Traffic Systems Design
Traffic Systems Design CE 474
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Class 05 Traffic Systems Design CLASS PLAN AND RECORD ClassDate Class 06 8 September 2008 Plan Topics to Cover Record of Activities Problems Issues Success 8 September 2008 Class 05 Traffic Systems Design Slide Notes 1 Welcome to Class 05 Outline of topics to cover today Web site of the day 2 3 4 Quiz I give reading assignments ahead of time and I give you study questions so that you can focus on the important points that we will cover and discuss in the following class period These are not optional readings they are given with the expectation that you will read the material and that you will be ready to discuss it Today we will have a short quiz that covers some of what we discussed last week and some of the reading for today Please take out a blank sheet of paper and be ready to answer these questions individually H If you were designing this intersection with a goal of achieving LOS D would you be satisfied or not Why is the uniform delay term not adequate to represent the performance of this intersection N U Write the degree of saturation in a form that includes the green time Hint X vc 4 What is a ring l 5 What is a ring diagram What is phasing From the perspective of the HCM it is the part of the signal cycle allocated to any combination of traffic movements receiving the right of way simultaneously during one or more intervals see screen shot on slide Why is this different from the phase definitions we will use 0 In the HCM we assume a fixed set of intervals that always come in the same sequence that represent one cycle that is representative of the intersection that we are studying In reality green time that we observe is the result of a complex interaction of timing processes in the traffic controller and the users that are detected by the traffic control system 8 September 2008 2 Class 05 Traffic Systems Design Slide Notes 9 So what is a phase It is a controller timing unit associated with the control of one or more movements The slide shows the movements each numbered and the phase number same number associated with the movement Remember that a movement reflects the user perspective It is defined by the user type vehicle pedestrian for example and the action that is taken turn left for example A movement either has absolute right of way or relative right of way it can go but must yield to opposing movement A movement is an activity in response to a go indication Interval Duration of time where all displays remain unchanged Mode of signal operation Pretimed or actuated What is the definition of each 8 September 2008 Class 05 Traffic Systems Design Slide Notes 10 Now let s consider the concept of the ring diagram and rings and barriers as shown in this slide H N U 5 U1 Some UJNH 4 Phases are organized by grouping them into a continuous loop or ring and separating the crossing or conflicting traffic streams with some sort of time separation either a Making the movements sequential or b Adding a barrier between them The ring identifies the phases that must operate one after another Of course there is a change interval yellow and clearance time all red that separate the movements as well For example in ring 1 the phases that operate sequentially are phases 1 2 3 and 4 In ring 2 the sequential phases are 5 6 7 and 8 The barrier separates eastwest and northsouth conflicting movements The barrier represents a point in the cycle in which both rings must terminate a phase and begin a new phase Rings define the sequence of phases Rings separate conflicting LT and TH movements Barriers separate orthogonal pairs of movements rules Ring 1 includes phases 1 through 4 Ring 2 includes phases 5 through 8 Phases must end simultaneously at the barrier For example the pairs 12 and 34 must end simultaneously And the pairs 56 and 78 must also end simultaneously For lagging left turns the sequence would be 21 not 12 Common practice 1 2 2 6 are the main street through phases 4 is sometimes shown as north not strict 11 Now well give you the chance to test your understanding of the ringbarrier concept Work with a partner to construct ringbarrier diagrams for each of the following plans The solution will be posted on the class web site Estimate time 10 minutes 8 September 2008 Class 05 Traffic Systems Design Slide Notes Add text on precedence graphs and examples of critical path through the timing network 12 In lab tomorrow you will learn how to use a microsimulation model This slide which we ve seen before shows a classification of models A microsimulation model includes the following characteristics 0 We consider the behavior of individual behavior reacting either to drivers in front of them or the signal display status 0 Driver behavior is stochastic drivers behave differently and the same driver may behave differently at another time o The model keeps track of vehicles and processes at very small time steps here 01 second 0 The model can consider a large arterial or network of streets and intersections o The model can consider both fixed time and actuated traffic control systems 0 The model simulates a given set of conditions and does not usually find the optimal solution to your design problem 0 The model can consider both oversaturated congested conditions as well as undersaturated conditions This contrasts with the HCM 0 We consider macroscopic flow 0 Driver behavior is deterministic 0 Large time slices are used usually 15 minutes 0 Single intersections are modeled with little or no interaction between adjacent intersections o The model is based on fixed time traffic control though it provides an approximation of actuated traffic control systems 0 The model can both simulate and optimize o The model is better when conditions are undersaturated 8 September 2008 Class 05 Traffic Systems Design Slide Notes 13 You have to walk before you can run and the process of constructing a microsimulation model is not easy Students often react to the length of time that it takes to construct the model the ease of making mistakes and misunderstanding the rules that a given model imposes and the challenge in calibrating a model to the particular conditions that you will be studying Know this before you begin Simulation is a powerful tool but it is only a tool With that being said here is where you can go with a simulation model This is a model of downtown Moscow that students constructed in this class using the VISSIM model It is an quotaviquot file produced by the VISSIM model see handwritten notes 8 September 2008 CE474 Traffic Systems DesignFall 2004 J Class 01 Introduction to Traffic Systems Design August 23 2004 Ahmed AbdelRahim Civil Engineering Department University of Idaho CE475 Traffic Systems DesignFall 2004 Class Objectives Apply basic traffic flow theories