Podcast
Questions and Answers
What is the unevenness index a measure of?
What is the unevenness index a measure of?
- The cumulative measure of vertical undulations of the pavement surface recorded per unit horizontal length of the road. (correct)
- The cumulative measure of horizontal undulations of the pavement surface recorded per unit vertical length of the road.
- The average depth of potholes on the road surface.
- The total area of cracks present on the road surface.
Which unevenness index value indicates a road is considered to be in 'Good' condition?
Which unevenness index value indicates a road is considered to be in 'Good' condition?
- Less than 1500 mm/km (correct)
- Greater than 3200 mm/km
- Between 2500 and 3200 mm/km
- Less than 2500 mm/km
What is a disadvantage of white roads?
What is a disadvantage of white roads?
- Causes glare during the daytime (correct)
- Poor visibility at night
- Low durability
- High construction cost
Why should the pavement surface be impermeable?
Why should the pavement surface be impermeable?
What is considered the main enemy of pavement?
What is considered the main enemy of pavement?
What is the main purpose of providing camber on a road surface?
What is the main purpose of providing camber on a road surface?
In what unit is camber typically measured?
In what unit is camber typically measured?
Which type of road surface requires the highest camber in heavy rainfall conditions, according to IRC values?
Which type of road surface requires the highest camber in heavy rainfall conditions, according to IRC values?
What are the key objectives of providing camber on roads?
What are the key objectives of providing camber on roads?
Which mathematical formula represents a parabolic camber?
Which mathematical formula represents a parabolic camber?
What is the primary focus of highway geometric design?
What is the primary focus of highway geometric design?
Which of the following is a key factor influencing highway geometric design?
Which of the following is a key factor influencing highway geometric design?
What is a principal element of a highway cross section?
What is a principal element of a highway cross section?
Which of the following could be considered a marginal element in a highway cross section?
Which of the following could be considered a marginal element in a highway cross section?
In a typical multilane highway cross section, what separates opposing directions of traffic?
In a typical multilane highway cross section, what separates opposing directions of traffic?
Which of the following is included in the typical cross section of a two-lane highway?
Which of the following is included in the typical cross section of a two-lane highway?
What contributes to the life of the pavement and ride comfort?
What contributes to the life of the pavement and ride comfort?
For what traffic flows should roadway facilities be designed?
For what traffic flows should roadway facilities be designed?
What is the primary purpose of a shoulder on a pavement cross-section?
What is the primary purpose of a shoulder on a pavement cross-section?
What is the typical width range for shoulders on minor roads?
What is the typical width range for shoulders on minor roads?
What width range for shoulders may be considered for low-volume highways?
What width range for shoulders may be considered for low-volume highways?
Which of the following is NOT a function of road shoulders?
Which of the following is NOT a function of road shoulders?
What is the term used to define the borders of the right of way?
What is the term used to define the borders of the right of way?
Which of the following is typically found in a rural road cross-section?
Which of the following is typically found in a rural road cross-section?
What is a key difference between urban and rural road cross-sections, based on the provided information?
What is a key difference between urban and rural road cross-sections, based on the provided information?
Which characteristic of pavement is NOT mentioned as important for safe driving?
Which characteristic of pavement is NOT mentioned as important for safe driving?
What is a direct impact of friction between a vehicle's wheels and the pavement surface?
What is a direct impact of friction between a vehicle's wheels and the pavement surface?
Which of the following best describes 'skidding'?
Which of the following best describes 'skidding'?
What is the typical range of travel lane widths?
What is the typical range of travel lane widths?
What is the maximum permissible width of a vehicle?
What is the maximum permissible width of a vehicle?
Why is side clearance important for travel lanes?
Why is side clearance important for travel lanes?
What is the recommended lane width for multilane highways in Iraq?
What is the recommended lane width for multilane highways in Iraq?
What is the primary function of guard rails?
What is the primary function of guard rails?
According to the information provided, what happens when pavement surfaces are less than 6.75m wide regarding large trucks?
According to the information provided, what happens when pavement surfaces are less than 6.75m wide regarding large trucks?
What is the minimum lane width required for a single lane road, according to the content?
What is the minimum lane width required for a single lane road, according to the content?
At what embankment height are guard rails typically installed?
At what embankment height are guard rails typically installed?
What side clearance is needed on either side of a two-lane road?
What side clearance is needed on either side of a two-lane road?
What shapes are commonly used for guard rails?
What shapes are commonly used for guard rails?
When lane width is reduced from 3.65m, what happens to a highways capacity?
When lane width is reduced from 3.65m, what happens to a highways capacity?
