Highway Design Principles Quiz

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Questions and Answers

What is the average daily traffic (ADT) classification for a highway with fewer than 200 vehicles?

Low Traffic (correct)

High Traffic

Moderate Traffic

Very High Traffic

What is the maximum superelevation (meters/meter) for highway design?

0.06

0.08 (correct)

0.09

0.07

What is required between the vehicle and a hazard when the driver can see the hazard?

There should be no other vehicles in the vicinity.

The distance should be greater than or equal to the stopping sight distance. (correct)

The distance must be equal to the driver's reaction time.

The stopping sight distance must be less than the vehicle speed.

Which of the following radius (meters) values is appropriate for flat topography with a design speed of 90 kph?

280 Signup and view all the answers

Which type of curve consists of two curves going in the same direction and should be avoided?

Broken back curves Signup and view all the answers

What is the recommended passing sight distance in meters for mountainous topography at a design speed of 50 kph?

360 Signup and view all the answers

What is the primary purpose of a transition curve in geometric design?

To introduce centrifugal force gradually for smooth turning. Signup and view all the answers

Which type of surfacing is not included in the highway design principles?

Reinforced asphalt Signup and view all the answers

What is a characteristic of compound curves in highway design?

They feature multiple curves connecting directly. Signup and view all the answers

What does 'R' represent in the equation for calculating distance to obstruction?

The radius of the curve. Signup and view all the answers

When considering a shoulder width in highway design, which value is typically utilized?

2.00 Signup and view all the answers

Which of the following is a goal of implementing a transition curve?

To improve the aesthetic appearance of the road. Signup and view all the answers

In rolling topography, what is the grade (percent) for a speed of 60 kph?

6.0 Signup and view all the answers

What defines obligatory points in highway alignment?

Points through which the highway must or must not pass. Signup and view all the answers

Which of the following curves requires separation for superelevation attainment?

Reverse curves Signup and view all the answers

What is the primary purpose of transition curves in horizontal alignment design?

To avoid abrupt changes in radius at high speeds Signup and view all the answers

Which factor is NOT a major consideration in horizontal alignment design?

Type of vehicle Signup and view all the answers

What does the term 'superelevation' refer to in highway design?

The difference in elevation between the outer and inner edges of a curve Signup and view all the answers

Which step is NOT part of the design of horizontal curves?

Design the vertical alignment Signup and view all the answers

Which of the following locations should not be crossed by highway alignments?

Religious places Signup and view all the answers

Which factor affects the maximum superelevation rate according to climate conditions?

Amount of ice and snow Signup and view all the answers

What type of interchange is characterized by a bridge structure that eliminates conflicts between through and crossing traffic?

Diamond Interchange Signup and view all the answers

What is the function of a spiral curve in horizontal alignment?

To provide a gradual change between tangents and curves Signup and view all the answers

What is the purpose of providing stopping sight distance throughout the length of a curve?

To ensure drivers can safely see obstacles Signup and view all the answers

Which interchange type uses weaving sections to eliminate all crossing movement conflicts?

Cloverleaf Interchange Signup and view all the answers

What distinguishes a Directional Interchange from other types of interchanges?

It permits direct paths for left turns. Signup and view all the answers

What is the primary purpose of a Trumpet Interchange?

To connect a terminating highway to a continuous highway. Signup and view all the answers

Which of the following statements about railway turnouts is correct?

They permit one track to cross another at grade. Signup and view all the answers

What is a key feature of an Overpass?

It crosses over another road or railway. Signup and view all the answers

What is the main limitation of having more switches in a railway network?

More potential disturbances to the railway network. Signup and view all the answers

What is the maximum allowable speed for a turnout with a length of 32 meters and a ratio of 1:9?

40 km/h Signup and view all the answers

What is the purpose of a vertical curve in roadway design?

To provide a gradual change in grade Signup and view all the answers

Which of the following is NOT a key issue to consider at level crossings?

Speed bumps Signup and view all the answers

Having a grade of 10% means that the elevation increases by how many feet for every 100 feet of horizontal distance?

10 feet Signup and view all the answers

Which turnout length allows for the highest maximum allowable speed?

99 meters Signup and view all the answers

Which factor is least affected by grades below 4-5%?

Passenger cars Signup and view all the answers

What best describes a major level/road crossing?

Located at major roads with at least four lanes Signup and view all the answers

What is a primary benefit of adequate sight distance in highway design?

Facilitates safe and efficient operation Signup and view all the answers

What does Stopping Sight Distance (SSD) primarily require?

Distance required to stop before reaching an object Signup and view all the answers

Which component is NOT included in the calculation of Stopping Sight Distance (SSD)?

Distance travelled during acceleration towards passing Signup and view all the answers

What is the primary purpose of Decision Sight Distance?

To perceive an unexpected condition and react accordingly Signup and view all the answers

What does Passing Sight Distance specifically account for?

Sufficient distance to perform a normal passing maneuver Signup and view all the answers

Which of the following is NOT part of the four distances used to determine passing sight distance?

Distance travelled during braking after an object is encountered Signup and view all the answers

What is a critical assumption made in the model used to calculate Passing Sight Distance?

The passing vehicle travels at a constant speed Signup and view all the answers

Which of the following best describes the time intervals represented in SSD?

Time for a driver to perceive, react, and stop Signup and view all the answers

What is the result of insufficient Passing Sight Distance on a two-lane highway?