at signalized and unsignalized intersections Q Use standard simulation and optimization models used by traffic engineering rofessionals to develop and evaluate control plans or signalized intersections a Complete a signal timing design for an isolated intersection and an urban arterial system Pre are and clearly and effectively present the fin ings of your design work Use hardwareintheloop simulation to test a signal timing design if Apply the factors that make for successful design teams CE475 Traffic Systems DesignFall 2004 a mngineer vs Civil Engineer CE475 Traffic Systems DesignFall 2004 Traffic Systems Design The Problem it 250000 traffic signals in US 60 of the oil that we use in transportation is imported 23 of all miles traveled each year on streets controlled by traffic signals 0 25 of fuel consumed waiting at traffic signals 50 of all transportation professionals will retire in 5 years a Some signalized intersections carry over 100000 vehday 1A of all agencies last retimed signals 4 years ago CE475 Traffic Systems DesignFall 2004 Traffic Systems design The challenges IOptimal DesignWhat s Optimal itif The timehorizon Availability of data Stochasticness of traffic CE475 Traffic Systems DesignFall 2004 WHY BUILD A TRAFFIC SIGNAL Traffic is congested Serve new land uses itSafety Levelof Service New road connections Traffic pattern changes CE475 Traffic Systems DesignFall 2004 BENEFITS OF SIGNALIZATION Reduce frequency of certain crash types especially rightangle a Create orderly traffic movement Increase traffichandling capacity CE475 Traffic Systems DesignFall 2004 3 Provide for con nuous flow 31 Function as part of signal system Allow vehicles peds and bikes to cross traffic stream CE475 Traffic Systems DesignFall 2004 DRAWBACKS Q Expensive 120000 for equipment Ongoing maintenance 4000 per year 3 Motorists still have to stop Increase of certain crash types rearend type i People may disregard 64 Excessive delay CE475 Traffic Systems DesignFall 2004 TRAFFIC SIGNAL STANDARDS 6 Signal design standards come largely from Manual on Uniform Traffic Control Devices MUTCD Institute of Transportation Engineers ITE f t 2 l MU tell i l l liml it i l W if T F39 9 if State Local standards example liln altitrn 5H r x V 21 391 r 6quot quot 3 quot ill 1 whim v it squot 4 5 2 if JquotQ L v ti CE475 Traffic Systems DesignFall 2004 CE474 Traffic Systems DesignFall 2004 J Class 3 Traffic flow models at intersections August 29 2004 Ahmed AbdelRahim Civil Engineering Department University of Idaho CE475 Traffic Systems DesignFall 2004 Design Project 1 Project Requirements Design report 1 is due at the beginning of class on September 14th ltrgtThe report must be no longer than 20 pages including all text figures and tables The report should clearly describe the design alternatives that you considered the range of values that you considered for each parameter the results of the analysis of the alternatives your final desicn pa39ameters and why you selected your nal ces on parameters itEThe report should also include all supporting information including figures tables and computations CE475 Traffic Systems DesignFall 2004 Project Requirements cont 6 a You will be responsible for developing the optimal signal timing for the intersection given a set of future projected traffic volumes You should clearly define what you mean by an quotoptima quot signal timing plan You may consider changes to lane configuration or alignment as long as your design remains within the existing curbtocurb right of way if The signal timing design will include the following parameters 1 phasing plan 2 cycle length 3 green splits 4 pedestrian phase lengths 5 yellow time 6 allred time CE475 Traffic Systems DesignFall 2004 Project Requirements cont You should define a set of phasing plans and a range of timing parameters that are appropriate to be considered as alternatives for your intersection You should conduct your analysis of the design alternatives using the Highway Capacity Software and the CORSIM simulation model Average control delay per vehicle volumecapacity ratio and queue length should be used as your measures of effectiveness in optimizing your design CE475 Traffic Systems DesignFall 2004 What happens if one or more design i parameters were not designed appropriately if L7 57 i i i 39 a i i CE475 Traffic Systems DesignFall 2004 Today s objectives Apply principal traffic flow theories at signalized intersections is Interrupted Flow Applications Signalized intersections Unsignalized intersections Stopango operation Traffic Flow Theories Arrivaldeparture Headway distribution Deterministicstochastic queuing theories Queue forming Polygons CE475 Traffic Systems DesignFall 2004 Microscopic Flow Characteristics Time Headway Definition iiistance gag Poin Time TloTloccupancy time for vehicle 1 h1 2t239t19 h23t339t29 h34T439T39 Etc CE475 Traffic Systems DesignFall 2004 Microscopic Flow Characteristics I 39ime Headway Distribution Headway Distribution NB Traf c 123456789 10 11 Headwayiseci 12 13 14 15 16 17 18 19 HHHHH av sec Headway Distribution Northbound Traf c Headway Distribution Eastbound Traf c CE475 Traffic Systems DesignFall 2004 Time Headway Distribution Studies a Capacity Gap acceptance at unsignalized intersection Permitted leftturn movements Safety Human factors and gap acceptance at What happens if a headway was misjudged CE475 Traffic Systems DesignFall 2004 Microscopic Flow Characteristics Time Headway Classification Random Headway State Negative ExponentialPoisson count Distribution Constant Headway State Normal Distribution Intermediate Headway State Pearson type II Gamma Enlarg Negative Exponential shifted Negative Exponential CE475 Traffic Systems DesignFall 2004 Microscopic Flow Characteristics Random Headway StatePoisson Distribution mxem x Px Probability that exactly X number of events occur time interval t m Average number of events time interval t e Napierian base of logarithms e271828 P06 CE475 Traffic Systems DesignFall 2004 Examples of using Poisson Distribution neantersection approach with a left turn volume of 120 vph Poisson what is the probability of skipping the green phase for the left turn traffic if you have an actuated signal and a 90 seconds cycle m Average number of left turn vehicles per Cycle number of cycles per hour 360090 40 x m m 6 m 120 vph 40 3 vehiclescycle Px T Probability of x 0 P0 0049787 49 196 cycleshours CE475 Traffic Systems DesignFall 2004 WW An intersection is controlled by a xed time signal having a cycle length of 55 seconds From the northbound there is a m turn movement of 175 vph If two vehicles can turn each cycle Without causing delay on What percent of the cycles will delay occur i m Average number of left turn vehicles per Cycle number of cycles per hour 360055 6546 m 175 vph 6546 267 LT vehiclescycle m Px mx6 Probability