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MODULE 3
LEARNING OBJECTIVES
The following gives an overview of the learnings need to be achieved for this module.1. Describe vital concepts related to traffic streams.
The following gives an overview of the learnings need to be achieved for this module.1. Describe vital concepts related to traffic streams.
EVIDENCE OF LEARNING
Salazar_BSCE2B_Classwork Assignment #1.pdfTRAFFIC FLOW FUNDAMENTALS
The document above which is our classwork assignment summarizes the fundamentals of traffic flow such as the types of flows, the traffic variables, as well as the relationship between flow, density, and speed. It provides an outline of the vital concepts related to traffic streams. For convenience, a detailed discussion of the aforementioned topics and the content of the document is provided below. "Traffic flow fundamentals provide a systematic understanding of how vehicles move and interact within transportation networks." In other words, understanding the traffic flow fundamentals helps us to comprehend the dynamics and interactions of vehicles. The movement of vehicles on highways is referred to as traffic flow, and understanding its behavior is critical for successful traffic management, congestion mitigation, and road safety. Transportation experts may design strategies to optimize traffic operations, boost mobility, and improve the overall performance of transportation systems by examining traffic flow characteristics.
Basically, there are two types of traffic flows and it is evident from the evidence of learning presented above, namely, the uninterrupted traffic flow, and the interrupted traffic flow. Uninterrupted traffic flow is the flow occurring at long sections of roads where vehicles are not required to stop by any cause external to the traffic stream, whereas, interrupted traffic flow is the flow occurring at intersections or roadways where vehicles are required to stop by any reason outside the traffic stream like traffic signs or signal lights. For instance, uninterrupted traffic flow occurs when cars can go smoothly and continuously, as is common on freeways, expressways, and less crowded routes. Vehicles in continuous flow go at a generally constant speed and spacing, with little pauses or delays. Interrupted traffic flow, on the other hand, occurs in metropolitan regions or places with high traffic density, when cars meet disturbances, delays, and interruptions. There is traffic control equipment present, such as traffic lights and junctions, which causes speed variations, temporary pauses, and frequent encounters between cars. For better comparison, I created the summarized diagram on the left where key phrases are utilized.
In order to fully understand the complexity of traffic flow, one must be familiar of its variables. There are three major traffic variables, namely, flow rate or volume, speed, and density or concentration. Additionally, there are other variables that are used to describe traffic flow such as time headway, spacing, and time occupancy.
- Flow Rate or Volume: Flow rate indicates the number of vehicles that pass through a specific point on a road within a given time period. It is a fundamental metric for assessing traffic and determining road capacity. Flow rate data is crucial for managing traffic, analyzing capacity, and planning infrastructure.
- Speed: Speed denotes the rate at which vehicles travel. It is a vital variable that impacts safety, efficiency, and travel time. Analyzing speed enables the evaluation of traffic flow quality, identification of potential speed-related hazards, and assessment of roadway performance.
- Density or Concentration: Density or concentration refers to the number of vehicles occupying a specific length of road at a particular time. It is measured as vehicles per unit length, such as vehicles per mile or kilometer. Density provides insights into congestion levels and the utilization of roadway capacity.
- Time Headway: Time headway represents the time gap between consecutive vehicles traveling in the same lane. It is the time elapsed between the front bumper of one vehicle passing a point and the following vehicle passing the same point. Time headway is a significant indicator of traffic flow stability, driver behavior, and the potential for rear-end collisions.
- Spacing: Spacing indicates the physical distance between successive vehicles traveling in the same lane. It measures the gaps or intervals between vehicles. Analyzing spacing helps evaluate traffic congestion levels, assess roadway capacity, and understand vehicle interactions.
- Time Occupancy: Time occupancy reflects the proportion of time a specific point on a road is occupied by vehicles within a given time period. It measures the duration that vehicles spend in a particular location, such as a road section or during a traffic signal cycle. Time occupancy is valuable for assessing traffic flow characteristics, optimizing signal timing, and evaluating intersection performance.