Increased likelihood of head-on collisions Signup and view all the answers

Study Notes

Geometric Criteria for Highways and Railways

Principles of Geometric Design for Highways are based on minimum design standards for Philippine Highways, excluding tourism roads.
Average Daily Traffic (ADT) is used to determine design speed and radius.
Design speed varies based on topography (flat, rolling, mountainous).
Radius (in meters) also varies greatly based on topography.
Grade (percent) also fluctuates based on topography.
Pavement width (in meters), shoulder width, right of way width, and superelevation are also considered and vary based on topography.
Non-passing sight distance and passing sight distance also vary based on topography.
Type of surfacing varies as well.

General Principles for Geometric Design

Cross Section
Profile/Vertical Alignment
Alignment/Horizontal Alignment

Cross Section of Road and Rail Infrastructure

Shows a cross-section with dimensions for road and rail infrastructure.
Includes elements like pavement, shoulder, guardrail, median, tree, etc.
Also indicates ballast shoulder, Cess, etc.
Roadway and rail layers are shown (subsoil/natural ground, subgrade, formation, foundation, track, permanent way, sleepers, and rails, etc).

Straight, Circular Curve, and Transition

Straight: Shortest distance between two points with a constant bearing. Easy to design, set out, and maintain.
Circular Curve: Line with a fixed distance (radius) from a point. Constant force from train wheels, offset by cant/superelevation. Easy to design and maintain.
Transition: Curve with a constantly changing radius (spiral). Avoids instant change in radius, noticeable at high speeds.

Horizontal Geometric Design Considerations for Highways

Horizontal Alignment: Series of straight sections (tangents) connected by curves.
Major considerations include safety, grade profile, type of facility, design speed, and topography.
Construction cost is a consideration.
Key components for horizontal alignment include radius of curve, length of curve, superelevation, and widening.

Spiral Curve/Transition

Key steps for designing horizontal curves include determining a reasonable maximum superelevation rate, deciding upon a maximum side friction factor, calculating minimum radius, and iterating to satisfy design requirements.
Ensure the stopping sight distance is provided throughout the curve; adjust design as necessary.
Design the transition segments of the curve.

Cant/Superelevation

Difference in height between the outer and inner rail/road on a curve.
Gradually raises the outer rail/road. Controlled by factors: climate conditions, terrain, type of area, and frequency of slow-moving vehicles.
Typical rates and values include highest rates/values that do not increase slippage by stopped vehicles.

Superelevation

The superelevation of a highway cross-section and the side-friction factor.
Important components in designing horizontal curves.
Superelevation rate is the rise in the roadway surface elevation.
Example: 10% implies 1 ft rise for every 10 ft roadway width.

Side Friction

The side-friction factor is merely the coefficient of friction between the design vehicles’ tires and the roadway.
Depends on variables like pavement type and vehicle speed.

Minimum Curve Radius

Minimum radius for horizontal curves depends on the design speed, superelevation, and side friction factor.
It serves as a constraint and a starting point for a more thorough curve design.

Horizontal Sight Distance

Distance along the center line of the road where a driver can see an object.
Critical for curve design, as obstructions might obscure parts of the road. Calculations involve stopping sight distance and the distance between the centerline and the obstruction.

Horizontal Geometric Design Consideration for Highways

Horizontal alignment consists of straight sections connected by curves.
Curves are usually circular segments; radii are selected to provide a smooth and continuous traffic flow.

Simple curves with spirals, Broken Back, Compound curves, Reverse Curves, and transition curves

Various curve types are discussed to create a smooth driving experience.

Intersection (Interchanges)

Intersection: Area where two or more roads connect or cross.
Types such as underpasses, overpasses, trumpet interchanges, diamond interchanges, cloverleaf interchanges, and partial cloverleaf interchanges, and directional interchanges are discussed along with their characteristics.

Railway Turnouts and Crossing

Turnouts allow tracks to cross at grade.
Design may include movable center points for flexibility in the network.
Length, and maximum speed, to pass the turnout, are considerations in design.
Diagram shows the components for railway crossings such as Stock rails, Closure rails, Guard (check) rails, Point blades, Throw (tie) bar, and Frog.

Level Crossings

Level crossings allow road traffic to traverse railway lines at the same level.
Different types like major and minor level crossings with varying lanes.
Vertical clearance is discussed as a critical aspect.

General Principles for Vertical Curves

Grade: Measure of roadway inclination (slope).
Issues include safety and level of service, particularly for passenger cars and commercial vehicles.
Vertical curves (curves in vertical plane) connect gradients. They are designed to provide gradual change in grade to avoid abrupt changes or excessive gradients.
Sight distance: Essential for safe and efficient highway operation.
Headlight sight distance: Crucial for safely operating vehicles on highways at night.

Stopping (Non-Passing) Sight Distance (SSD)

Minimum distance required for a vehicle to stop safely before encountering an obstruction.
Assumes a design speed. Factors include perception, reaction time, and braking distance.
Assesses distance required to stop when traveling on wet pavement.

Decision Sight Distance (DSD)

Distance needed for a driver to detect, respond, and navigate an unexpected situation.
Factors like recognizing hazards, assessing conditions, and maneuvering vehicles safely are considered within this distance calculation.

Passing Sight Distance

Minimum distance required for vehicles to safely pass each other on two-lane highways.
Includes perception and reaction distance, initial maneuvering distance, and the distance traveled during acceleration on the left lane.

Distance Traversed by opposing vehicle during passing

Calculation for passing sight distance and assumptions needed for calculation.
Headlight Sight Distance- crucial for night driving without lighting as this determines the distance visible by headlights.

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Description

Test your knowledge on highway design principles, including average daily traffic classification, superelevation limits, and key geometric design concepts. This quiz covers essential aspects of highway engineering such as sight distance, transition curves, and curve types. Perfect for students or professionals in civil engineering.