Core Concepts for the Civil PE Exam:

Transportation Depth

 

Civil Morning Breadth and Transportation Depth Practice Problems and Quick Reference Manual

Ensure You're Prepared on Exam Day, With PE Core Concepts

PE Exam -Transportation Depth

  • Core Concepts Quick Reference guide breaking down the specific information needed for the PE Exam on every Breadth and Transportation depth topic from the NCEES Syllabus

  • 80 Civil Breadth practice problems with detailed solutions!

  • 40 Transportation Depth practice problems with detailed solutions!

  • Breakdown of relevant topics and example problems for all NCEES listed codes including AASHTO, AI, MUTCD, and HCM

  • Available in Paperback for $44.95 or access all of our Civil PE Exam practice questions Online Only for $24.99 

Civil PE Transportation Depth Online Study Guide
Click the topics below to expand the core concepts. This material is included in the Paperback edition

Traffic Engineering

Intersection Sight Distance


When a vehicle is approaching or is stopped at an intersection, they must have an adequate line of sight along the perpendicular roadway to be able to safely stop or maneuver if necessary. This sight distance can be approximated by sight triangles where the hypotenuse is the required sight distance and the base is the required stopping distance. The diagram below exhibits this where X is the stopping distance of the vehicle on the major road and H is the sight distance:




Interchanges


An interchange is a grade-separated crossing of 2 or more roadways in which ramps are used in such a manner so that the flow of traffic is not interrupted. On ramps and off ramps need to be designed such that there is enough length for acceleration and sight distance for the seamless merging of traffic. Mostly the design lengths can be determined from the appropriate tables in the GDHS.

There are a number of types of interchanges which have advantages and disadvantages based on the site constraints. Some examples include trumpet, diamond, partial and full cloverleaf, or fully directional

As with traffic signals, GDHS provides warrants for the consideration of the use of interchanges. These include:

1. Design Designation

2. Bottleneck or Spot Congestion Relief

3. Safety Improvements

4. Topography

5. User Benefits

6. Traffic Volume




At Grade Intersection Layout


Intersections must be detailed to minimize disruption of traffic and to ensure a safe driving condition. To achieve this, the layout must facilitate both proper sight distances and maneuverability. Acute angles at intersections provide difficulties for both of these aspects and should be avoided as much as possible. The AASHTO Policy on the Geometric Design of Highways and Streets (GDHS) provides a wide range of tables and figures. Chapter 2 focuses on vehicle dimensions and the ability to make turns. Chapter 9 provides guidance on the geometry of the traveled way and intersections to account for minimum turning requirements.





Horizontal Design

Forgiving Roadside Concepts


Drivers, for a number of reasons, may veer off the road whether it be distraction, fatigue, or to avoid collision. For proper roadway design, there needs to be a minimum horizontal distance so that the driver can safely return to the roadway unharmed. This horizontal distance which begins at the edge of the roadway is called the clear distance. The AASHTO Roadside Design Guide (RSDG) provides guidelines on the safety of cars which have traveled off of the roadway.

The land just outside of the roadway may not always be flat. The slope of the clear distance has an effect on the cars ability to safely recover. Slopes less than 1 Vertical to 4 Horizontal are considered recoverable slopes since the car’s ability to stop or maneuver will not be greatly affected by the slope. A non-recoverable slope is one which is steeper than 1:4. If a non-recoverable slope is present, the bottom of the slope must have a vehicle runout area which will allow the vehicle to stop. Table 3-1 of the AASHTO RSDG can be used to determine minimum clear distances based on slopes and design speeds.

When traveling on a horizontal curve, the cars traveling along the outside of the curve will struggle to recover more-so than a straight roadway due to the centrifugal force. Therefore, an adjustment factor needs to be applied to the clear zone on the outside of the curve only. The adjustment factor is found in table 3-2 of the AASHTO RSDG.




Barrier Design


Often objects outside of the roadway must fall within the clear zone. A barrier must be provided to both protect the object and prevent the vehicle from a collision. An appropriate barrier will minimize the damage to the vehicle and safely redirect it onto traffic. The runout length, LR, is the minimum distance away from an object that a vehicle may leave the roadway and strike the object. This will define the length of barrier needed. AASHTO RSDG Table 5-10b provides minimum values based on volume and design speeds. Barriers which are too close to the roadway may be troublesome to drivers and cause them to slow down. To prevent this, a minimum shy distance is provided in RSDG Table 5-7. The geometry of a barrier must be determined for a safe condition by the following equations:

