Podcast
Questions and Answers
Which of the following is NOT a basic feature of a highway?
Which of the following is NOT a basic feature of a highway?
Highway geometric design primarily aims to optimize which of the following?
Highway geometric design primarily aims to optimize which of the following?
Which factor is NOT considered in the geometric design of highways?
Which factor is NOT considered in the geometric design of highways?
What is the primary purpose of cross-section elements such as camber and superelevation in highway design?
What is the primary purpose of cross-section elements such as camber and superelevation in highway design?
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Which of the following influences highway geometric standards the most?
Which of the following influences highway geometric standards the most?
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Which of the following is not considered a principal element of a highway cross-section?
Which of the following is not considered a principal element of a highway cross-section?
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What impact do the features of the cross-section of the pavement have?
What impact do the features of the cross-section of the pavement have?
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What is a key factor for designing horizontal curves on roads?
What is a key factor for designing horizontal curves on roads?
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Which condition is not a factor affecting friction coefficients?
Which condition is not a factor affecting friction coefficients?
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What does the unevenness index measure?
What does the unevenness index measure?
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What is the maximum acceptable unevenness index value for a road to be considered good?
What is the maximum acceptable unevenness index value for a road to be considered good?
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Which of the following is NOT considered a characteristic of the pavement surface that contributes to safe driving?
Which of the following is NOT considered a characteristic of the pavement surface that contributes to safe driving?
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What defines skidding in the context of vehicle movement?
What defines skidding in the context of vehicle movement?
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What is the main benefit of using black roads during the daytime?
What is the main benefit of using black roads during the daytime?
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What is the purpose of camber in road design?
What is the purpose of camber in road design?
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What is the desirable side clearance for single lane traffic?
What is the desirable side clearance for single lane traffic?
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If the width of a traffic lane is reduced from 3.65m, what is a likely consequence?
If the width of a traffic lane is reduced from 3.65m, what is a likely consequence?
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What should the pavement surface be to prevent seepage of water?
What should the pavement surface be to prevent seepage of water?
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What is one of the primary enemies for pavement according to road design principles?
What is one of the primary enemies for pavement according to road design principles?
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Which road surface typically has better visibility at night?
Which road surface typically has better visibility at night?
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What is a negative consequence of having too steep a camber slope?
What is a negative consequence of having too steep a camber slope?
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What is the minimum clear width for sidewalks in commercial areas?
What is the minimum clear width for sidewalks in commercial areas?
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When is a right of way typically purchased?
When is a right of way typically purchased?
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What is the required minimum width for cycle tracks in urban areas?
What is the required minimum width for cycle tracks in urban areas?
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Which roadside region is NOT important for reducing the potential for vehicle loss of control?
Which roadside region is NOT important for reducing the potential for vehicle loss of control?
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What is the recommended right of way width for a 4 lane road?
What is the recommended right of way width for a 4 lane road?
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What feature does a side slope provide for an embankment?
What feature does a side slope provide for an embankment?
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When should retaining walls be considered in road construction?
When should retaining walls be considered in road construction?
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Which factor does NOT directly govern the width of the right of way?
Which factor does NOT directly govern the width of the right of way?
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What is the minimum recommended lane width for a two-lane road?
What is the minimum recommended lane width for a two-lane road?
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What is the primary purpose of curbs on urban highways?
What is the primary purpose of curbs on urban highways?
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Which of the following is NOT a function of road shoulders?
Which of the following is NOT a function of road shoulders?
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Which type of kerb is specifically designed to discourage vehicles from leaving the pavement?
Which type of kerb is specifically designed to discourage vehicles from leaving the pavement?
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What is the typical range of widths for medians on divided highways?
What is the typical range of widths for medians on divided highways?
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What is the minimum shoulder width recommended for low-volume highways?
What is the minimum shoulder width recommended for low-volume highways?
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What is the typical cross slope percentage for gutters located on the pavement side of a curb?
What is the typical cross slope percentage for gutters located on the pavement side of a curb?
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In what scenario are guard rails typically installed?
In what scenario are guard rails typically installed?
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Which of the following sloping percentages is recommended for asphalt surfaced shoulders?
