Transport Based Project: Highway Engineering - Coursework Example

TRANSPORT BASED PROJECT- HIGHWAY eNGINEERING al Affiliation) Key words: Design Traffic, Ground Leveling, Geometric Design, Highway Structural Design. 1. INTRODUCTION Highway engineering provides the techniques and procedures required for planning, construction, and design of a highway installation, while setting them in their political and economic context. The discipline is involved in planning, designing, constructing, operating, and maintaining of bridges, tunnels, and roads to ensure effective and safe transportation of goods and people. Highway engineering takes into consideration the future traffic flows, highway interchange and intersect, geometric design and alignment, highway pavement design and material, structural design for the pavement thickness, and maintenance of the pavement. The geometric design for the highway must meet various service, safety and performance guidelines when the highways are designed for some site topography. Therefore, highway geometric designs are the highways visible elements. The design needs to take into account the social and environmental effects of the surrounding structure design. The design process need to consider the, design speed, number if lanes, cross-section, and alignment, grades, and super elevation, design traffic volume, sight distance, and the vertical and horizontal clearance. This is a report on transport related project aimed in producing the management and design solutions for the various highway-engineering activities. The paper utilizes and applies the techniques and principles in highway engineering modules. The paper will present in an appropriate structure report that incorporates the drawings and plans attached as the appendices. Additionally, the paper has the design tables, design data, design charts, and descriptions of the materials used in the project. The report further discusses the design and material alternatives, reasoning and justification, environmental and economic issues. Some of the relevant information is summarized in the drawing sheers as research evidence and the pertinent procedures. The highway operational performance is seen through the reaction of the driver to the design interaction and consideration (Wright & Paquette 2007). 2. DESIGN TRAFFIC 2.1 Assessment of Traffic The assessment of traffic expected to be using the junction and the roads is needed to evaluate the economy and possibly to appraise the junction options. The derivation will depend if the junction exists or it is new. In existing junction, turning movement, daily traffic flows and the peak hours can directly be measured. The measurement will have statistical errors, but may be applied to derive the design reference flows provided significant diversion from the present junction be not pushed forward at the present congestion level. Traffic flow data for the evaluation and design of the junction option will be; a manual classified turning point need to be carrier at junctions to find the turning proportions and the link flow volumes. In urban or inter-urban roads, the count need to incorporate the average peak in a normal weekday in a neutral month (Salter 2004). The timing is found to be difficult on recreational road. The objective is to observe the traffic flow that loads the junction heavily without causing congestion. Counts conducted on a weekday during peak season may be practical and appropriate. The design flows will be estimated by raising the hourly inflows rate for the evening and morning peak hours by parameters given in NRTF to provide range of high and low future year flows. The tidal flow patterns and turning proportions in the year may be helpful as foundation for the possible future development by rounding to enable the base year count to be accurate and the forecasting uncertainty. For instance, the observed proportion of the right hand of 18 per cent may be considered as 10 o 30 per cent in future. The flows may be estimated from a short-term period turning counts using various factors or domestic factor where they are available and suitable. The local factor’s accuracy need to be known. The growth factor should be used in estimating the range of traffic flows in future. When a junction is to offered on new roads or where there is flow of traffic through the existing junctions are expected to be altered significantly in future due to various traffic alterations or the congestion relief at the present junction, traffic flows of the future years for the design and junction evaluation need to be derived using a traffic model. The models have the ability to produce reasonable estimations of 12, 12 or even 24-hour ink flows in future. The estimates necessary for junction generation and evaluation can be provided but in the following ways (Salter 2004). The data can be derived from the estimation of traffic flows, by first calculating the AAHT flow, the data are then factored to represent the higher hourly figure using the specified factors. The output of the turning proportions is estimated so that the options of the junction can be designed. The output of the turning proportions needs to undergo manipulations so that the