LA = Distance from edge of road to back edge of object

b = Rise of taper slope

a = Run of taper slope

L1 = Length from object to beginning of flare

L2 = Distance from edge of road to face of barrier

LR = Runout Length

Crash attenuators can be used to prevent vehicles from crashing directly into an object or from entering an area which would be unsafe for the driver or pedestrians. When the vehicle strikes the attenuator, it begins to decelerate at a rate of the following equation:

d = Deceleration rate (ft/s2) v = Velocity (ft/s) L = Length of attenuator (ft) x = Attenuation efficiency factor The stopping force then is:

F = Stopping force (lbs)

w = weight of vehicle (lbs)

d = Deceleration rate

g = Force due to gravity (32.2 ft/s2)

SF = Safety factor




Cross Section Elements


While a roadway often has to fit the area and purpose of its proposed location, the geometric features must meet certain minimum and maximum values. The Policy on Geometric Design of Highways and Streets provides a large number of requirements for the design of a roadway or walkway cross section. For the PE exam it is best to become familiar with the location of these requirements and most importantly be able to find them quickly since it is unreasonable to be expected to memorize all values.




ADA Design Considerations


The American Disabilities Act of 1990 outlines the requirements for structures to ensure proper treatment of individuals with disabilities. The guidelines outline many topics including parking, ramps, egress and others and the requirements which must be met to ensure the proper accessibility and safety. For the PE exam you will likely be asked a question or two requiring you to lookup certain aspects of the code. You should not spend excessive amounts of time reading the code but be familiar with the sections and be able to navigate and find information quickly.





Vertical Design

Intersection Sight Distance


When a vehicle is approaching or is stopped at an intersection, they must have an adequate line of sight along the perpendicular roadway to be able to safely stop or maneuver if necessary. This sight distance can be approximated by sight triangles where the hypotenuse is the required sight distance and the base is the required stopping distance. The diagram below exhibits this where X is the stopping distance of the vehicle on the major road and H is the sight distance:




Interchanges


An interchange is a grade-separated crossing of 2 or more roadways in which ramps are used in such a manner so that the flow of traffic is not interrupted. On ramps and off ramps need to be designed such that there is enough length for acceleration and sight distance for the seamless merging of traffic. Mostly the design lengths can be determined from the appropriate tables in the GDHS.

There are a number of types of interchanges which have advantages and disadvantages based on the site constraints. Some examples include trumpet, diamond, partial and full cloverleaf, or fully directional

As with traffic signals, GDHS provides warrants for the consideration of the use of interchanges. These include:

1. Design Designation

2. Bottleneck or Spot Congestion Relief

3. Safety Improvements

4. Topography

5. User Benefits

6. Traffic Volume




At Grade Intersection Layout


Intersections must be detailed to minimize disruption of traffic and to ensure a safe driving condition. To achieve this, the layout must facilitate both proper sight distances and maneuverability. Acute angles at intersections provide difficulties for both of these aspects and should be avoided as much as possible. The AASHTO Policy on the Geometric Design of Highways and Streets (GDHS) provides a wide range of tables and figures. Chapter 2 focuses on vehicle dimensions and the ability to make turns. Chapter 9 provides guidance on the geometry of the traveled way and intersections to account for minimum turning requirements.





Intersection Geometry

Intersection Sight Distance


When a vehicle is approaching or is stopped at an intersection, they must have an adequate line of sight along the perpendicular roadway to be able to safely stop or maneuver if necessary. This sight distance can be approximated by sight triangles where the hypotenuse is the required sight distance and the base is the required stopping distance. The diagram below exhibits this where X is the stopping distance of the vehicle on the major road and H is the sight distance:




Interchanges


An interchange is a grade-separated crossing of 2 or more roadways in which ramps are used in such a manner so that the flow of traffic is not interrupted. On ramps and off ramps need to be designed such that there is enough length for acceleration and sight distance for the seamless merging of traffic. Mostly the design lengths can be determined from the appropriate tables in the GDHS.

There are a number of types of interchanges which have advantages and disadvantages based on the site constraints. Some examples include trumpet, diamond, partial and full cloverleaf, or fully directional

As with traffic signals, GDHS provides warrants for the consideration of the use of interchanges. These include:

1. Design Designation

2. Bottleneck or Spot Congestion Relief

3. Safety Improvements

4. Topography

5. User Benefits

6. Traffic Volume




At Grade Intersection Layout


Intersections must be detailed to minimize disruption of traffic and to ensure a safe driving condition. To achieve this, the layout must facilitate both proper sight distances and maneuverability. Acute angles at intersections provide difficulties for both of these aspects and should be avoided as much as possible. The AASHTO Policy on the Geometric Design of Highways and Streets (GDHS) provides a wide range of tables and figures. Chapter 2 focuses on vehicle dimensions and the ability to make turns. Chapter 9 provides guidance on the geometry of the traveled way and intersections to account for minimum turning requirements.