In traffic analysis, understanding the relationships between speed, density, and flow is critical for successful transportation planning, traffic management, and route design. These interactions offer important information about how traffic conditions change and interact within a roadway network. Transportation experts may get a thorough understanding of traffic behavior and make educated judgments to maximize road capacity, increase safety, and improve overall traffic flow by investigating the speed-density, flow-density, and speed-flow relationships. The speed-density relation refers to how the speed of vehicles changes as the density or concentration of vehicles on a roadway varies. When there are fewer vehicles on the road, the traffic density is low, and vehicles can generally travel at higher speeds with less congestion. However, as more vehicles enter the roadway and the density increases, traffic tends to slow down. This slowdown occurs because the increased number of vehicles leads to more interactions and closer spacing between vehicles, which reduces the available space for each vehicle to maneuver. As a result, congestion builds up, and the average speed of vehicles decreases. See the first graph on the left. Additionally, the flow-density relation which is presented by the second graph examines how the flow rate or volume of vehicles passing through a given point on a roadway changes with variations in traffic density. As traffic density increases, the flow rate typically rises initially. This increase occurs because when the density is low, there is ample space between vehicles, allowing for a greater number of vehicles to pass through a point in a given time. However, at a certain point, known as the capacity of the roadway, further increases in density lead to decreased flow rates. This is because the roadway becomes saturated with vehicles, causing congestion and limiting the capacity to accommodate more vehicles. Beyond this capacity point, as the density continues to increase, the flow rate decreases due to the reduced ability of vehicles to move freely. Furthermore, the speed-flow relation examines how the average speed of vehicles changes as the flow rate or volume of vehicles on a roadway varies. As the flow rate increases, meaning more vehicles are on the road, the average speed of vehicles tends to decrease. This decrease occurs because the increased number of vehicles leads to more congestion and interactions, resulting in slower overall traffic flow. On the other hand, when the flow rate decreases, meaning fewer vehicles are on the road, the average speed of vehicles tends to increase. With fewer vehicles, there is less congestion, and vehicles can travel more freely, leading to higher average speeds. This is evident on the third graph on the left.
To sum things up, the speed-density relation refers to the relationship between the speed of vehicles and the density or concentration of vehicles on a roadway. Generally, as the density of vehicles increases, the speed of traffic tends to decrease due to congestion and increased interaction between vehicles. Meanwhile, the flow-density relation pertains to the relationship between the flow rate or volume of vehicles and the density of vehicles on a roadway. As the density of vehicles increases, the flow rate initially rises until reaching a maximum point, known as the capacity of the roadway. Beyond this point, further increases in density lead to decreased flow rates due to congestion and reduced ability for vehicles to move freely. Lastly, the speed-flow relation describes the relationship between the speed of vehicles and the flow rate or volume of vehicles on a roadway. In general, as the flow rate increases, the average speed of vehicles tends to decrease due to increased traffic and congestion. At the same time, as the flow rate decreases, the average speed of vehicles tends to increase as there is less interaction and congestion on the roadway. Knowing these information, how do we apply the queuing theory?
In addition to the information provided in the evidence of learning, I would like to add further information about Queuing Theory. Queuing theory from the term itself, is used to analyze the performance of waiting lines or queues. According to the University of Idaho (n.d.), queuing theory can be used to analyze the traffic flow on the approach to and through an intersection controlled by a traffic signal. The analysis involves studying the cumulative movement of vehicles over time. To visualize this, a queuing diagram can be created to represent the flow of vehicles on one approach to the intersection. In the case of interrupted flow, the queuing diagram illustrates the traffic flow on a specific intersection approach. During the red signal interval, which occurs between time t1 and t2, traffic is completely stopped. When the green signal interval begins at time t2, vehicles start departing from the intersection at the saturation flow rate, represented as qG. This flow continues until the queue of waiting vehicles is completely cleared. Once the queue is exhausted, the departure rate, denoted as D(t), matches the arrival rate, denoted as A(t), until time t3, which marks the beginning of the next red signal interval. At this point, the entire process repeats itself with a new cycle.
Queuing theory seemed to be so complex but contributes significantly to traffic flow evaluation by providing a systematic framework for quantitatively analyzing performance, optimizing resource allocation, planning capacity, fine-tuning traffic signals, and conducting simulation and scenario analysis. This theory enables transportation engineers to understand system efficiency, make sound judgments, improve flow and operation, and devise efficient traffic management techniques. Experts get significant insights into the dynamics of traffic queues by applying queuing theory, allowing them to optimize many parts of transportation systems and construct more efficient and reliable networks.
