheless, the former transfers the wheel load through the grain contact over the whole granular structure. These roads usually have very less flexural strength. As with the latter, load transfer s through the flexural properties. The load from the wheel is transferred through the flexural capabilities of the materials used, such as concrete. However, there are road pavements that combine the properties of the two. These are known as composite pavements and transfer loads through grain to grain contact as well as flexural strength. However, the construction costs are very high in these types of pavements and as such, construction is rare.
The flexible pavement
Load transfer is through the contact of the grains. Nevertheless, the wheel load is usually distributed over the pavement surface and it reduces as it goes downwards. It is from this response that flexible pavements have a number of layers. An increase in the number of layers means that the stresses will be at a minimal when reaching the subgrade. However, the layer that is directly under the wheel load has to be of the highest quality in order to sustain the very high compression strengths.
As the stresses are distributed downwards, there is a reduction in the Intensity. This means that materials of lower quality can be used.