 I welcome you all for this today's session on Fundamentals of Traffic Flow. Myself, Parshav Kumar, Assistant Professor, Department of Civil Engineering, Wall-Chain University Technology, Solapur. Learning outcomes of the today's class, at the end of the session students will able to distinguish between uninterrupted and interrupted traffic flow and also describe the characteristics of uninterrupted and interrupted traffic flow. We know that the traffic stream involves the driver vehicle and the physical road futures and its environment. In the driving, in the traffic stream involves the variability because the driver behavior varies, even speed varies and vehicle characteristics varies. So driver behavior depending upon the location and time and he is behavior in the traffic stream varies and some of the drivers will go with very high speed, some of the driver will go with very low speed. So speed also varies and vehicle characteristics, we have to consider like their length, then weight, then height, all the parameters are varies. So it is a very tough challenge for a traffic engineer to consider all these varying factors and design the facilities. In describing traffic streams in quantitative terms, a key parameters must be defined and measured. So key parameters in the traffic streams are flow, speed, density and capacity. So these must be described as well as measured. Now to understand this inherent variability and define normal range of behavior. So what is meaning of this normal range of behavior? Suppose if I take the example of speed as the example to define the normal range of behavior, some of the driver will go with very high speed, some of the driver will go with very low speed and which one we have to consider for defining this stream traffic stream parameters. Whether we should define all this considering the flow, it is uneconomical. So low, it is inadequate. Now we have to define all these traffic stream parameters for normal range of behavior. Say all the vehicles are traveling with the average speed in the traffic stream. For that average speed, we are defining all these traffic stream parameters and designing the facilities. Usually the traffic flow facility is classified in two ways, uninterrupted flow facilities and interrupted flow facilities. Let us understand these two parameters in detail. Uninterrupted flow facilities where there is no external factors to cause periodic interruptions to the traffic stream. What could be the external factors? External factors are traffic signals, stop or yield signs. Sometimes even in a long rural highways between signalized intersections, yes we can also go with uninterrupted flow. Primarily it exists on freeways. It means for a driver, there is no absolutely any external interruptions due to all these parameters. But it does not mean that driver can go with very high speed. Sometimes during a high volume also within the traffic stream, the flow might decrease because of the higher volume. So when the flow is decreased, even capacity decreases, speed decreases. But this external factors not because of the external factors, your speed is reduced. It is reduced mainly because of your interruptions due to the within the traffic stream. Because of the high traffic stream, your traffic speed is reduced or flow is reduced. Interrupted flow is opposite to that your uninterrupted flow. It means you are going to receive this external interruptions like signals, stop or yield signs at the intersections and it is not available for continuous movement and time enters as a significant parameter in affecting the flow. Because here you are trying to stop the vehicle and start the vehicle, stop and start. So in this one, the time enters as a significant parameter affecting the flow. So this happens unsignalized at grid intersections where we do not have any unsignal intersection. You need to wait for the opportunity and cross the intersection. Absolutely there is no control on that particular intersection. Curve parking, yes, where we have the curb parking, parking vehicles are parked on the road, parking, unparking. There you need to again stop the vehicle. So all these operations will have an interruption to the movement of the traffic. So this creates the platons of vehicles progressing in the traffic stream. So what is the platons of vehicles? A bunch of vehicles moving in the traffic stream is called the platons of vehicles. For example, if you are stopping the vehicle at intersection waiting for a green, so there once the green is given, all the bunch of vehicles are moving and next bunch of vehicles are moving at a distance of what? So one platons of vehicle to another platons of vehicles, the spacing is larger. Once the spacing is larger, we know that again the flow is going to be decreases. With this background of uninterrupted flow, let us define the traffic stream parameters. It is classified in two ways, macroscopic measures and microscopic measures. So macroscopic measures defines the volume, speed, density or concentration. So this describes a