range of the turning movement can be covered. For instance the prediction’s traffic model for 152 cars turning left, 1708 cars going ahead , and 570cars turning right can be interpreted as a heavier straight under movement, with smaller proportion turning left and right. This will result to use the proportion of 1-10 per cent as turn left, 60-80 per cent as straight ahead, and 40-10 per cent as the right turn (Wright & Paquette 2007).. Traffic Data for Geometric Design It appears that there exists two feasible layouts; single lane dulling and ghost island each measured at 3.5 m wide. W = 6.00, Wcr = 0.00,Wcr = 3.50,Vrc - b = 250.0,Vr = 225.0, minor road,Vl = 225.0, for minor road; wb - c = 4.25,wc - a = 4.25, Single Lane Dualling;W = 8.00,Wcr = 10.00,Wc - b = 4.50,Vr - b = 250.0,Vr = 225.0, minor road;Vl = 225.0, minor road,wb - c = wb - a = 4.25, Traffic Data for Structural Design The structural design will based on lane that carried te highest number of MU and SU vehicle. The distribution factors in the table below outlined the MU, SU, and PV number that will be operating on the design lane. Rural Urban PV SU MU PV SU MU 2 or 3* 50% 50% 50% 50% 50% 50% 4 32% 45% 45% 32% 45% 45% ≥ 6 20% 40% 40% 8% 3 7% 37% GROUND CONDITION AND GROUND LEVELING Exploration of subsurface is an important section of the engineering survey for design and highway location. This includes the investigation of soil, soils identification, soil testing, and soil sampling relative to vertical and horizontal is highway alignment. Stability of the subgrade plays an important role in the performance and construction of pavement. The performance of pavements are directed to the physical and mechanical properties of the roadside and materials for the pavement structures. Stability of the subgrade is a function that affects the strength of the soil and its behavior in repeated traffic loadings. The properties influence the operation, construction, and performance of the highway structures. The road line subgrade need to be stable to prevent shoving and excessive ruttling during the construction process and to provide uniform rate from compaction and placement of the pavement layers. The mechanistic pavement design guidelines require that the support ratings for the subgrade be determined for the insitu soil of the project. The CBR values will be used in designing the pavement structure. The CBR are based in the data provided in the report for geotechnical project. The categories are in three forms; poor, granular, and fair. Based on the percentage of silt, sand,and clay found in the in situ soil, the values would be estimated as shown below There is a standard assumption that the frost penetration are appropriate and high water table Every CBR found in the soil report represents the mean soil condition within the specified project limit. Along the road line, the soil have fair to poor CBR values and need an improved subgrade layer. At such places, the marginally adequate soils are in existent, therefore, the geotechnical personnel will recommend lower than 12-inch thick upgraded layer. The improved subgrade is required to offer a stable and working platform. Therefore, any deviation from the standard thickness need to be supported by the engineer. The soil found on the road line will be improved to the standard depth with the help of the following alternatives: When selecting the best alternative, lime modification will be used to improve the subgrade layer. When the soil is found not to react with by-product lime, fly ash modification will be used to improved subgrade layer.Lab. testing might be needed to find the ability of fly ash to be used in modifying. In terms of embarkment settlement, underlying soils can settle whne it is under a newly constructed embankment leading to differential and ambarkment failures.The settlements are not cheap to fix and can lead to pavement dips. For every class of streets and roads. Construction need to be sequenced make sure that earthwork process is completed during a single construction period. After which paving will be initiated. If this fails with some level of certainty,special provisions need to be included that will make sure that the embarkment settlement is adequate. HIGHWAY GEOMETRIC DESIGN The first diagram is a plan metric view of the proposed and the existing horizontal alignment and bypass interaction improvement near the Blacksburg town. Diagram 1. The diagram below is a proposed and existing vertical profile of Tom Creek Road. HIGHWAY STRUCTURAL DESIGN ` The section describes the design for asphalt concrete pavement which conducts crucial traffic levels. It is normally more than 18-Kip 50000 ESAL over the period of performance. The asphalt concrete pavement the design will be based on understanding the flexible pavement structural number to withstand anticipated load traffic of the axle. The material used for the design of the pavement will be a minimum of two hundred mm of bound material normally specified to be RTA3051 and R73. Having presumptive subgrade CBR of 3 per cent. The mass concrete will be lean mix concrete defined to be R82. The strength and the thickness of the capping layer or working platform need to be taken into consideration