of X gt 2 x P xgt2 1 P0 P1 P 2 1 0069 0185 0247 499 3267 Cycleshour CE475 Traffic Systems DesignFall 2004 Qonstant Headway StateNormal Distribution Mean time headway h 3600V Normal distribution with mean u and standard deviation 8 95 con dence interval in the range it i 2s Minimum headway CL LL ZS or t ZS Then sh 0L2 CE475 Traffic Systems DesignFall 2004 Constant Headway StateNormal Distribution Normal Distribution To get the probability P As X lt B 2 B A From the table using the value ZS CE475 Traffic Systems DesignFall 2004 Constant Headway StateNormal Distribution 7 Example V 2000 Vph t 36002000 18 seconds Assuming a minimum headway of 06 seconds s 18 062 06 CE475 Traffic Systems DesignFall 2004 Constant Headway StateNormal Distribution m the probability P 10 S h lt t Z 18 10 08 ZS 08 06 1333 P 10 s h lt 18 0408 408 of the headway between the mean headway and 10 second CE475 Traffic Systems DesignFall 2004 Intermediate Headway State Generalized Mathematical Model Approach lt gt Composite Model Approach 5amp2 Other Approaches CE475 Traffic Systems DesignFall 2004 CE474 Traffic Systems DesignFall 2004 K Class 23 Highway classifications November 10 2004 Ahmed AbdelRahim Civil Engineering Department University of Idaho KW CE475 Traffic Systems DesignFall 2004 Exam 2 Review 6 Covers All materials covered in class and design oj ects 2 and 3 pr Isolated actuated operations Coordination concepts Manual calculations Trnasyt optimization concepts Actuated coordination calculations permissive periods ITS corridor management applications and their potential bene ts ITS architecture standards and protocols Diamond interchanges Roadway classi cation CE474 Traffic Systems DesignFall 2004 The Concept of Highway Function Classification Group street and highways according to the type of service they are intended to provide High way network roe Pro yde access to properties Pro IIde tra ve mobiity to users Probem con ict between serving through movements and pro IIding access to the dispersed pattern to trip origin and destnation CE474 Traffic Systems DesignFall 2004 The neighborhood network Hierarchical Road Network Grid Road Network CE474 Traffic Systems DesignFall 2004 Road Category groups rClassification Criteria Location inside urban or outside rural buildup areas Degree of concentration of access points on the road low or high Design function mobilityconnectors access collectors or local and pedestrian use CE474 Traffic Systems DesignFall 2004 Road Category Groups Group A Rural principal arterials freeways and interstates linkage between cities etc Group B Primary arterialsSuburban areas Group C arterials used as collectors in urban areas Group D urban roads that provide access to areas adjacent to the road Group E Local urban roads CE474 Traffic Systems DesignFall 2004 The Trend Context Sensitive Design CDS e Context sensitive design CSD is a collaborative interdisciplinary approach It involves all stakeholders to develop a transportation facility that fits its physical setting and preserves scenic aesthetic historic and environmental resources while maintaining safety and mobility How CSD is different that the normal design process or is it CE474 Traffic Systems DesignFall 2004 Road Classifications How about Speed limit fSpeed zoning is the establishment of safe and reasonable speed limits for certain special zones or sections of highway where the statutory speed limits do not fit the roadway and traffic conditions Discuss speed zoning methods used by five different states to set speed limits in rural and urban highways CE474 Traffic Systems DesignFall 2004 CE474 Traffic Systems DesignFall 2004 J Class 02 Introduction to Systems Engineering in traffic systems design August 25 2004 Ahmed AbdelRahim Civil Engineering Department University of Idaho KW CE475 Traffic Systems DesignFall 2004 Traffic Signal Systems What Things a 6 7 A re there Why they are there i 3 quot 9 i b 1 A AW 7 CE475 Traffic Systems DesignFall 2004 Traffic Systems Design Systems Engineering Approach 5 Systems engineering involves the transformation of an operational need into a description of system performance parameters and a preferred system configuration at This must be done through the use of an iterative process of functional analysis synthesis definition design testing and evaluation The systems engineering approach seeks to maximize efficiency and effectiveness through employing a continuous and iterative process that incorporates the feedback actions necessary to ensure convergence to the most optimal solution Systems engineering approach should be used in this course CE475 Traffic Systems DesignFall 2004 Traffic Systems Design Systems Engineering Approach There are several systems engineering models that can be used FHWA recommends the V model The V model is a threedimensional systems development model that includes decomposition verification and resolution processes CE475 Traffic Systems DesignFall 2004 Erigi e39e39ringmApproach 0 Traffic Systems Design Systems O 0 o 0 CONCEPT OF OPERATIONS DEVELOPM ENT I OPERATIONS AND MAINTENANCE AND gesting quot quotquot quot Ve fication quotquot 39 39 SUBSYSTEM VERIFICATION Elation Integration E Veri cation Decompositio and and Validation Definition Testing Time CE475 Traffic Systems DesignFall 2004 Traffic Systems Design Systems Engineering Approach Systems engineering in CE474 Design PrOJects Assessment of project requirements Document and assess the extent of available resources Review and documentation of design options Summary of design parameters Plan for conducting analysis Detailed design Evaluation and testing Compare with requirements CE475 Traffic Systems DesignFall 2004 Traffic Systems Design Design Project 1 at Design fixedtime control plans for the intersection using m volumes SH 8 and Farm Road St SH 8 and Warbonnet St 5 Requirement All approaches operate C or Better Traffic Impact Analysis Trip Generation CE475 Traffic Systems DesignFall 2004 Traffic Systems Design Design Project 1 Warbonnet St amp SH 8 CE475 Traffic Systems DesignFall 2004 Traffic Systems Design Design Project 1 Farm Road St amp SH 8 1 I CE475 Traffic Systems DesignFall 2004 Traffic Systems Design Design Project 1 Student Assignment 1 Kebab Mohammad Wassim Farm Road and SH8 2 Reed James Evan Farm Road and SH8 3 Arellano Lisa Jo Farm Road and SH8 4 Luo Min Farm Road and SH8 5 CandiaMartinez Mario Guillermo Farm Road and SH8 6 Pakalapati Srinivas Raju Farm Road and SH8 7 Wu Lei Farm Road and SH8 8 Aeneni Shravan Kumar Warbonnet and SH8 9 McLenna Patrick Michael Warbonnet and SH8 10 Gangula Sreenath Reddy Warbonnet and SH8 11 Baden Andrew Christopher Warbonnet and SH8 12 Orton Brent Lee Warbonnet and SH8 13 Auch Alisha Fern Warbonnet and SH8 14 Carter Steven Neil Warbonnet and SH8 CE475 Traffic Systems DesignFall 2004 Traffic Systems Design Design Project 1 