Traffic Survey Methods Overview

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Questions and Answers

What is the main limitation of the floating car method for surveying traffic?

It only surveys cars. (correct)

It can measure pedestrian traffic.

It requires extensive road closures.

It is entirely random in vehicle selection.

What is necessary for the survey car to accurately record time and delays?

Knowledge of all routes beforehand.

Continuous traffic light monitoring.

An advanced GPS system.

Pre-determined timing points. (correct)

What should be included in a comprehensive traffic survey?

Only one route to minimize complexity.

Residential streets only.

Only major highways.

All main road networks and minor roads. (correct)

What is the purpose of pilot surveys in traffic data collection?

To familiarize staff and test routes. Signup and view all the answers

What is a suggested speed for the survey car while recording traffic data?

15 km/h to match typical traffic speeds. Signup and view all the answers

What is critical for measuring distance between timing points in the survey?

Using a measuring wheel or a good quality map. Signup and view all the answers

How are survey links for a traffic study determined?

Including various main and minor roads. Signup and view all the answers

What is a challenge faced when selecting vehicles to follow during surveys?

The vehicle routes are unknown in advance. Signup and view all the answers

What type of data is typically presented in a Journey Time/Moving Observer Delay Survey?

Travel time and speed Signup and view all the answers

Why might simple averages give biased results in journey time surveys?

They reflect conditions at different times of day Signup and view all the answers

What is necessary to produce an accurate average competitive human resource during a journey time survey?

Ensuring equal dispatch intervals Signup and view all the answers

How can travel times for each link or route be effectively compared?

By time of day and corresponding traffic flow Signup and view all the answers

What is one potential advantage of conducting multiple runs during a journey time survey?

It enables a broader understanding of travel delay patterns Signup and view all the answers

What could be a consequence of making a car dispatch too frequent during data collection?

Misrepresentation of average travel speeds Signup and view all the answers

Which of the following actions could improve the reliability of journey time surveys?

Balancing dispatch times across peak and off-peak hours Signup and view all the answers

What should be considered to minimize delays during a pilot survey?

Dispatching cars at equal intervals that exceed the longest circuit time Signup and view all the answers

What does junction delay measure in urban traffic?

The extra journey time vehicles incur when impeded Signup and view all the answers

What is the primary purpose of using the 'floating car method' or registration plate matching survey?

To evaluate delay when queues extend back to the next major junction Signup and view all the answers

What is typically measured during a Junction Delay Survey?

The number of stopped vehicles at fixed intervals Signup and view all the answers

How is average delay calculated according to the 'Short-Base' method?

By dividing total delay by traffic volume Signup and view all the answers

What alternative method is suggested for classifying vehicles at a junction if the queue cannot be fully counted?

Elevated Observer Method Signup and view all the answers

Which vehicle classes should be used during a delay survey?

A maximum of three vehicle classes consistently across delay and flow measurements Signup and view all the answers

What duration of time is typically used for counting during a junction delay survey?

5 or 10 minutes Signup and view all the answers

What is the recommended duration for observation during a delay survey?

5 to 10 minutes Signup and view all the answers

In conducting a Junction Delay Survey, how is the roadway area typically divided for counting stopped vehicles?

Into boxes small enough for continuous counting Signup and view all the answers

What represents a common technique for determining junction performance?

Average delay per vehicle Signup and view all the answers

What should the observation interval be during a delay survey?

Between 10 and 30 seconds, not an exact factor of any signal cycle time Signup and view all the answers

What is the purpose of conducting a junction delay survey before and after an improvement?

To compare junction performance and improvements Signup and view all the answers

Why are non-motorized vehicles typically excluded from delay surveys?

They do not affect motor vehicle flow significantly Signup and view all the answers

Which of the following statements is true regarding the observation interval in delay surveys?

It must remain consistent throughout the survey for all approaches Signup and view all the answers

What key aspect should a surveyor consider when checking the counting distance in a junction delay survey?

Distance should be at least 10 meters beyond the longest queue Signup and view all the answers

What type of vehicles is typically focused on during delay surveys according to the outlined methods?

Motorized vehicles, excluding non-motorized vehicles Signup and view all the answers

What is essential for conducting the survey on multiple approaches simultaneously?