Which of the following sloping percentages is recommended for asphalt surfaced shoulders?
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Which type of kerb encourages traffic to remain in through lanes while allowing easy access to the shoulder?
Which type of kerb encourages traffic to remain in through lanes while allowing easy access to the shoulder?
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Which of the following is a typical function of a median?
Which of the following is a typical function of a median?
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What is a common characteristic of sidewalks in urban areas compared to rural areas?
What is a common characteristic of sidewalks in urban areas compared to rural areas?
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What is the general maximum width for major arterial pavement shoulders?
What is the general maximum width for major arterial pavement shoulders?
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In terms of shoulder surface slope, what is the recommended range for untreated granular shoulders?
In terms of shoulder surface slope, what is the recommended range for untreated granular shoulders?
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What is the main function of guard rails on highways?
What is the main function of guard rails on highways?
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Which of the following types of kerbs is designed for rural roads and provides lateral confinement for pavements?
Which of the following types of kerbs is designed for rural roads and provides lateral confinement for pavements?
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Study Notes
Highway Cross-Sectional Elements
- A typical highway section includes pavement (asphalt or concrete), subbase (sand, gravel, or stone), paved shoulders (3.0m), travel lanes (3.7m or more), a median (variable width), and a pipe foundation underdrain.
- Dimensions of paved shoulders are 10 ft (3.0m) and travel lanes 12 ft (3.7m).
- The median's width varies.
Highway Geometric Design
- Geometric design involves designing visible highway components, making the designer the architect of the roadway.
- Basic highway features include the carriageway, median strip, shoulders, horizontal & vertical alignments, intersections, and acceleration/deceleration lanes.
- Highway geometrics are visible road elements providing optimal traffic efficiency and safety.
- Geometric classifications include cross-section elements (camber, superelevation), horizontal/vertical alignments, and sight distances (stopping, overtaking).
Highway Design Control
- Highway design considers driver comfort, vehicle safety, and efficiency, along with project-specific factors.
- Key factors include topography (plain, rolling, mountainous), design speed, traffic factors (vehicle characteristics), volume/capacity factors, environmental factors (landscaping, noise, air pollution), and service level.
1-Cross-section Elements
- Fundamental highway cross-section elements consist of travel lanes, shoulders, and medians (in multilane highways).
- Secondary elements include roadside barriers, curbs, gutters, guardrails, sidewalks, and side slopes.
- Road surface features affect pavement lifespan and driver comfort/safety.
- Diagrammed cross-sections are provided for multilane and two-lane highways demonstrating design details, including slopes, medians, and shoulders based on design considerations.
Pavement Surface Characteristics
- Crucial aspects for safe/comfortable driving include friction between wheels and pavement, surface smoothness, light reflection characteristics, and water drainage.
- Factors influencing friction coefficients include road surface type (asphalt, concrete, earth), pavement condition (rough, smooth, oily, muddy), tire condition (new, old, type), tire load, tire pressure, temperature, vehicle speed, and skid type.
- Skidding is wheel skidding without revolving, while slipping is the opposite.
Unevenness
- Pavement unevenness, even in high-quality roads, can result from failures affecting vehicle operation costs, speed, safety, and tire wear.
- Unevenness is measured by the Unevenness Index, the cumulative measure of vertical undulations per unit horizontal road length.
- Unevenness index values less than 1500 mm/km are considered good, between 1500 and 2500 mm/km satisfactory, and greater than 3200 mm/km uncomfortable, even at 55 kmph.
Light of Reflection
- White roads offer good nighttime visibility but can cause glare.
- Black roads have less visibility at night but are not glaring during daytime.
- Concrete roads offer good visibility and reduced glare.
Drainage
- Pavement surfaces need to be impermeable to prevent water seepage.
- Pavement design should facilitate rapid water drainage.
- Drainage systems—often gutters—should be well-designed on highway sides.
Camber
- Camber is a transverse slope in the road surface to drain rainwater.
- Too steep a camber can promote erosion.
- Standard camber measurements are specified as per road type (1 in 50 or 2%).
- Camber objectives are surface protection (for gravel/bituminous roads), subgrade protection, and pavement quick drying for increased safety.