Task 1 Existing Conditions Inventory Field visits Documentation koield data collection What to collect Who collects what group Data Collection Plan CE475 Traffic Systems DesignFall 2004 24 Using Real World Data to Describe Driver Behavior While the models that we considered in section 23 provide an excellent framework for understanding traffic flow at a signalized intersection they still lack an important ingredient that we observe in the real world The models are deterministic and the real world is stochastic In this section we consider a very fine grained data set that was collected in Los Angeles that will allow us to consider the messiness or stochasticity that is every present in the real world 241 NGSIM data set In 2006 the Federal Highway Administration published the results of a study of traffic flow characteristics along Lankershim Blvd in Los Angeles The study was based on very high quality video that was taken from a 30 story building located adjacent to Lankershim Blvd New video image processing software extracted data on position velocity and acceleration for vehicles traveling along the arterial for a 30 minute period at time intervals of 01 second This is by far the most detailed study of vehicle trajectories ever completed Figure 1 shows an aerial view of one of the four signalized intersections included in this study It is the intersection of Lankershim Blvd Campo de Cahuenga Way and Universal Hollywood Drive located near Universal Studios In this section you will complete six studies using this data set that will allow you to learn how the behavior of real world drivers compares with the models that we considered in section 23 Overview of NGSIM data set characteristics etc 1 chapter024 v04docx 15 June 2007 Chapter 2 Users Figure 1 2 chapter024 v04docx lSJune 2007 Chapter 2 Users 242 Exercises Exercise 1 Drivers responding to yellow and red indications The purpose of this exercise is to learn how to quantitatively describe the response ofa driver to the yellow and red indications You will use two data sets each describing the movements oftwo vehicles along Lankershim Blvd Each data set includes the location of the two vehicles at tenth of a second time increments as well as other information such as speed acceleration and vehicle size When you have completed this exercise compare your solution with the example answers given on page xx Task 1 Prepare trajectory plots distance vs time for both vehicles with time on the x axis and distance on the y axis Locate the intersection stop line on the trajectory plot showing where each of the two vehicles comes to a stop Identify when each of the drivers begins his stopping maneuver noting the distance that the vehicle travels and the elapsed time between the initiation of the stopping maneuver and when the vehicle comes to a complete stop What differences do you observe in the behavior of the two vehicles Task 2 Prepare plots of vehicle speed vs distance from the stop line and speed vs time until the vehicles come to a complete stop Based on these plots describe the stopping maneuvers of the two vehicles What differences do you observe in the behavior of the two vehicles Trajectory of a single vehicle responding to yellow display Explore data for one vehicle following a first in queue vehicle through the arrival at the intersection stopping for the red reacting to the green possibly traveling through two intersections The exploration would be plotting the trajectory noting speed profile or plotting speed profile noting when driver responded to yellow or red and then to green Include time space trajectory plot speed profile plot discussion of two reactions to YR and to G compare with idealized plot Identify second data set for stopping vehicle at intersection 3 and have them run tasks for both data sets In this way the student can see two examples of driver reaction to both yellow and red It may also be of interest to find two reactions to red or an already stopped queue 3 chapter024 v04docx 15 June 2007 Chapter 2 Users Objective learn how to quantitatively describe the response of a driver to the yellow indication Tasks 1 Use data set for vehicle 208 2 Plot the distance vs time for this data Describe what you observe in the plot Note that the yellow interval begins at xxx for intersection 3 5 Plot the vehicle speed vs time and vehicle speed vs distance Using both the plot and the original data as your source describe the stopping decision making and behavioral process that the drivers have followed What are the time intervals that you observe Do the differences between the two drivers relate to speed Or to the distance away from the intersection at the beginning of yellow 4 chapter024 v04docx 15 June 2007 Chapter 2 Users 2000 2000 1500 1500 t1 2 ul 0 1000 1000 5 E n 500 500 0 1100 1150 1200 1250 1300 1350 1400 0 500 1000 1500 2000 FramelD E0 60 E E 2 2 1 40 1 u u u u n n m m 20 0 0 500 1500 2000 1500 1000 0 FramelD Disuneeupsueamofmp bank 60 50 40 E E 2 2 f 1 30 u u u u R R 20 10 200 150 100 50 0 1230 1250 1270 1230 1310 1330 Distaneeupstreamofstop bank FramelD chapter024 v04docx 15 June 2007 Chapter 2 Users 2 Trajectory ofa single vehicle responding to the green display 3 Trajectories of a platoon of vehicles responding to yellow display Explore data for set of vehicles arriving at red and departing at green Plot trajectories for all vehicles and note how this compares to the ideal case headways are not uniform speeds are not constant arrival patterns 4 Trajectory ofa platoon of vehicles responding to the green display 5 Headway patterns at start of green including saturation headway Explore saturation headway data for several green intervals enough so that we see some statistical variation for a through and left turn lane Compute headway by position in queue and saturation headway Relate to driver response issue Relate to ideal case Why variability is important 6 Flow profile diagram accumulated vehicle curve and queue accumulation polygon using two data sets or time intervals Prepare flow profile accumulated vehicles QAP plots for a data set Compare with ideal case Discuss why variability is important Dennis Strong model test 7 Delay computation Delay calculations using a cumulative vehicle plot or QAP How delay measurements compares to HCM estimates 8 Problem of where to measure arrivals since the real world can t have vertical queue 6 chapter024 v04docx 15 June 2007 Chapter 2 Users 7 chapter024 v04docx 15 June 2007 Chapter 2 Users 242 Start of green The figures on the following pages show a sequence of eight vehicles arriving at and departing from the northbound approach of this intersection 8 chapter024 v04docx 15 June 2007 Chapterz Users Study the eight pictures on beiow and on the foiiowing page The pictures show eight h39 39 the39 39 the J the intersection in the ieftrmost through