Test: Transportation Engineering

Nagpur road plan or First 20 year road plan (1943 - 63):

In this plan road network in the country was classified in to:

i) National Highways

ii) State highways

iii) Major District roads

iv) Other District roads

v) Village roads

In the Nagpur conference, recommendations were made for the geometric standards of roads, bridge specifications and highway organisations and two plan formulae were finalised. This two plan formulae assumed star and Grid pattern of road network.

Note:

1. The rectangular or the block pattern has been adopted in the city roads of chandigarh.

2. Radial and circular pattern of road network is adopted in Connaught place (New Delhi).

Camber is the slope provided to the road surface in transverse direction to drain off rain water from the road surface.

1. For WBM roads in localities of heavy rainfall, the recommended value of camber is 1 in 33.

2. For WBM roads in localities of light rainfall, the recommended value of camber is 1 in 40.

The coefficient of friction reduces considerably when the pavement surface is smooth or wet. The coefficient of friction also decreases slightly with the increase in temperature, tyre pressure and load. Smooth and worn out tyres offers higher friction factors on dry pavement then new tyres with treads because of larger area of contact. But on wet pavements new tyres with good treads give higher friction factors than worn out tyres. This is because the lubricating effect of water on the wet pavement is reduced as the water entrapped between the tyre and pavement escapes into the treads of the tyre.

In Dorry abrasion test, the coefficient of hardness is calculated as follows:

Coefficient of hardness 

Coefficient of hardness 

The Border roads organisation has classified the hill roads as follows:

1) National highways: These are the roads of national importance and are designed and constructed as per I.R.C specifications.

2) Class-9 roads: These roads are 6 meters wide and are designed to carry 3-tonne vehicles.

3) Class-5 roads: These roads are 4.9 meters wide and are designed to carry 1-tonne vehicles.

4) Class-3 roads: These roads have width ranging between 2.45m to 3.65m meters and are designed to carry jeeps.

How to remember?

As it is clearly observed that as class of roads increased, the corresponding width and carrying capacity also increased.

A pavement which consist of a mixture of asphaltic or bituminous material and aggregate placed on a good quality and compacted granular material is termed as flexible pavement. The flexible pavement has low or negligible flexural strength. Example-Water bound macadam roads.

Water bound macadam roads: The roads whose wearing course consist of clean crushed aggregates, mechanically interlocked by rolling and bound together with filler material and water and laid on a well compacted base course, is called water bound macadam road.

Higher the value of group index, poorer is the soil as subgrade material.

Basic capacity: The basic capacity is the maximum numbers of passenger cars that can pass a given point on a lane or a roadway during one hour under the most ideal roadway and traffic conditions that can possibly be attained.

Possible capacity: It is the maximum number of vehicles that can pass a given point on a lane or roadway during one hour under the prevailing roadway and traffic conditions.

Practical Capacity: It is the maximum number of vehicles that can pass a given point on a lane or roadway during one hour with creating unreasonable delay under the prevailing roadway and traffic conditions.

Design capacity: it is the practical capacity or a smaller value determined for use in designing the highway to accommodate the design hourly volume.

Theoretical Capacity: It is the number of vehicles passing any point in one hour per lane.

Where,

l = length of wheel base = 6.3 m

R= mean radius of curve path = 40 m

A horizontal curve provides change in the direction of the center line of a road while a vertical curve on a road provides change in gradient. The circular and transition curves are used as horizontal curves and the parabolic curves are used as vertical curves.

Hot mix asphalt is heated and poured at a temperature ranging from 300 to 350° Fahrenheit i.e. {148. 89°C to 176. 67°C}.

Bitumen adheres well to all normal types of road aggregates provided they are dry and free from dust. In the absence of water, there is practically no adhesion problem of bituminous construction. Adhesion problem occurs when the aggregate is wet and cold. This problem can be dealt with by removing moisture from the aggregate by drying and increasing the mixing temperature. Further, the presence of water causes stripping of binder from the coated aggregates. These problems occur when the bitumen mixture is permeable to water. IRC has specified the maximum value of stripping value of bitumen not to exceed 2%.

Seal Coat: Seal coat is a thin surface treatment used to water-proof the surface and to provide skid resistance.

Tack Coat: Tack coat is a very light application of asphalt, usually asphalt emulsion diluted with water. It provides proper bonding between two layers of binder course. It must be thin, it uniformly covers the entire surface and it sets very fast.

• Bituminous materials consist of bitumen which is a black or dark coloured solid or viscous cementitious substances consists chiefly high molecular weight hydrocarbons derived from the distillation of petroleum or natural asphalt. It has adhesive properties and is soluble in carbon disulphide.
• Tars are residues from the destructive distillation of organic substances such as coal, wood, or petroleum and are temperature sensitive than bitumen.
• Bitumen is soluble in petroleum oils where unlike tar.

Basic capacity,

Capacity, 

Where S = Spacing between two vehicles

V = Maximum velocity

Correct Answer :- c

Explanation : Passenger Car Equivalent (PCE) or Passenger Car Unit (PCU) is a metric used in Transportation Engineering, to assess traffic-flow rate on a highway.[1]

A Passenger Car Equivalent is from Assam. essentially the impact that a mode of transport has on traffic variables (such as headway, speed, density) compared to a single car. For example, typical values of PCE (or PCU) are:

private car (including taxis or pick-up) 1

motorcycle 0.75

bicycle 0.5

horse-drawn vehicle 4

bus, tractor, truck 3

The tie bars in a concrete pavement are provided in “Longitudinal Joint”.

Tie bars are not load transfer devices but serve as a means to tie two slabs. Hence tie bars must be deformed or hooked and must be finally anchored into the concrete to function properly. They are smaller than dowel bars and placed at large intervals. They are provided across longitudinal joints.