Highway Engineering

Friction course, which is known as porous asphalt, is often used as surface material in high speed roads and expressway. It is porous in nature which allows for speedy drainage of surface water. Road safety can be improved because it reduces the chance of hydroplaning/aquaplaning (i.e. there is a layer of water between the tires of the vehicle and the road surface. It may lead to the loss of traction and thus prevent the vehicle from responding to control inputs such as steering, braking or accelerating). It also decreases the splash and spray from vehicles in wet weather. It serves as a drainage channel for water to flow beneath the pavement surface.
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“Stone contact mechanism” applies to well graded aggregates coated with bitumen (e.g. dense bitumen macadam) where the traffic loads on bituminous roads are resisted by stone-to-stone contact and by interlocking and frictional forces between the aggregates. It is essential to adopt aggregates with a high crushing strength. The bitumen coatings on the surface of aggregates merely serve to cement the aggregates together.
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Roadbase is the most important structural layer in bituminous pavement. It is designed to take up the function of distributing the traffic loads so as not to exceed the bearing capacity of subgrade. In addition, it helps to provide sufficient resistance to fatigue under cyclic loads and to offer a higher stiffness for the pavement structure.
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Economic Evaluation of proposed Barwah-Dhamnod Toll Road by Dr.(Mrs.)Vandana Tare (Professor, Deptt. of Civil Engg. S.G.S.I.T.S., Indore (M.P) and Er. Raj Mohammad Khan (M.E. (Civil) Transportation Engg., Indore (M.P).

ABSTRACT
Road Traffic has been growing with very rapid rate, hence the traffic intensity and volume on the road is high. The present road network is necessary to improve to accommodate the future traffic and to provide the good riding quality. The development of Infrastructure has been done by the public sector through the fund collected from taxes, but huge fund are required for modernization of road network. Due to decreasing financial resources, government is not in position to invest the funds in those developments. This has brought to focus the need of attracting private investment in road in India.

The Barwah-Dhamnod road is proposed on B.O.T. system, starts from Barwah on Indore-Khandwa Road SH-27 and passing through Mandleshwar and joining NH-3 at Dhamnod. The total length of the road is 63 Kms and road passes through the districts of Khargon and Dhar. The details of road section Barwah-Dhamnod Road under study were collected through road inventory survey. The Traffic volume survey & Willingness to pay survey were also conducted on this road. The analysis of traffic volume data was done by projection up to 15 years. The need for widening of road from single lane to two lane is justified as per the capacity of road. Based on the data collection to achieve the toll fixation rates & to estimate the concession period, a methodology is adopted which includes generation of different module. Each module calculates the required results.
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A highway culvert is a drainage facility that allows water to flow under the road without causing any traffic disruption. Corrugated and spiral steel pipe are popular for culverts because they can be installed quickly, have long life, are low in cost, and require little maintenance. With corrugated steel pipe, the seam strength must be adequate to withstand the ring-compression thrust from the total load supported by the pipe. This thrust C, lb/ft (N/m), of structure is

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While taking a turn,the centifugal forces develop so a vehicle and its contents are immediately subjected to centrifugal forces. More is the speed of vehicle sharper is the curvature and thus the greater the influence on vehicles and drivers of the change from tangent to curve. When transition curves are not provided, drivers tend to create their own transition curves by moving laterally within their travel lane and sometimes the adjoining lane,which is risky not only for them but also for other road users.
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The figure below shows how the highway turning lanes can be classified:
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STRUCTURAL NUMBERS FOR FLEXIBLE PAVEMENTS

The design of a flexible pavement or surface treatment expected to carry more than 50,000 repetitions of equivalent single 18-kip axle load (SAI) requires identification of a structural number SN that is used as a measure of the ability of the pavement to withstand anticipated axle loads. In the AASHTO design method, the structural number is defined by

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The Geometric design of a highway consist of horizontal alignment, vertical alignment and cross-sectional elements.
Horizontal alignment of a highway defines its location and orientation in plan view. Vertical alignment of a highway deals with its shape in profile.

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Highway curves are designed so that safety and comfort of the driver is maintained. There is a gradual change from a tangent to the start of a circular curve.
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