iane Beiow each picture isthe time frame in tenths ofa second thatthe vehicie enters the intersection For exampie vehicie 86 entersthe intersection at time frame 883 or 883 seconds after the beginning of the observation period 11 i i Vehicle 85 enters the intersection at time frame tion at time frame 883 39 39 39 u 39 e we nLLi nieiinei nLLi n at the beginning or green and 21 seconds after vehicle 85 39 39 39 39 Vehicle 1M 39 39 922 18 Seconds after Vehicle 87 955 33 Seconds after Vehicle 90 9 chapter024 v04docgtlt 115 June 2007 Chapterz Users The text associated with each picture aiso shows the headway between a given vehicie and the previous vehicie to enterthe intersection For exampie the headway between vehicie 144 and 154 is 14 seconds Vehicle 1 4 39 Vehicle quot 4 959 14 Seconds after Vehicle 144 990 21 Seconds after Vehicle 154 10 Chapter024 V04docgtlt 15 June 2007 Chapter 2 Users The figure below shows a plot of the eight vehicles as they approach and leave the intersection The first vehicle in the queue stops just upstream of the intersection stop line or at a position of 347 feet Just for reference the left side ofthe photograph is at a point 84 feet upstream ofthe stop bar or a position of 263 feet So what does this figure show and how is it different from the earlier time space diagram see page xx Four vehicles arrived during the red interval as shown by the four horizontal lines on the left portion of the diagram The next two vehicles arrive after the beginning of green but as shown by the change in the slope oftheir trajectories are somewhat delayed as the queue is still clearing The final two vehicles experience no delay their slopes do not change indicating that the vehicles travel at constant speed arriving at and traveling through the intersection 500 400 C 9 0 n 300 200 800 900 1000 1100 Time Figure 2 The following figure shows even more detail regarding these vehicles The chart below shows the headways between vehicles at ten foot increments beginning near the stop bar LocalY 350 and up to 100 feet upstream of the stop bar LocalY 250 The vehicle speeds shown in feet per second are shown in the circles again at ten foot increments One question that this raises when we talk about saturation flow rate and 11 chapter024 v04docx 15 June 2007 Chapter 2 Users saturation headways we have traditionally meant with respect to the stop line But when we take a broader view of saturation headway or flow rate we see that for the queue clearance period the headways are longer as the queue begins to move and then shorten as the queue picks up speed For example consider the headways between the third and fourth vehicles 90 and 144 as the queue begins the headway is 52 seconds at fifty feet upstream of the stop line The headway decreases to 33 seconds when the vehicles pass by the stop line at LocalY 350 This finding may have an implication for traffic signal settings passage time and minimum green time when the detection zone is located upstream of the stop bar We can also follow the speed variation as the vehicles as the queue begins to move at the beginning of green The second vehicle in the queue vehicle 87 is traveling at 4 feet per second at a position of 330 feet just after it begins to move 15 feet per second at a position of 340 feet and 20 feet per second just after passing the stop line Vehicle 87 reaches its desired speed of 61 feet per second nearly 300 feet downstream of the stop line 350 E 340 330 E Veh 320 86 87 310 90 300 144 i 154 290 192 194 280 g 208 7 33 24 45 47 35 44 260 f 46 f 48 55 35 49 250 39 39 39 I 39 39 39 39 39 39 39 39 39 39 39 800 850 900 950 1000 1050 1100 G Vehicle speed 919 Headway Figure3 12 chapter024 v04docx 15 June 2007 Chapter 2 Users Headway as a function of distance upstream ofthe stop bar This is start of green behavior 4 Headway sec UJ 100 200 Local Y feet 86 87 87 90 90 l44 144 154 154192 192 194 194 208 300 400 Figure 4 chapter024 v04docx 15 June 2007 Chapter 2 Users Discussion of saturation headway where it is measured and how we can see it graphically in the figure 350 340 330 320 310 300 290 280 270 260 250 800 850 1000 1050 1100 Vandapan c u gt Filmy 243 End ofgreen behavior 14 chapler024 v04d0cx15une 2007 Chapter 2 Users Position Time Speed ftsec B 8 K 86 J 87 Z 90 10 O I I I I I I I I I I I I I I I I I o 100 200 Local Y feet 15 chapter024 v04docx 15 June 2007 Chapter 2 Users 3O 20 I l 00 400 Acceleration ftsec2 O I Local Y feet 16 chapter024 v04docx 15 June 2007 Chapter 2 Users 244 Flow rate models Instanteous flow rate vehhr 3000 2500 2000 1500 1000 500 1000 Time frame ID 1050 1100 Figure 5 Flow profile chapter024 v04docx 15 June 2007 Chapter 2 Users Arrivals Vehicle number Departures 200 400 600 800 1000 1200 Time FramelD oArrivas Vehicle number Departures Depanurenme hasbeen modified by 20 seconds to account fo ravel from 250 to 350 200 400 600 800 1000 1200 Time FramelD 18 chapter024 v04docx 15 June 2007 Chapter 2 Users Vehicle number Depa uretime has been modified by 20 secondstoaccount fortravel trom 250 to 350 200 300 400 500 600 700 Time FramelD 800 900 1000 1100 chapter024 v04docx 15 June 2007 Chapter 2 Users Exercise Add assignment using data for the first cycle for lane 1 You are given field data for one lane ofa signalized intersection The data give the location of eight vehicles over a period of three minutes at one foot resolution and the time that each vehicle passes each one foot point Using the field data tab on the spreadsheet prepare a time distance plot for the eight vehicles placing distance on the y axis and time on the x axis Note that the location of the stop bar for our subject intersection is at a distance of Y 346 feet Change the chart settings to show the range y 200 feet to 400 feet and x 20 seconds to 120 seconds Answer the following questions o Is there movement in the queue while the vehicles are supposedly stopped 0 Which vehicles are directly affected by the red display 0 Which vehicles are affected only by the behavior of their leading vehicles 0 Which vehicles are not affected by either the red display or their leading vehicles How far upstream does the queue extend Using this point as the system entry point to your queuing system prepare a cumulative vehicle plot showing the arrival time into the system and the departure time from the system Using this plot show the time that each vehicle is in the system delay time Compute average delay per vehicle Using the uniform delay term only compute the average delay per vehicle for this approach Consider the two estimates of delay which one is more valid How might you explain the difference or similarity in these two estimates see spreadsheet file exercise dataxlsx for details 20 chapter024 v04docx 15 June 2007 Chapter 2 Users 1500 1000 VehD 1 a 39 VehD 2 EI VehD 3 E E VehD 4 a VehD 5 500 VehD 6 VehD 7 VehD 8 