In what type of area are sidewalks commonly provided?
In what type of area are sidewalks commonly provided?
What is the minimum clear width recommended for sidewalks in residential areas?
What is the minimum clear width recommended for sidewalks in residential areas?
What minimum lane width is required for each lane on a two-lane road?
What minimum lane width is required for each lane on a two-lane road?
According to AASHTO(American Association of State Highway and Transportation Officials) what aspect does table 1 represent?
According to AASHTO(American Association of State Highway and Transportation Officials) what aspect does table 1 represent?
What is the primary purpose of a median on a divided highway?
What is the primary purpose of a median on a divided highway?
What is the width of a median defined as?
What is the width of a median defined as?
Which of the following is a function of a median?
Which of the following is a function of a median?
What is the purpose of curbstone on urban highways?
What is the purpose of curbstone on urban highways?
Besides delineating pavement edges, what is another function of curbs?
Besides delineating pavement edges, what is another function of curbs?
What is the primary function of low or mountable kerbs?
What is the primary function of low or mountable kerbs?
In what type of area are semi-barrier kerbs most likely to be used?
In what type of area are semi-barrier kerbs most likely to be used?
Where are submerged kerbs typically used?
Where are submerged kerbs typically used?
What is the main purpose of gutters in highway design?
What is the main purpose of gutters in highway design?
What is a typical cross slope percentage for gutters?
What is a typical cross slope percentage for gutters?
What is the primary reason for providing side slopes on embankments and fills?
What is the primary reason for providing side slopes on embankments and fills?
What is the purpose of a recovery area on a road?
What is the purpose of a recovery area on a road?
For a cut height of 2 meters in rolling terrain, what side slope is typically recommended?
For a cut height of 2 meters in rolling terrain, what side slope is typically recommended?
What should be considered when slopes would be steeper than 1:2?
What should be considered when slopes would be steeper than 1:2?
What is the 'right of way' in the context of highway construction?
What is the 'right of way' in the context of highway construction?
Why is extra land purchased beyond the initial roadway during right-of-way acquisition?
Why is extra land purchased beyond the initial roadway during right-of-way acquisition?
What is the typical width of the right of way for a 2-lane road?
What is the typical width of the right of way for a 2-lane road?
Which roadside region connects the traffic lane/shoulder to the backslope?
Which roadside region connects the traffic lane/shoulder to the backslope?
Flashcards
Unevenness Index
Unevenness Index
Cumulative measure of vertical undulations of a pavement surface per unit horizontal length.
Effects of Unevenness
Effects of Unevenness
Affect operating cost, speed, riding comfort, safety, fuel consumption, and tire wear.
White Roads
White Roads
Roads appear bright at night but create glare during the day.
Black Roads
Black Roads
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Pavement Drainage Importance
Pavement Drainage Importance
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What is Camber?
What is Camber?
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Objectives of Camber
Objectives of Camber
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IRC Camber Values
IRC Camber Values
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Parabolic Camber
Parabolic Camber
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Straight Line Camber
Straight Line Camber
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Rural Road
Rural Road
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Urban Road
Urban Road
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Pavement Friction
Pavement Friction
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Skidding
Skidding
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Slipping
Slipping
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Highway Geometric Design
Highway Geometric Design
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Pavement Shoulder
Pavement Shoulder
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Design Speed
Design Speed
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Typical Shoulder Width
Typical Shoulder Width
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Volume and Capacity Factors
Volume and Capacity Factors
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Shoulder Width for Low-Volume Highways
Shoulder Width for Low-Volume Highways
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Environmental Factors
Environmental Factors
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Cross-Section Elements
Cross-Section Elements
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Functions of Shoulders
Functions of Shoulders
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Shoulder Use Cases
Shoulder Use Cases
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Marginal Elements
Marginal Elements
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Median
Median
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Side Slope
Side Slope
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Median Width
Median Width
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Functions of a Median
Functions of a Median
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Curb
Curb
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Functions of Curbs
Functions of Curbs
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Mountable Kerbs
Mountable Kerbs
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Semi-Barrier Kerbs
Semi-Barrier Kerbs
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Submerged Kerbs
Submerged Kerbs
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Gutters (Drainage)
Gutters (Drainage)
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Gutter Function
Gutter Function
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Traffic Lane
Traffic Lane
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Typical Travel Lane Widths
Typical Travel Lane Widths
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Pavement Width Impact
Pavement Width Impact
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Maximum Vehicle Width
Maximum Vehicle Width
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Side Clearance
Side Clearance
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Desirable Single-Lane Clearance
Desirable Single-Lane Clearance
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Minimum Single Lane Width
Minimum Single Lane Width
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Two-Lane Road Minimum
Two-Lane Road Minimum
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Lane Width (Iraq Highways)
Lane Width (Iraq Highways)
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Clear Distance
Clear Distance
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What are Guard Rails?