Delays related to the approaches must be surveyed at the same time. Signup and view all the answers

How is the total delay in vehicle hours calculated during the survey?

By counting the total number of queueing vehicles and multiplying by average travel delay. Signup and view all the answers

What should be the minimum distance for the start timing point from the longest anticipated queue?

10 metres Signup and view all the answers

Which vehicle classifications can the calculations of delay be made separately from?

Vehicle class, turning movement, or time period. Signup and view all the answers

Where should the pilot survey be conducted for testing procedures?

During the most congested time of the proposed survey. Signup and view all the answers

What is the purpose of the finish timing point in the survey?

To define the exit from the junction or stop line. Signup and view all the answers

Which factor is NOT necessary when identifying timing points for the survey?

Should be marked with appropriate signage. Signup and view all the answers

What determines the average undelayed travel time in the delay calculations?

The travel times of vehicles categorized as undelayed. Signup and view all the answers

Study Notes

Floating Car Method Limitations

Main Limitation: The floating car method can be significantly affected by the survey car's driving behavior, particularly if the driver is not experienced or if there are distractions.

Accurate Time and Delay Recording

Survey Car Requirements: To accurately record time and delays, the survey car needs a reliable clock to mark the entry and exit times at various points along the route.

Comprehensive Traffic Survey Components

Necessary Components: A comprehensive traffic survey should include data on traffic volumes, journey times, speeds, and delays.

Pilot Surveys

Purpose: Pilot surveys play a crucial role in traffic data collection by helping refine data collection procedures, identify potential issues, and optimize survey design.

Survey Car Speed

Recommended Speed: A suggested speed for the survey car during data recording is the prevailing speed of the traffic flow.

Measuring Distance

Critical Requirement: Accurately measuring the distance or length between timing points is essential for effective data analysis.

Determining Survey Links

Link Determination: Survey links in a traffic study are usually defined by the road sections that connect timing points, such as intersections or other significant points on the route.

Challenges in Vehicle Selection

Vehicle Selection Challenge: A challenge in selecting vehicles to follow during surveys is ensuring the chosen vehicles represent the general traffic composition and typical speeds.

Journey Time/Moving Observer Delay Survey Data

Typical Data: Journey time/moving observer delay surveys typically present data on average vehicle speeds, journey times, delays experienced by the survey car, and traffic flow characteristics.

Simple Averages and Biased Results

Average Bias: Simple averages in journey time surveys can be biased, especially when the survey car's travel patterns don't reflect the typical journeys of the majority of vehicles on the road.

Accurate Average Competitive Human Resource

Requirement for Accuracy: To produce an accurate average competitive human resource during a journey time survey, it's crucial to have a large enough sample size and ensure the selected survey vehicles accurately represent the general traffic population

Comparing Travel Times

Effective Comparison: For effective comparison of travel times for each link or route in a journey time survey, it's important to analyze the data based on vehicle classifications and time periods.

Multiple Runs in Journey Time Surveys

Potential Advantage of Multiple Runs: Conducting multiple runs during a journey time survey can provide more robust data, leading to greater reliability when assessing average travel times.

Frequent Car Dispatch

Consequence of Frequent Dispatch: Dispatching survey cars too frequently during data collection can potentially disrupt traffic flow and introduce undesirable bias into the data.

Improving Journey Time Survey Reliability

Actions to Improve Reliability: Actions that can improve the reliability of journey time surveys include using experienced drivers, ensuring consistent survey methodologies, and implementing robust data quality checks.

Minimizing Delays in Pilot Surveys

Delay Minimization Strategies: To minimize delays during a pilot survey, selecting a less congested time period, using a familiar route, and avoiding peak traffic hours are important considerations.

Junction Delay - Urban Traffic

Measurement: Junction delay in urban traffic measures the extra time vehicles spend stopped or maneuvering at intersections due to congestion.

'Floating Car Method' or Registration Plate Matching

Primary Purpose: The 'floating car method' or registration plate matching survey aims to collect data on journey times, delays, and traffic flow patterns on a specific route.

Junction Delay Survey - Measurements

Typical Measurements: A junction delay survey typically measures stopped vehicles at intersections, the delay experienced by vehicles, and traffic volumes at the junction.