- Types of camber (parabolic and straight line camber) and IRC values (based on the amount of rain) are presented for different road surface types.
Width of Travel Lanes
- Pavement width depends on traffic lane width and number of lanes, and vehicle/side clearances.
- Typical travel lane widths range between 2.75m and 3.75m.
- Factors influencing lane width selection include pavement surface width (<6.75m), crash rates for large trucks, and highway capacity.
- Minimum lane widths (3.75m/single lane) and vehicle width (2.44m) are presented for roadways.
Shoulders
- Shoulders are contiguous with travel lanes, providing areas for vehicle stops and supporting the pavement.
- Shoulder widths range from 0.6m to 3.65m.
- Slope values for asphalt/concrete and granular/untreated shoulders may vary (2-6% and 4-6%, respectively).
- Graded & usable shoulder features, like usable shoulder, rounded shoulder, etc.
Medians
- Medians divide opposing traffic lanes on divided highways.
- Median widths range from 1.2m to 24m or more.
- Functions include recovery areas for out-of-control vehicles, traffic separation, emergency stopping, turning spaces, pedestrian refuge, and glare reduction.
- Medians can be raised, flush, or depressed.
Curbstone
- Curbstones are raised structures made of Portland cement concrete or bituminous concrete, delineating pavement edges and providing walkways. They improve aesthetics and aid drainage control.
- Curb classifications are noted, including vertical and sloping kerbs, which mark the boundary between the carriageway, shoulder, or islands/footpath.
- Curb functions include drainage control, roadway edge demarcation, improved appearance, restricted right-of-way (reduction), and pedestrian walkway delineation, reduction of maintenance operations.
Gutters
- Gutters (drainage ditches) are positioned on the pavement's curb side to provide primary drainage.
- Gutters are sloped to prevent traffic hazards.
- Gutter widths generally range from 0.3m to 1.8m, with slopes ranging between 5 and 8%.
Guard Rails
- Guard rails serve as longitudinal barriers on sharp curves and high embankments to prevent vehicles from leaving the roadway.
- They are commonly installed at embankments ≥ 2.4m and when shoulder slopes exceed 4:1.
- Common guard rail shapes include W-beamed and box beams.
Sidewalks
- Sidewalks are predominantly located in urban areas and are uncommon in rural settings.
- They are installed where pedestrian traffic is substantial along major roadways, with typical widths ranging from 1.25m to 2.5m for urban areas and residential areas, respectively.
Side Slopes
- Side slopes on embankments and fills provide stability and recovery areas for vehicles that have lost control.
- Side slopes create graded regions (fore slope, hinge point, toe of slope) to prevent vehicle loss of control.
- Stability is affected by slopes and soil types; retaining walls may be needed when slopes exceed 1:2.
Right of Way (ROW)
- Right of way comprises the total land area designated for highway construction.
- Sufficient width is needed for highway cross-sectional elements, planned widenings, and public utility facilities.
- Right of way areas may exceed roadway needs to accommodate future expansion.
- Specific right-of-way width considerations (in feet/meters) are presented for various roadway construction types (2-lane, 4-lane and 8-lane).
- Factors determining ROW width include formation width, embankments/cuts' heights, side slopes, drainage systems, sight distances and anticipated future widening.
On-Street Parking Facilities
- On-street parking bays are designed as parallel or angled parking spaces from the curb.
- Parking configuration design factors, such as angle and number of bays, depend on available space area.
Off-Street Parking Facilities—Surface Car Parks
- Surface car parks are designed with both herringbone and traditional parking stall layouts.
- Features such as parking aisle design, space dimensions, and angles for cars relative to the pavement are included in illustrative diagrams.
Off-Street Parking Facilities—Garages
- Parking garages consist of multiple platforms/levels connected by access ramps.
- Ramps are engineered with gradients (1:10 for straight, and 1:12 for curved ramps).
- Ramp features, including radius and lane widths, are included.
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Description
Explore the critical components and principles of highway design, including cross-sectional elements and geometric classifications. This quiz focuses on understanding the dimensions and arrangements that optimize traffic efficiency and safety. Test your knowledge on these essential highway design features.