What are Guard Rails?
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Where are guard rails installed?
Where are guard rails installed?
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Common Guard Rail Shapes
Common Guard Rail Shapes
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Where are Sidewalks typically provided?
Where are Sidewalks typically provided?
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Where are Cycle Tracks provided?
Where are Cycle Tracks provided?
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Roadside Regions
Roadside Regions
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Right of Way
Right of Way
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Right of Way Width
Right of Way Width
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Side Slope Purpose
Side Slope Purpose
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Foreslope Definition
Foreslope Definition
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Retaining Walls
Retaining Walls
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Hinge Point
Hinge Point
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Study Notes
3.Side Slope
- Side slopes are constructed on embankments and fills to give stability for earthworks
- Serve as a safety feature by providing a recovery area for vehicles that run off the road.
- Three significant regions of roadside are hinge point, fore slope, and toe of the slope.
- The roadside slopes reduce the potential for loss of control of the vehicle
- Retaining walls should be considered where slopes would be steeper than 1:2, in filling or cutting is called side slope, which imparts stability to the earthwork.
Guide for earth slope design:
- Height of Cut or Fill (in m) and Earth Slope for Type of Terrain
- Flat or Rolling, Earth Slope is 6:1, 4:1, 4:1, 2:1, 2:1
- Moderately Steep, Earth Slope is 6:1, 4:1, 2:1, 2:1, 1.75:1
- Steep, Earth Slope is 4:1, 2.5:1, 2:1, 2:1, 1.75:1
- Height interval 0-1.2, 1.2-3, 3-4.5, 4.5-6, over 6 m
4.Right of Way
- It is the total land area acquired for the construction of a highway.
- Sufficient width should be purchased to accommodate all the elements of the highway cross section, any planned widening, and public utility facilities.
- Sometimes, rights of way are left vacant for future highway expansion.
- Right of way requirements for area are as follows:
- For 2 lane road = 150 ft (45 m) width of area.
- For 4 lane road = 250 ft (75 m) width of area.
- For 8 lane road = 300 ft (90 m) width of area.
- For Iraqi Expressway No One, a right of way width of 260 m has been provided, which included service roads.
2. Guard Rails
- Guard rails are Longitudinal barriers placed on the outside of sharp curves and at sections with high fills
- Primarily prevent vehicles from leaving the roadway.
- Installed at embankments higher than 2.4m and when shoulder slopes are greater than 4:1.
- Shapes commonly include the W beam and the box beam
Other elements
- Sidewalks are usually provided on roads in urban areas, but are uncommon in rural areas
- Generally, sidewalks should be provided when pedestrian traffic is high along main or high-speed urban areas.
- Sidewalks should have a minimum clear width of 1.25 m in residential areas and 2.5 m in commercial areas.
- Cycle tracks are provided in urban areas when the volume of cycle tracks is high, minimum width of 2 meter is required, which may be increased by 1 meter for every additional track.
1.6 :Medians
- The median separates lanes in opposing directions on a divided highway.
- Median width is the distance between the edges of the inside lanes of two adjacent roadways.
- Medians can be physical or painted separations, ranging from 1.2m to 24m or more sometimes.
- Functions of medians include:
- Providing a recovery area
- Separating opposing traffic
- Providing stopping areas during emergencies.
- Providing storage for left-turning and U-turning vehicles.
- Providing refuge for pedestrians
- Reducing the effect of headlight glare.
- Medians can be raised, flush, or depressed.
1.6 : Curbstone
- Curbs are raised structures, made of either Portland cement concrete or bituminous concrete, used on urban highways to delineate pavement edges and pedestrian walkways
- Curbs are also used to control drainage, improve aesthetics, and reduce right of way.
- Classified as either vertical or sloping indicating the boundary between the carriageway and the shoulder or islands or footpaths
Functions of curbs
- Drainage Control
- Roadway edge delineation
- Enhanced appearance
- Right of Way reduction
- Delineation of pedestrian walkways
- Reduction of maintenance operation
1.5: Shoulders
- Shoulders of a pavement cross section is contiguous with the traveled lane and provides an area for vehicles to stop when necessary.
- Shoulder surfaces ranges from 0.6m on minor roads to a maximum of 3.65m on major arterials
- Minimum shoulder width of 1.80-2.40m may be considered for low- volume highways.