O I o 200 400 w I 350 VehD 1 a 39 VehD 2 a 39 E 300 Veth 3 E VehD4 3 VehD 5 39 VehD 6 250 VehD 7 I VehD 8 200 39 39 39 39 39 20 70 120 Time sec 21 chapter024 v04docx 15 June 2007 Chapter 2 Users m 2 U E W gt u o a Arrivals D g IDepartures Z I I I I 39 I 20 4O 60 80 100 120 Time 22 chapter024 v04docx 15 June 2007 Chapter 2 Users 245 Single lane vs multi lane headway distribution The following chart shows the three lanes for the Northbound approach showing the headways computed for each lane three channels and when computed together one channel This discussion is important for the next section on detectors 10 o 8 El 0 6 3 gt2 N 3 quotg 0 Three channels cu o I I 4 EIOnechannel O 9 2 A I I o 393 39 39 u D 0 El 0 u D a El 339 llzl DD 539 0 800 850 900 950 1000 1050 1100 1150 1200 FramelD 23 chapter024 v04docx 15 June 2007 CE474 Traffic Systems DesignFall 2004 KJ Class 16 Actuated Coordinated Operations October 18 2004 Ahmed AbdelRahim Civil Engineering Department University of Idaho KW CE475 Traffic Systems DesignFall 2004 Coordination of Actuated System Definitions Cycle Length The Cycle Length is an amount of time in seconds that is required to go from the beginning of the Main St green interval serve all of the Main St green yellow and red intervals serve all of the other phases green yellow and red intervals at the intersection and return to the beginning of the Main St green interval CE474 Traffic Systems DesignFall 2004 Coordination Definitions SQIit A Splitis the amount of time allocated to a given phase to run the Max Green Yellow and Red Intervals CE474 Traffic Systems DesignFall 2004 Coordination Definitions Offset An O setis a value in seconds that represents the difference between a reference point system zero and the beginning of the Main St green interval cycle zero at a specific intersection CE474 Traffic Systems DesignFall 2004 Coordination Definitions Force Off A Force Off terminates a specific phase or phases at a specific time within the cycle length This allows subsequent phases to be serviced at the proper time in the cycle CE474 Traffic Systems DesignFall 2004 Coordination Definitions Permissive Period Vehicle A Permissive Perquot00 is an amount of time in seconds with in the cycle length during which secondary or non coordinated phases are allowed to be serviced from the coordinated phases The Permissive Period has a beginning and ending period that defines when the phase is given the window of opportunity to be serviced CE474 Traffic Systems DesignFall 2004 Coordinated Signal Control iFor the critical intersection in your corridor Use Maximum Green Time parameters when choosing phase splits Include all signal clearance intervals 0 Yellow allred pedestrian clearance etc Add all green and clearance times to determine the cycle length Excess time from noncoordinated phases will revert back to the coordinated phase CE474 Traffic Systems DesignFall 2004 Force Off Permissive Worksheet Exercise 120 Sec Cycle Beginning of Qcle Qcle Length 0 1 20 Secont 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 Coordinate Phases Permissive 2 6 Coordinated Phases Permilive Period Cycle Length I The Coordinated Phases are always ALLOWED to be given a Green Indication I Pha Ri Pha Ri Green Time 5 Phase for Coordinated All Permissiv Permi e Phase 3 7 Force off F ermi Phases Coord Phase WR Walk Ped Clr 39 Phase 3 7 Min Gm CE474 Traffic Systems DesignFall 2004 Class 01 Traffic Systems Design CLASS PLAN AND RECORD ClassDate Class 01 25 August 2008 Plan Topics to Cover Record of Activities Problems Issues Success 25 August 2008 Class 01 Traffic Systems Design Slide Notes 1 Welcome to CE 474 I hope that you had a good summer Signup sheet with email addresses 2 Today s outline see list 3 Web site of the day Why do show these each time Today s site 0 US DOT 0 Two sites with history of traffic signal 4 Why traffic signal systems William Potts 1920 First three color four direction traffic signal in 1920 5 Garrett Morgan invention Electric automatic traffic signal 6 Congestion has been around as long as we have gathered in cities Here is Cleveland Ohio in 1915 7 Why do we consider traffic signals important as we talk about congestion see list 0 8 Why traffic signals ask them Two answers 0 To keep cars from running into each other 0 To make sure cars don t stop or don t stop for too long 9 But we are not doing a good job nationally in managing our signal systems and the congestion that results 10 So what is a traffic signal system Let s first look at the system components and how they interact 0 Users respond to display 0 Detection system responds to user 0 Controller responds to detector 0 Display responds to controller 25 August 2008 Class 01 Traffic Systems Design Slide Notes 11 Let s look at each of these interactions separately What do we see in this slide ask them there are many rich details starting with seven cars in queue an eighth about to join the queue and the eighth vehicle not making it through the intersection 0 Time space diagram 0 Vehicle trajectories o The vehicles respond to what is displayed 12 Let s say that there are loop detectors that are located at the stop bar Again we note the timespace trajectories of vehicles moving through the intersection and now passing through the detection zone When a vehicle is present the detection zone is occupied 13 When the detection zone is occupied a call to the controller is active and the controller responds The controller has a variety of timing processes that respond to these vehicle calls We see here two of the timing processes For example the minimum green timer begins at the beginning of the green indication and times down here reaching zero or expiring at 10 seconds after the beginning of green This also shows the passage time which we will learn about later that helps to determine when the green should end 14 Finally as a result of the timing processes in the traffic controller the various signal indications are displayed For vehicles these are green yellow and red 15 Here we see the system as it works together with each of these component relationships We will learn about each of these four components individually as you prepare your designs this semester 25 August 2008 3 Class 01 Traffic Systems Design Slide Notes 16 Now let s look briefly as what you will be doing during the semester You will be responsible for developing a signal design and timing plan for a system of three intersections in Moscow Here is an example 0 Twointersection system signalized 0 New entrance to the university and new development with major increases in traffic flows Your tasks 0 Develop phasing and timing plans including a coordination plan 0 Assess impact of new traffic generated by a new development Develop signal design and intersection design for an intersection that is currently not signalized O 17 Don t