to attain the effective subgrade strength. To design the pavement having a subgrade of less than 3 per cent at the construction time, the impact of the subgrade improvement or introduction of the working platform placed to enable construction to continue is normally ignored and CBR design of 3 per cent is adopted at the subgrade level. More improvements in terms of structure to a weaker subgrade may be modeled mechanically to attain effective strengths for over 3 per cent. The pavements having thin bituminous surfacing, seems to show that it may be applied in calculating the capping layers thickness and other layers of pavement above the main subgrade for a given design. For instance, from instance from figure it might be generated that 110 millimeter of materials having a 3per Cent CBR may be applied as capping layer over a natural subgrade having a CBR of 2 per cent producing a subgrade having 3 per cent as an effective CBR for DESA of 1 million as shown in figure 4. Figure 3 is developed to determine the composition of layers for a pavement having a thin bituminous surfacing. It is clear that for the pavement, CIRCLY can develop the same layer thickness depending on the limiting strain criteria for the natural subgrade. However, when the chart obtains the thickness of the capping layer for the subgrade improvement, the obtained thickness will not be appropriate for other configurations of pavement where the life of pavement may be under control by layers than natural subgrade. The issue of choosing the effective material property, modulus value, CBR, for the combined form of semi-infinite subgrade and a clapping layer. Here it is crucial to point out that for a given traffic loading there is likelihood to form a single pavement configuration that will carry out both two layer subgrade and subgrade of homogeneous semi-infinite. The similarity for the subgrades might not hold for other traffic holdings and pavement configurations. Figure 3 Figure 4 When constructing the pavements, it is crucial to point out the correct pavement and thickness of a base layer to handle the work. The most important design factors in constructing the pavement are the expected traffic and the underlying soil type. When the traffic value and the soil type is known, the graphs below specifies the pavement and thickness of the course layer for the asphalt pavement used in the project. The design procedures for the pavement are bases on the pavement life of 20 yrs. When developing the design formulas, the project collected and evaluated the test pavement constructed in various kinds of soil subgrades and tested to various traffic loads, and then formula was created based on the evidence of distress over period. The subgrade soil found below the pavement layer and the aggregate base course that was crushed, assisted in bearing the load of roadway traffic. The soil quality determined by the components determined the condition of the thick pavement. For instance, soils of high quality can accommodate more loads and need thinner layers of the pavement. The Asphalt design makes use of the Soil Stability Value as the concrete design make use of the K value. The values for K and SSV is identified through the designation of the AASHTO soil classification. The project used the good soil type. The values in terms of the SSV and K are shown in the table below. Soil Type Components Asphalt Design Concrete Design Good Gravel, sand; fine grained materials 4.8 225 Generally, the higher the traffic, the thicker the pavement. According AASHTO methodology, the light vehicles have a less impact on the life of a pavement, The fatigue failure is brought about by the heavier trucks. Though trucks are developed in different wheel loads and configuration, the procedures of the design are simplified with an equivalent single axle load representing 18,000 pounds that is exerted on one axle. Any truck causes a distress than the Equivalent single Axle Load. However, for the projects pavement design, the approximation of the design ESAL will be every truck pass is equivalent to one design ESAL. For the design, the number of trucks expected to pass in a single day is multiplied by 365 days every year and then it is multiplies by twenty years. For instance a street is anticipated to be carrying 100 trucks each day, the approximate design of 20 year Equivalent Single Axle Load will be 100*365 days*20yeaars which is equivalent to e730,000 design. It is noted that during the design of the actual pavement, the above approximation is normally replaced by various analysis, which entails the effects of various truck types on the asphalt, and factors of lane direction and distribution. The pavement thickened based on the traffic and soil for the selected soil type and the value of ESAL, is provided with the number as shown in the graph. In the project, good soil was used with an expectation of 100 ESAL design each day, the graph shows that the SN of 3.48 for the asphalt and a slab thickness to be7 inches for the cement concrete represented by a blue curve. The SN curve is shown to be very smooth, and is derived based on the formula specified in WisDOT’sFDM. The SN is taken to bethe targetnumber of the asphalt