single value of each which applies to the traffic stream as a whole. So why we are calling as a single as whole? We are defining single volume, single speed, single density or concentration. So in the headway, this microscopic measure which measures the steam parameter within the traffic stream. It means from one vehicle to another vehicle, we are trying to measure the behavior of the vehicle within the traffic stream. So we call as we have time headway and space headway, we are trying to measure this microscopic measure within the traffic stream. Now let us define this traffic stream parameters one by one. So first one is the volume. Volume is defined as number of vehicles passing a point on highway or a given lane or a direction of highway during the specified time interval. So number of vehicles passing on a specified lane or a given direction in a per unit time. So here if you are standing on this particular location, you can observe the number of vehicles passing this particular lane, particular section per unit time. The per unit time might be 15 minutes or per hour, per day also. So it is expressed in per minute vehicles per day, vehicles per hour. So q equal to n by t, n is number of vehicles and t is the observation period. What is the rate of flow? Rate of flow generally expressed in units of vehicles per hour. But this represents the flow that exists for a period of time less than 1 hour. It means if you are measuring 200 vehicles in a 15 minute period, what is the rate of flow per hour? It is 200 into 4. This is 800 vehicles per hour. It means a 4, 15 minutes exist in hour. So 4 into 200 gives the 800 vehicles per hour. So that means 800 vehicles would not be observed if 1 hour was counted. So it is expressed per hour but this can be a 15 minutes or converted into a per hour traffic. The traffic flow measured in daily volumes and hourly volumes. Daily volumes are expressed in different ways. This daily volumes should consider the variations within a year, within a month, within a week and within a day also. So how we are trying to measure that? First parameter is ADT, average annual daily traffic. This considers the overall vehicle passing in a year divided by 365. So this ADT, average annual daily traffic, considers the variations in the three seasons. Suppose the variations in the rainy season is lesser and in summer season the traffic is higher. So this considers the variation throughout the year. If you want to find out the variation in the weekdays of an year, suppose if I consider the weekdays in a year considering the 5 weekdays for 52 weeks. So 5 multiplied by 52 gives 260 weekdays in a year. So you want to find out the weekdays traffic, variations in the weekdays traffic throughout the year. So we take the parameters average annual weekday traffic that is AWT. And another one ADT that is variations within a month. So you have the month traffic divided by the total month in a total days in a month that gives you ADT. Sometimes the 7 days traffic also we take the for calculation the ADT. Then AWT within a week within a month also you can calculate the AWT average 24 hour weekly volume at a given location over a defined time period less than one year. So all these parameters are defined in terms of vehicles per day. This is the example gives you how to measure the AWT and ADT. So first, second, third column the traffic is given number of weekdays in a month and number of days in a month and total monthly traffic for that particular month and total weekday traffic for the particular month. So we know that AWT average weekday traffic, average weekday traffic it is given by 5 by 2. So what is the weekday volume and number of the weekdays? So 5 by 2 gives the average weekday traffic and average daily traffic it is 4 by 3 that is monthly total monthly traffic and total month total days in a month so that gives you ADT. So now adding all together ADT average annual daily traffic so total all month traffic divided by the number of the days in the year gives you ADT and AWT all the weekday traffic in the year divided by the number of the weekdays in the year that gives you AAWT. Now pass for a while and try to give the correct answer for this question. Now pure uninterrupted flow exists on in where? State highways, MDR, national highways are freeways and ADT measures what? ADT measures seasonal variation within a year month or a week or a day. So I hope you are able to select the correct answer. The correct answer is the pure uninterrupted flow exists in a freeways and ADT measures the seasonal variation in the within a year. So what are the application of the ADT which we are average annual it is used for payment analysis for designing the thickness of the payment, calculation the crash data, estimation of the economic feasibility basis and finding out the highway user revenues and development of improvement and maintenance programs. So all where we are trying to use the ADT as the application parameter. These are the references I have prepared for used for preparing this presentation. Thank you.