Roadside and Cross Section Design

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Signal Design

Signs and Pavement Markings


MUTCD Chapter 3 provides requirements for signs and pavement markings. As with cross sectional elements, become familiar with this chapter and how to locate requirements quickly.




Temporary Traffic Control


When work in the roadway is necessary, traffic must be shifted and directed away from the work zone in a safe manner for both the flow of traffic and the workers in the zone of construction. Tapered traffic control devices are used to direct traffic away from the work zone. MUTCD provides equations for the suggested taper length.

W = Width of work zone

S = Design speed (mph)

However, the length L must be adjusted depending on the type of taper as per MUTCD Table 6C-3.





Traffic Control Design

Signs and Pavement Markings


MUTCD Chapter 3 provides requirements for signs and pavement markings. As with cross sectional elements, become familiar with this chapter and how to locate requirements quickly.




Temporary Traffic Control


When work in the roadway is necessary, traffic must be shifted and directed away from the work zone in a safe manner for both the flow of traffic and the workers in the zone of construction. Tapered traffic control devices are used to direct traffic away from the work zone. MUTCD provides equations for the suggested taper length.

W = Width of work zone

S = Design speed (mph)

However, the length L must be adjusted depending on the type of taper as per MUTCD Table 6C-3.





Geotechnical and Pavement

Signs and Pavement Markings


MUTCD Chapter 3 provides requirements for signs and pavement markings. As with cross sectional elements, become familiar with this chapter and how to locate requirements quickly.




Temporary Traffic Control


When work in the roadway is necessary, traffic must be shifted and directed away from the work zone in a safe manner for both the flow of traffic and the workers in the zone of construction. Tapered traffic control devices are used to direct traffic away from the work zone. MUTCD provides equations for the suggested taper length.

W = Width of work zone

S = Design speed (mph)

However, the length L must be adjusted depending on the type of taper as per MUTCD Table 6C-3.





Drainage

Intersection Sight Distance


When a vehicle is approaching or is stopped at an intersection, they must have an adequate line of sight along the perpendicular roadway to be able to safely stop or maneuver if necessary. This sight distance can be approximated by sight triangles where the hypotenuse is the required sight distance and the base is the required stopping distance. The diagram below exhibits this where X is the stopping distance of the vehicle on the major road and H is the sight distance:




Interchanges


An interchange is a grade-separated crossing of 2 or more roadways in which ramps are used in such a manner so that the flow of traffic is not interrupted. On ramps and off ramps need to be designed such that there is enough length for acceleration and sight distance for the seamless merging of traffic. Mostly the design lengths can be determined from the appropriate tables in the GDHS.

There are a number of types of interchanges which have advantages and disadvantages based on the site constraints. Some examples include trumpet, diamond, partial and full cloverleaf, or fully directional

As with traffic signals, GDHS provides warrants for the consideration of the use of interchanges. These include:

1. Design Designation

2. Bottleneck or Spot Congestion Relief

3. Safety Improvements

4. Topography

5. User Benefits

6. Traffic Volume




At Grade Intersection Layout


Intersections must be detailed to minimize disruption of traffic and to ensure a safe driving condition. To achieve this, the layout must facilitate both proper sight distances and maneuverability. Acute angles at intersections provide difficulties for both of these aspects and should be avoided as much as possible. The AASHTO Policy on the Geometric Design of Highways and Streets (GDHS) provides a wide range of tables and figures. Chapter 2 focuses on vehicle dimensions and the ability to make turns. Chapter 9 provides guidance on the geometry of the traveled way and intersections to account for minimum turning requirements.





Engineering Economics

Signs and Pavement Markings


MUTCD Chapter 3 provides requirements for signs and pavement markings. As with cross sectional elements, become familiar with this chapter and how to locate requirements quickly.




Temporary Traffic Control


When work in the roadway is necessary, traffic must be shifted and directed away from the work zone in a safe manner for both the flow of traffic and the workers in the zone of construction. Tapered traffic control devices are used to direct traffic away from the work zone. MUTCD provides equations for the suggested taper length.

W = Width of work zone

S = Design speed (mph)

However, the length L must be adjusted depending on the type of taper as per MUTCD Table 6C-3.





 
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