design. Since the SN target isknown, it is therefore possible to come up with various asphalt designs based on the formula ( Asphalt thickness * 0.44) + ( Base thickness * 0.14)= Target SN. The Asphalt layers are specified in increments of quarter inch and the base layer in increments of half, so the two varied ways of satisfying the example target of 3.48 will be 4.25 asphalt inches *0.44) + (12 inches *0.14)=3.55 theSN is slightly over the target. Consequently, (6 inches *0.44) + (6 inches *0.14)=3.48. This SN is right on target. The first of the designs has a course of about 3 times the asphalt layer. This is normaly considered as the standard design. The 2nd design employs a base layer of six inches. This is taken to be the minimum pavement platform for construction where the asphalt layer is maximised to attain the SN target. This design is called the Ling life, this is because it has a maximised asphalt layer with many advantages over the conventional design. The concrete slabs were specified in an increment of half inches, so the curves are stepped. With the help of a minimum construction benchmark, the course layer of the base is 6 inches. Since the asphalt base course is 6 inches, it is therefore,easy to put under comparison the concrete and the asphalt pavement design (long life). JUNCTION DESIGN Plan The four dimensional road junction will comprise of four roads; Road A, Road B, Road C, and Road D. Road A has a roadway consisting of the traffic lanes a1, a2, and a3 enter the junction, roadway Avm allows the movement passed the junction, and roadway Aisv having lanes d1,b3, and c2 for those that exit the junction. For road B, roadway Biv of the road having the traffic lanes b1, b2, and b3, for those entering the junction, Roadway Bvm to allow movement via the junction, and roads Bisv having lanes a1, c3, and d2, for those that exist the junction. Road C consists of the roadway Civ of the road consisting of the traffic lanes c1, c2, and c3 for those entering the junction, roadway Cvm to allow movement via the junction, and roadway Cisv having lanes b1, d3, and a2 to exit the junction. Road D has a roadway Civ having the traffic lanes of d1, d2, and d3 for entering the junction, roadway Dvm allows movement within the junction, roadway Disv has lanes c1, a3, and b2 to exit the junction. The overpasses of the junction include 1,2,3 ,and 4. Road A’s roadway having the traffic lanes a1 is developed in a tri-dimensional junction. In front of overpass 2, the roadway Avm comprises traffic lanes a1 and a2, is constructed in a tri-dimensional junction. Beyond the second overpass, roadway Avm comes in two, into the segment Ad and segment Ak. The right roadway having lane a2 join the traffic lane d3 and b1 for road D and road B, which are close on the right side, and led with curve to the right direction of road C thus becoming its roadway. Roadway Ak moves a left curve overpassing 3. After the overpass, roadways from road B and C joins from the two sides, with traffic lanes c1 and b2. Then via a curve on the right, the roadway continues to road D and builds its roadway Disv. Road B,C, and D’s roadway are constructed relative to road A. Junction and Traffic The four directional junction traffic is compared directly to the tri directional junction. Each right lane of the road is intended to drive to the right, the center lane is used in driving straight, while the left lane is intended for left driving. Based on the condition, it is possible to plan traffic lanes in various sequence. From the diagram above, traffic from any given road and direction has its separate lane, that meets other lanes via the tunnels or overpasses. Therefore, there is no need in changing lanes or giving ways on the junction. The design of the junction took into the consideration the idea that the vast cases of accident occur at junctions. In majority of nations, 60 per cent of accidents occur at intersections. Therefore, the design of the junction put into consideration the type, junction shape and the number of junctions occurring on the road axis and the effective and efficient design of every junction. The main aim of the junction is to increase comfort, safety, and convenience similarly enhancing the efficiency of movement for motor vehicles, pedestrians, buses, bicycles, and trucks. The junctions were intended to operate at places where the vehicles shared space with other road users. The negotiation for the junction required various simultaneously spaced decisions like selecting the right lane, maneuvering for the right position based on their need to decelerate, accelerate or even stop, and the need to choose safer gaps. The following areas were reviewed based on the decision to come up with a design that is satisfactory; the junction angle, vertical profile ordination, and vertical and horizontal alignment on the curves, improvement of the capacity, safety, operation through the process of channelization and the drainage need for the safety operation. The horizontally layout was carefully thought out, with more emphasis given to the horizontal and vertical alignment. When the two elements are poorly integrated, they will result to a junction that is uncomfortable and unsafe to