- Asphalt and concrete surfaced shoulders should be sloped from2% to 6%; aggregate and untreated granular shoulders from 4% to 6%
- Graded and usable Sloped shoulders
- Functions of shoulders
- Accommodation of stopped vehicles (disabled vehicles, bus stops)
- Lateral support for the pavement
- Space for roadside facilities and bicycles, pedestrians and the vehicle
- Emergency Use
- Driving comfort (freedom from strain)
- Improvement In sight distance and capacity.
1.2: Pavement Surface Characteristics
- Pavement surface characteristics are important for safe and comfortable driving.
- Friction between the wheels and the pavement surface and drainage to water of the top of pavement influence horizontal curves the acceleration and deceleration ability of vehicles.
1.2.1: Friction
- Lack of adequate friction can cause skidding or slipping
Factors which affect friction coefficients
- Type Of Road Surface eg asphalt, concrete, or earth can determine roughness.
- Pavement condition with muddy, wet, or dry conditions can impact safe travel.
- Condition of tires through wear, new construction, or being old/dry can impact friction.
- Break efficiency
- Load on tires
- Tire pressure
- Temperture of tires and pavement
- Speed Of the vehicle
- Type Of the skid
Skid and slip
- Skidding is wheel skid without revolving
- Slipping is opposite skidding. In slip distance traveled by wheel less than normal
1.4: Width of Travel Lanes
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One lane width pavement dimensions depend on the width of the vehicle and the clearance.
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Traffic lane width improves operating speed and safety with adequate clearance.
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The traffic lanes are mostly in the range of 2.75m up to 3.75m.
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Two lane, two way rural road widths are 3m or 3.65m wide for both lanes.
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For lane widths less than 6.75m, the rate of crashing increases with the increasing size of trucks.
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Lane clearance is at 0.68m
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Minimum lane width for a single lane road is 3.75m
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Clearance required for a single lane road is 0.53 and 1.06m for each lane.
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In Iraq, standard lanes are generally 3.75m for multilane highways.
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Side travel Lanes require 3.6m of clearance as suggested by the AASHTO Green Book
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Number of travellanes in both directions is generally equal
Highway Geometric Design Control
- Geometric design is the determination of layout and features to ensure safety, comfort, and efficiency.
- Highway geometric designs are affected by these factors such as:
- Topography
- Design speed
- Traffic factors
- Volume and capacity factors
- Environmental factors
- Restrictions and others related
Elements of road design
- Cross-section elements are the travel lanes, shoulders, and medians.
- Marginal elements include roadside barriers, curbs, gutters, guard rails, sidewalks, and side slopes.
- Features of the cross-section influence payment life, riding comfort, and safety
1.3: Camber
- Camber is cross slope to raise middle of the road for water drainage
- Measurement is in n in N% EG, 1 in 50 or 2%
Objectives of camber
- Surface protection for gravel, and bituminous roads
- Sub-grade protection for proper drainage.
- Quick drying of pavement.
- IRC suggests various dimensions, depending on rain-cover requirements
- Concrete /Bituminous with 2% during heavy rain and 1.7% for light rain.
- Gravel/WBM with 3% during heavy rain and 2.5% during light rain.
- Earthen with 4% during heavy rain and 3% during light rain.
- Formula of camber is straight, parabolic and compound, including both shapes.
1.2.2: Unevenness
- Roads with high-quality pavers will develop unevenness later.
- Even a road can be developed with high-quality pavers and is possible to develop unevenness due to pavement failures. Affects vehicle operating costs, speed, riding comfort, safety, fuel consumption, and wear and tear of tires
- Pavement unevenness measures cumulative measure of vertical undulations.
Pavement Unevenness Chart (mm/km)
- An unevenness index value between 0-1500 is excellent
- 1500-2500 is satisfactory.
- 2500-3200 is bad/uncomfortable with speed over 55 kmph
1.2.3: Light of reflection
- White roads have good visibility at night with proper glares during the daytime.
- Black Roads has No glare anytime but poor visibility at night.
- Concrete roads has less visibility and less Glare.
1.2.4 Drainage
- Pavement surface cannot be impermeable and water cannot steep in
- Geometry and texture of pavement drains all water from its surface
- Drains are on both sides of pavement. Remember, pavement's main enemy is water.
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Description
This quiz covers key concepts in highway engineering, focusing on road design elements such as unevenness index, pavement properties, camber, and geometric design. It explores the purpose of various design features and factors influencing highway construction and maintenance.