REFLECTION
When this topic was introduced to us in a face-to-face discussion, I found it easy to understand because the majority of the topics were conceptual and probably because the topics themselves were easy. For instance, I can summarize all the discussed topics in my own words. Traffic flow or simply the movement of vehicles on roadways has two types, uninterrupted, and interrupted traffic flow. Uninterrupted traffic flow, from the term itself, pertains to no interruptions flow or "smooth" traffic flow because no traffic control devices are present such as in freeways and expressways. On the other hand, interrupted traffic flow has delays and interruptions because of the traffic control devices that cause variations in speeds and temporary stops. This is very evident in urban areas such as in crowded cities or more specifically the majority of roads in Manila which was recently ranked as the eighth most congested city in the world. Furthermore, there are traffic variables that will help us fully understand the concept of traffic flow, namely, flow rate or volume, speed, density or concentration, time headway, spacing, and time occupancy. Flow rate or volume is the number of vehicles that passed a point on a roadway at a time range. Speed answers how fast the vehicles travel. Density or concentration is the number of vehicles on a roadway length at a specific time. Time headway is simply the time interval between consecutive vehicles passing a specific point. Spacing is basically the physical distance between successive vehicles. Lastly, time occupancy is the total time a point on the roadway is occupied by vehicles within a time period. Moreover, speed and density have an inverse relationship while the speed-flow and flow-density relationships have variations because when a certain maximum is reached, the relationship of the variables reverses. Generally, studying the fundamentals of traffic flow helped me understand how vehicles behave on a roadway and somewhat gave me valid reasons why a certain road is always congested and why road accidents happen. Also, I already realized why students or even employees blame the traffic once they came or arrived late to their destinations. It is valid to reason out traffic especially when you have spent an hour being stuck on your vehicle. Though it is a must to anticipate traffic especially when you have important matters to do, I found it very unsympathetic to blame the person for being late. Spending an hour or more on the road is a waste of time. You could have spent it with your friends, family, or your study. The traffic situation in the country is very alarming and I think something must be done to improve it or at least minimize congestion.
When this topic was introduced to us in a face-to-face discussion, I found it easy to understand because the majority of the topics were conceptual and probably because the topics themselves were easy. For instance, I can summarize all the discussed topics in my own words. Traffic flow or simply the movement of vehicles on roadways has two types, uninterrupted, and interrupted traffic flow. Uninterrupted traffic flow, from the term itself, pertains to no interruptions flow or "smooth" traffic flow because no traffic control devices are present such as in freeways and expressways. On the other hand, interrupted traffic flow has delays and interruptions because of the traffic control devices that cause variations in speeds and temporary stops. This is very evident in urban areas such as in crowded cities or more specifically the majority of roads in Manila which was recently ranked as the eighth most congested city in the world. Furthermore, there are traffic variables that will help us fully understand the concept of traffic flow, namely, flow rate or volume, speed, density or concentration, time headway, spacing, and time occupancy. Flow rate or volume is the number of vehicles that passed a point on a roadway at a time range. Speed answers how fast the vehicles travel. Density or concentration is the number of vehicles on a roadway length at a specific time. Time headway is simply the time interval between consecutive vehicles passing a specific point. Spacing is basically the physical distance between successive vehicles. Lastly, time occupancy is the total time a point on the roadway is occupied by vehicles within a time period. Moreover, speed and density have an inverse relationship while the speed-flow and flow-density relationships have variations because when a certain maximum is reached, the relationship of the variables reverses. Generally, studying the fundamentals of traffic flow helped me understand how vehicles behave on a roadway and somewhat gave me valid reasons why a certain road is always congested and why road accidents happen. Also, I already realized why students or even employees blame the traffic once they came or arrived late to their destinations. It is valid to reason out traffic especially when you have spent an hour being stuck on your vehicle. Though it is a must to anticipate traffic especially when you have important matters to do, I found it very unsympathetic to blame the person for being late. Spending an hour or more on the road is a waste of time. You could have spent it with your friends, family, or your study. The traffic situation in the country is very alarming and I think something must be done to improve it or at least minimize congestion.
REFERENCES:
https://wallpapersmug.com/download/1024x768/7e9732/night-landscape-highway-long-exposure.jpghttps://images.squarespace-cdn.com/content/v1/5991c9fb37c581e9a21d30ac/1564581041826-LU5WMXJ0TOJEUHGJGGU7/traffic-flow-optimization-solutions.jpghttps://i.pinimg.com/736x/c6/0e/8e/c60e8ecb2b87bd2cbc6bb48ac887fbed.jpghttps://www.civil.iitb.ac.in/tvm/nptel/512_FundRel/web/web56x.pnghttps://www.civil.iitb.ac.in/tvm/nptel/512_FundRel/web/web.htmlhttps://www.webpages.uidaho.edu/niatt_labmanual/chapters/trafficflowtheory/theoryandconcepts/QueuingTheory.htm#:~:text=Queuing%20Theory%20can%20be%20used,flow%20on%20one%20intersection%20approach.https://slideplayer.com/slide/14931352/91/images/14/The+queueing+theory+model.jpg
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