Podcast
Questions and Answers
What is the design volume in highway construction?
The design volume is the number of vehicles estimated to pass a road towards the end of its life.
What is the minimum life commonly assumed for flexible pavement?
Which of the following is NOT an element to include in design traffic data?
What percentage does the average T (trucks) represent of DHV on main rural highways?
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The design traffic data for highways should include ADT, DHV, and __________.
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What is the typical range for the ratio of DHV to ADT for rural areas?
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Match the elements of traffic volume estimation with their definitions:
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What is the design volume in highway construction?
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What is the assumed minimum life for a flexible pavement in highway design?
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What does ADT stand for in traffic design data?
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What is the typical percentage range of K, the ratio of DHV to ADT, for rural areas?
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The design traffic data should only include average daily traffic (ADT).
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The _____ should be designed to accommodate a projected number of vehicles over its lifespan.
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What is T in the context of design traffic data?
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What percentage does D typically vary from in two-way design hourly volume?
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An example of a peak hour traffic count might show the volume of traffic during the 6:00-6:15 pm period as _____ vehicles.
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Study Notes
Design Volume
- A road should be designed to accommodate the number of vehicles expected to use it towards the end of its lifespan.
- This estimated number is called the design volume.
- The minimum lifespan is generally assumed to be 10 to 15 years for flexible pavement and 20 years for rigid pavement.
- The design traffic data should include:
- ADT (Average Daily Traffic) for both current and future years.
- DHV (Design Hourly Volume), covering a two-way flow unless specified otherwise.
- K, representing the ratio of Design Hourly Volume to Average Daily Traffic, typically ranging from 12% to 18% in rural areas and 8% to 12% in urban areas.
- D, indicating the directional distribution of Design Hourly Volume, with the volume in the predominant travel direction expressed as a percentage of the total.
- T, representing the percentage of trucks (excluding light delivery trucks) within the Design Hourly Volume.
Example: Estimating Peak Hour Volume
- The table displays 15-minute volume counts during the peak hour on an approach to an intersection.
- The highest volume occurs during the 6:30 PM to 6:45 PM time slot, with a count of 412 vehicles.
- This highest volume, 412 vehicles, would be considered the Peak Hour Volume.
Design Controls of Highway Construction
- Design volume is the number of vehicles a road should be able to accommodate at the end of its lifespan, typically 10-15 years for flexible pavement and 20 years for rigid pavement.
- Anticipated Traffic Volume is a key factor in highway design.
- The minimum design life for a road is 10 to 15 years for flexible pavements and 20 years for rigid pavements.
- ADT (Average Daily Traffic) is a measure of the average number of vehicles that travel on a road each day.
- ADT includes both current and future traffic estimates, specified by year.
- DHV (Design Hourly Volume) is the maximum anticipated two-way traffic volume in an hour.
- DHV is typically 30% of the ADT
- The K value is the ratio of DHV to ADT.
- For rural roads, K is 12%-18%, while for urban roads it's 8%-12%.
- D (Directional Distribution) accounts for the percentage of the DHV traveling in a specific direction.
- D typically ranges from 50% to 80%, with an average of 67% in the predominant travel direction.
- T (Truck Traffic) is the percentage of trucks (excluding light delivery trucks) in the DHV.
- Main rural highways typically have 7-9% T in the DHV and 13% in the ADT.
- Weekend peaks could lower the average T to 5%-8% of the DHV.
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Description
Explore the fundamental concepts of design volume in transportation engineering. This quiz covers key terms such as Average Daily Traffic (ADT), Design Hourly Volume (DHV), and important ratios affecting traffic design. Test your knowledge on traffic data estimation for effective road design.