use. The crucial safety aim is matching the speed which the drivers negotiate the junction the decision complexity. This was done by enabling simple merging maneuvering on high-speed traffic roads or by making sure that the drivers minimize speed when they approach the junction. The sight lines should offer drivers with the proper information so that right decisions can be made, but not tempting them to go for short gaps during traffic flows conflicts. More specifically the main assumption during the design of the junction include minimizing the location of traffic conflicts. Junction has various conflict points between the path of vehicles, and a proper design was aimed at reducing the severity of the perspective accidents at that point. The designed junction used a 32-conflict point at the roundabout as shown in the diagram below Additionally the sufficient sight distances was maintained. Proper sight distances when approaching the junctions and on the junction are a crucial importance for the safety of the junction. The junction was created in a vertical sag curve was considered to be the most favorable. Another crucial parameter is based on the prompt comprehension and concern of the junction’s layout and the driver’s operation especially the irregular junction users , therefore, selecting the travel speed and appropriate path where drivers are helped by the improved vertical and horizontal road marking and the proper junction layout. Based on the design of the transverse gradient and longitudinal section, it is crucial to design the road’s longitudinal section in both the access areas and the junction area so that the effective drainage and transverse gradient smooth transition can be achieved. Locating the curves may cause issues as visibility can be minimized, conflict point rise, and lane widening and super elevation makes the concern to be more complex. Additionally, the junction did not have the gradients of more than 3 per cent and not greater than 6 per cent in order to offer both the sight distances and improved comfort. Subsequently, the junction avoided being located at the vertical curves of the crest. The left turning movement was well determined and configured appropriately through the marked lanes and the traffic island. The designed took note of the high-risk movement associated with the left turns. Another concern was reducing the weaving areas. The junction choice depended on various factors whose importance varied between the cases. The most crucial ones include the traffic safety, road function and type, concurring legs, traffic type and volume, priority setting, and the operating and design speed. Other factors that were considered include the available room, adjacent land use, cost, network considerations, and environmental concerns. The choice of the junction type suited the type of road, the capacity, and the environment so that the readability of the junction and that of the road, as well as the level of safety can be satisfied. The figure below outline the guideline used in coming with the junction based on the traffic flows. The roundabout will have a higher capacity and they are designed to have a slightly higher advantage over the grade function. Other positive effect of the junction are based on the traffic island, pavement marking, delimiting traffic directions, and creation of the special lanes for the movements of the left turning. When the volume of traffic increase, the traffic signals will be increased. The junction is designed in such a way that it will reduce 30 per cent of the accidents on the road. There are various forms of the interchanges. The interchanges have separate lanes for every traffic stream with every movement which need crossing other traffic streams and the minimised to varying the traffic lanes. Various designs of the interchanges were built like the the diamond interchanges, cloverleaf interchange, or trumpet interchanges. The interchange used in this design was the diamond interchange. The interchange is comprehensive and sinple with ramps that are straight, with minor roads above the crucial road. This appeared to the safest interchange. The junction channelization was intended to segregate the traffic flows from one another and minimize the conflict area between various traffic streams intersection. It also provides the jucntion angles to provide goodvisibility. Additionally, it defines the patterns of driving and indicate the road type with junction priority. The process used the traffic islands whichh include the minor road channelization, left turn lanes, full channelization, and passing lanes.The junction used the channelised crossroad as shown below The selected channelization have a favourable effect on the rates of accidens at the crossroas. The junction also allowed the provision for redesigning. The redesidgning junction include changing angle between the road, changing the road gradient that approaches the junction, and other measures that improve the conditions at the junction. Designing is based on the change of the gradient, which is believed to reduce the high percentage of injuries. The junction re-allignement found to be great is shown below. LIGHTING DESIGN AND LAYOUT Read More