panic We will go through a series of exercises and labs that are designed to build the skills that you will need to accomplish the tasks listed on the previous slide I ve characterized these as the learning objectives that I ve set for you for this semester Note relationship to ABET objectives 18 Class scope and requirements This takes us to the class scope and requirements Everything is on the web site Everything will be done electronically 18 Web site information 25 Class scope and requirements Resources Schedule 26 Introductions As I may have mentioned we will be working in teams Tomorrow in our first lab we will form the teams I will make the team assignments But as a first stage of getting to know each other I want you to take five minutes to get to know someone what you haven t met before see list introductions MK introduction 25 August 2008 Class 01 Traffic Systems Design Slide Notes 27 Preparation for Tuesday s lab 0 Reading 0 Study questions It will be very common for us to have an assignment the day before often readings or problems with study questions that will help to focus your work You will be responsible for answering or discussing these study questions at the next class session These study questions will help to facilitate your preparation for each class Please take them seriously 28 Reflections and questions 0 Take three minutes and think about what we discussed today 0 Write one questions that you have on this material or the course or what we talked about today and send it to me via email mkyteuidahoedu We will periodically take time at the very end of class for you to consider the material that we have covered and to reflect on what you don t understand this is a powerful way of making sure that you get answered what you didn t quite get during class 25 August 2008 CE474 Traffic Systems DesignFall 2004 J Class 22 Traffic Signal System and ITS Architecture November 8 2004 Zhen Li National Institute for Advanced Transportation Technology NIA IT University of Idaho Ahmed AbdelRahim Civil Engineering Department University of Idaho r J CE475 Traffic Systems DesignFall 2004 Topic outline Interchange Introduction Diamond Interchange Introduction Diamond Interchange Signal Control Introduction Twophase control TI39 I Three phase control TI39I Fourphase control CE474 Traffic Systems Design Fall 2004 Definitions 6 Freeway a multilane median divided limitedaccess roadway In other words a multilane road with some form of barrier down the middle to separate traffic with ramps to get on and off Ramp a roadway which connects a freeway to a regular road a regular road to a freeway or a freeway to a freeway CE474 Traffic Systems Design Fall 2004 Definitions Interchange The connection of a freeway to a road or another freeway by a series of ramps The other road or freeway being connected to is gradeseparated Directional ramp A ramp which turns directional to where it39s going When the term quotdirectionalquot is applied to ramps it is usually referring to left exits on freeways CE474 Traffic Systems DesignFall 2004 Definitions 6 Flyover A semidirectional or directional ramp that is elevated above ground level This ramp flies over the freeway and other ramps Cloverleaf Refers to Cloverleaf style interchange or a single loop ramp CE474 Traffic Systems DesignFall 2004 An Interchange CE474 Traffic Systems DesignFall 2004 Interchanges Introduction Thru traffic on the t rough without Surface 139 s opping Even if traffic we 5 gnals are installed at 39139 the ends of the ramps Fl39E39El39fEI39J iquot traffic on the surface street blue also flows smoother without interference from the freeway 391 Exit Ramp Entrance Ramp CE474 Traffic Systems DesignFall 2004 The Full Cloverleaf Interchanges 6 The classic Cloverleaf allows quotnonstopquot full access between two busy roads Traf c merges and weaves but does not cross atgrade A W Full Cloverleaf CE474 Traffic Systems DesignFall 2004 Sixramp partial cloverleaf interchanges f The sixramp partial Cloverleaf A allows traffic on the side stree39 Q to flow more smoothly than a fgfggjggfrm plain diamond 0 Each side of the street has an E easy right turn to either W direction on the freeway 39v39ariant favoring traffic to Efrem the left CE474 Traffic Systems DesignFall 2004 Trumpets and other 3way interchanges 7 This is a conceptually simple way to end one freeway at another m V Trumpet CE474 Traffic Systems DesignFall 2004 SemiDirectional 4way or the Stack Interchanges 6 For two intersecting freeways Each road has a direct connection to the other roadways with no looping or weaving and the ramps cross in a 4 eve deck you can see for about a mile Ifthe ramps are two lanes wide the interchange has quite high capacity Four lave stack CE474 Traffic Systems DesignFall 2004 The Volleyball Interchanges This interchange is better known as the 3 eve diamond or split level diamond All turning motions are handled in an intermediate square structure connecting the eight ramps Turning traf c travels around the square in the same direction as a roundabout Through traf c can proceed on either intersecting road Without stopping Voliegbaii interchange CE474 Traffic Systems DesignFall 2004 Diamond Interchange 6 There are two intersections in the interchange There are four ramps In city environments the four ramps may come together close enough to form one intersection That39s called a Single Point Urban Interchange SPUI A Diam ncl CE474 Traffic Systems Design Diamond Interchange Cross street Exit ramp ix Entrance ramp V Major highway V Ramp terminal Cross street VA Frontage road j V EntranceM K K Qramp Major highway gt gt gt gt VnkK Ramp terminal CE474 Traffic Systems DesignFall 2004 Di 6 amond Interchange Characteristics 39 The basic diamond type interchange is composed of four oneway diagonal ramps often aligned in a relatively narrow rightof way These two intersections can be either above the highway or below depending on elevation of the site CE474 Traffic Systems DesignFall 2004 Diamond Interchange Characteristics f The diamond interchange is the simplest and perhaps most common type of service interchange 0 Reasons of the use of diamond interchanges in urban areas The simplicity of design minimum rightof way requirements Cost economy CE474 Traffic Systems DesignFall 2004 Diamond Interchange Design Factors 6 Exit ramp design should allow motorists to comfortably decrease their speed in order to egress from the freeway 0 Exit ramp location and length should also be sufficient to store vehicle queues without causing spillback conditions onto the freeway CE474 Traffic Systems Design Fall 2004 Diamond Interchange Design Factors 6 0 Entrance ramp length should allow motorists a sufficient distance for increasing speed to match those on the freeway 0 Entrance ramp design must also consider queue spillback as a result of ramp metering