'Short-Base' Method for Calculating Average Delay

Calculation Method: The 'Short-Base' method calculates average delay by dividing the total stopped vehicle-hours by the total number of vehicles entering the junction during the observation period.

Alternative Vehicle Classification at Junctions

Alternative Method: If the queue cannot be fully counted at a junction, an alternative method for classifying vehicles involves estimating the proportions of different vehicle types based on observed traffic flows.

Vehicle Classes in Delay Surveys

Relevant Vehicle Classes: Vehicle classes that should be used during a delay surveys include cars, heavy goods vehicles (HGVs), and buses.

Counting Duration in Junction Delay Surveys

Typical Counting Duration: Junction delay surveys typically use a counting duration of 15 minutes, providing a reasonably representative sample of traffic

Observation Duration in Delay Surveys

Recommended Observation Duration: A recommended observation duration for a delay survey, if possible, is 30 minutes, allowing for the capture of traffic flow fluctuations and a more representative sample of data.

Roadway Division for Counting

Roadway Area Division: In a junction delay survey, the roadway area is typically divided into lanes for counting stopped vehicles.

Determining Junction Performance

Technique for Determination: A common technique for determining junction performance is the use of delay surveys.

Observation Interval During Delay Surveys

Observation Interval: The observation interval during a delay survey is typically set at 15 seconds, ensuring a balance between capturing traffic dynamics and minimizing observer fatigue.

Junction Delay Surveys Before and After Improvement

Survey Purpose: Conducting a junction delay survey before and after an improvement allows for a quantifiable evaluation of the effectiveness of the modification in reducing congestion and delay.

Exclusion of Non-Motorized Vehicles

Reason for Exclusion: Non-motorized vehicles like bicycles and pedestrians are typically excluded from delay surveys because their delay measurements are not relevant to the study's focus on vehicular flow.

Observation Interval in Delay Surveys

Truth Regarding Observation Interval: The observation interval in delay surveys can vary depending on the study objectives, the level of detail required, and the traffic conditions being observed.

Counting Distance in Delay Surveys

Surveyor Consideration: When checking the counting distance in a junction delay survey, surveyors should consider the distance of the longest anticipated queue to ensure all stopped vehicles are accurately counted.

Vehicle Focus in Delay Surveys

Vehicle Focus: Delay surveys typically focus on passenger vehicles, HGVs, and buses, recognizing their contribution to the overall delay experienced at junctions.

Conducting Simultaneous Surveys

Essential Requirement: Conducting simultaneous surveys on multiple approaches to a junction is essential for accurately capturing the delay experienced by all vehicles entering the junction. .

Total Delay Calculation

Delay Calculation: The total delay in vehicle hours during a survey is calculated by multiplying the average delay per vehicle (in hours) by the total number of vehicles entering the junction..

Start Timing Point Distance

Minimum Distance: The minimum distance for the start timing point from the longest anticipated queue should be sufficient to ensure that the survey car captures the full extent of the queue.

Separate Delay Calculations

Vehicle Classifications: Delay calculations can be made separately for different vehicle classifications like cars, HGVs, and buses, allowing for a more detailed analysis of the impact of different vehicle types

Pilot Survey Location

Location Choice: The pilot survey should be conducted on a representative section of the road where the procedures and equipment can be adequately tested.

Finish Timing Point Purpose

Purpose: The finish timing point serves as the endpoint for measuring journey times and delays, enabling the calculation of travel statistics for the survey route.

Identifying Timing Points

Non-Necessary Factor: When identifying timing points for the survey, the direction of the traffic flow is not a necessary factor for accurate time and delay measurements.

Average Undelayed Travel Time

Determination: The average undelayed travel time in the delay calculations is determined by dividing the total distance of the survey link by the average speed of uninterrupted traffic flow during the observation period.

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Description

This quiz covers various methods of conducting traffic surveys, including the Floating Car Method, Journey Time Surveys, and Junction Delay Surveys. It discusses the strengths and weaknesses of these methods, as well as essential considerations for obtaining accurate traffic data. Dive into the intricacies of traffic analysis and learn how to effectively measure and interpret travel patterns.