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Questions and Answers
What term is generally understood to refer to the number of vehicles passing through in units of vehicles per hour?
What term is generally understood to refer to the number of vehicles passing through in units of vehicles per hour?
Volume
What is the formula for traffic flow (q) in terms of the number of vehicles passing through (n) and the duration of the time interval (t)?
What is the formula for traffic flow (q) in terms of the number of vehicles passing through (n) and the duration of the time interval (t)?
q = n / t
What does the term 'time headway' refer to in traffic analysis?
What does the term 'time headway' refer to in traffic analysis?
The time between the passage of the front bumpers of successive vehicles
What is the formula for time mean speed (μt) in terms of observed speeds of individual vehicles?
What is the formula for time mean speed (μt) in terms of observed speeds of individual vehicles?
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What does the term 'jam density' refer to in traffic flow analysis?
What does the term 'jam density' refer to in traffic flow analysis?
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What is the formula for traffic flow at capacity (qc) in a parabolic flow-density model?
What is the formula for traffic flow at capacity (qc) in a parabolic flow-density model?
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How is the space-mean speed (μs) calculated using the linear speed-density relationship?
How is the space-mean speed (μs) calculated using the linear speed-density relationship?
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Study Notes
Traffic Analysis
- Traffic flow is often measured over an hour, and the resulting value is referred to as volume (vehicles per hour, veh/h).
Traffic Flow Calculation
- _traffic flow (q) = number of vehicles (n) / duration of time interval (t)
- average time headway (ℏ) = Σhi / n, where hi is the time headway of the ith vehicle
Average Speeds
- Time-mean speed (𝜇𝑡) = Σui / n, where ui is the observed speed of the ith vehicle
- Space-mean speed (𝜇𝑠) = Σdi / Σti, where di is the length of the roadway section and ti is the observed time for the ith vehicle to travel the section
Density and Speed
- Density (k) can be related to individual spacing between successive vehicles
- k = n / d, where d is the length of the roadway section
- The increase in traffic density affects the average operating speed of vehicles, eventually leading to jam density
Speed-Density Relationship
- The linear speed-density relationship is given by 𝜇𝑠 = 𝜇𝑓 (1 - k / kj), where 𝜇𝑓 is the free-flow speed and kj is the jam density
- The parabolic flow-density model is given by q = 𝜇𝑓 (k - k² / kj)
Traffic Flow at Capacity
- Traffic flow at capacity (qc) is the highest rate of traffic flow the highway can handle
- qc corresponds to a specific traffic density (kc) and speed (uc)
Calculating Speeds and Densities
- Examples of calculating time-mean and space-mean speeds, average speed of traffic, and space-mean speed from given data are provided.
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Description
This quiz covers the concepts of traffic analysis, variables of traffic flow, and relationships between traffic fundamentals. It also explores the measurement of traffic flow and volume.