CE474 Traffic Systems DesignFall 2004 Diamond Interchange Design Factors Wnection between the ramp and the cross street is critical and adequate turning radii must consider usage by heavy trucks and other turning traffic Vertical alignment Sight distance Grades should not inhibit vehicle performance Ramp design and intersection spacing CE474 Traffic Systems Design Fall 2004 Diamond Interchange Eongestion Problems 39 Interchange signal queues blocking merge areas of exit ramps and the frontage road Interchange signal queues backing onto the freeway main lanes Exit ramp Ramp metering queues backing into the crossstreet intersection CE474 Traffic Systems DesignFall 2004 Diamond Interchange Phasing Sketc Phase 4 Frontage Road 6 Phase 1 lt m Interior LT quotquot39 Phase 6 Artenal i T PhasezArtenal th5 J Interior LT Y C W W Phase 8 Frontage Road CE474 Traffic Systems DesignFall 2004 Diamond Interchange Phase Design 0 The primary operational difference between diamond interchanges and standard intersections is that the paths of the opposing left turns interlock so that they can not be served simultaneously The phases that would normally con ict at a standard intersection are compatible at an interchange CE474 Traffic Systems DesignFall 2004 Diamond Interchange Phase Design 39 An overlap is de ned as a combination of movements that a single phase can run concurrently Diamond interchange movements 18 analysis Cross Street Movements spin gun n 7H CE474 Traffic Systems DesignFall 2004 Diamond Interchange Phase Design Frontage Road M oooo ent A le 4 QL lam f WWIquot J th J an 16 WEFTWF CE474 Traffic Systems DesignFall 2004 Twophase Control n The most basic type of diamond interchange phasing is twophase control quot Twophase control treats the intersections at the diamond as two intersections each having two basic phases The phases are the arterial or crossstreet phase and the ramp or frontage road phase CE474 Traffic Systems DesignFall 2004 Twophase Control n In two phase control the lefttum phases 11 and 15 are not provided separate phases and are operated as permitted left turns quot This type of control is used only for diamond interchanges operating under low volumes and Where sight distance allows a permitted movement CE474 Traffic Systems DesignFall 2004 Twophase Control 6 39 Twophase control reduces delay because there are fewer phases and correspondingly lower lost time and cycle lengths Twophase control is bene cial when the lefttum and or opposing through traf c volumes are light and lefttum movements are free to proceed during a longer duration than what otherwise would be provided CE474 Traffic Systems DesignFall 2004 Fixedtime Threephase Control 6 39 Traditional threephase control treats the diamon interchange as two intersections 39 Each intersection having three basic movements to service There are four different phase orders Lead Lead LeadLag LagLead LagLag CE474 Traffic Systems DesignFall 2004 Fixedtime Threephase Control 4 LEADLEAD m m E m w a LEADLAG gt gt gt 1 2 4 6 5 8 LAGLEAD 2 1 4 5 6 8 LAGLAG quot f gt gt 2 1 4 6 5 8 CE474 Traffic Systems DesignFall 2004 Fixedtime Threephase Control n The three phases at one of the intersections can be arranged two different ways Interior left turns can either lead or lag the arterial street movements The decision to lead or lag the leftturn movements depends largely on the intensity of the turning movements at the interchange and which approach is more critical CE474 Traffic Systems DesignFall 2004 Actuated Threephase Phase Control n The structures of threephase actuated strategies are created through the use of barriers 0 There are three levels of exibility that can be implemented basic extended exible threephase strategies CE474 Traffic Systems DesignFall 2004 CE474 Name Traf c Systems Design Fall 2004 page 15 Examination 1 1 Ifthe ideal headway for the northbound traf c on an intersection was found to be 189 seconds what is the capacity of the 3lane NB approach Cycle length 90 seconds with 35 seconds green for the NB approach 2For the NB traf c described in problem 1 if the average hourly volume is 1800 vph draw a queue forming polygon for one cycle Estimate the maximum number of vehicles in the queue and the amount of unused green during each green phase Assume a startup lost time of 3 seconds CE474 Name Traf c Systems Design Fall 2004 page 25 Examination 1 3On an intersection approach with a left turn volume of 300 vph Poisson The length of the left turn bay for this approach is 100 ft What is the probability of a spill back at that approach Left turn vehicles blocking the through lane The intersection is controlled by a xedtime signal with a 60 seconds cycle Assume an average vehicle length of 20 ft 4A1rivals at an intersection approach can be represented by a normal distribution with an average headway of 26 seconds What is probability of having headway greater than or equal 3 seconds Use minimum headway of 12 seconds CE474 Name Traf c Systems Design Fall 2004 page 35 Examination 1 SVehicles arrive at an automated highway toll facility with a rate of 360 vph Poisson It takes on average 6 seconds Negative Exponential to pay the toll and proceed through the toll facility What is the average waiting time at the toll facility What is the total delay resulting CE474 Traf c Systems Design Fall 2004 Examination 1 Name page 45 6The characteristics of a threephased signalized intersection is listed in the following table Traf c Volume vph Number Lane Saturation Left Turn Through Right Turn of Lanes Width Flow NB 13 0 600 70 2 12 1940 SB 200 450 100 2 12 1940 EB 90 300 50 1 12 1780 WB 1 10 2 10 90 1 12 1780 The phasing sequence for the signal is as follow Phase A Northbound traf c Through Left and Right moves SB EB and WB stop Phase B Southbound Traffic Through Left and Right moves NB EB and WB stop Phase C Eastbound and Westbound traf c Through Left and Right move NB and SB stop Assuming a startup loss time of 35 seconds per phase and an Amber time of 4 seconds for all phases using a cycle length of 90 seconds determine 1 The green time allocated for each phase 2 The volumecapacity vc ratio for all approaches 3 The average delay and LOS for each movement CE474 Name Traf c Systems Design Fall 2004 page 55 Examination 1 CE474 Traffic Systems DesignFall 2004 KJ Class 21 Traffic Signal System and ITS Architecture November 3 2004 Ahmed AbdelRahim Civil Engineering Department University of Idaho KW CE475 Traffic Systems DesignFall 2004 Ad vanced Traffic Management Systems in Idaho Traffic Signals Systems Integration and DeploymentCity of Moscow Idaho I l I 111 I t 5 39 A39c ii 1 n 1 a e we Single Intersection Enhance u e IA LJJ J39E U U National Transportation Communication for ITS Protocol NTCIP CE474 Traffic Systems DesignFall 2004 he city of Moscow Signal network CE474 Traffic Systems DesignFall 2004