IMSA Traffic Signal Technician I Study Guide PDF

STUDY GUIDE  6/26/2024 IMSA Traffic Signal...

STUDY GUIDE  6/26/2024 IMSA Traffic Signal Technician I Copyright © International Municipal Signal Association Revision Date: February 1, 2024 1 Traffic Signal Course Introduction Introduction to Traffic Signals Brief History Manuals and Agencies Lesson 1: Liability / Legal Responsibility Lesson 2: Personal Protection Equipment / Work zone safety Lesson 3: Signal Technician Tools Lesson 4: Electrical Theory Lesson 5: Traffic Signal Operational Concepts Lesson 6: Controller Assembly - Cabinet Components Lesson 7: Traffic Signal Construction Lesson 8: Signal Head / Installation Methods Lesson 9: Luminaires / Lighting Lesson 10: Vehicle Detection Lesson 11: Pedestrian Detection and Service Lesson 12: School Zone Flashers Lesson 13: Maintenance Section 14: Glossary 2 IMSA Traffic Signal Technician I Brief History 3 1  6/26/2024 Brief history of Traffic Signals A brief history of Traffic signals. The first recorded attempt at regulating traffic flow with a mechanical signal occurred in 1868 in London, England. A gas-lit semaphore 1868 jp knight 1868 first attempt tower, designed by railway engineer J.P. Knight, stood at the intersection of Bridge Street and Great George Street. It featured rotating arms with symbols indicating "stop" and "go," providing a rudimentary system of traffic control. One of the pivotal milestones came in 1912 Lester Wire 1912 First Electric signal when Lester Wire, a Salt Lake City policeman, developed the first electric traffic signal. This novel device employed red and green lights and a buzzer to guide the flow of vehicles, bringing a semblance of order to the bustling streets. 4 Brief history of Traffic Signals - Garrett Augustus Morgan Garrett Morgan was an African American inventor, businessman, and community leader who made significant contributions to various fields. One morgan 1923 added warning position of his most notable inventions was a three-position traffic signal, which greatly improved roadway safety in the early 20th century. Before Morgan's invention, traffic signals had just two positions: Stop and Go. These simple signals often led to confusion as they didn't provide any buffer between the stopping and going commands, resulting in frequent collisions between vehicles. Morgan's traffic signal, patented in 1923, added a "warning" position between the Stop and Go signals. This "all directions stop" stage allowed time for vehicles to clear the intersection before others began moving, reducing the risk of crashes. This concept is still used in modern traffic light systems, with the "warning" position now being the yellow or amber light we see today. In addition to the traffic signal, Morgan is also well known for inventing a type of gas mask that was used to protect firefighters and save countless lives. Despite the widespread use of his inventions, Morgan faced significant racial discrimination during his lifetime, a time when Black inventors rarely received credit or financial reward for their contributions. Despite these challenges, he continued to innovate and serve his community until his death in 1963. 5 Three Position Traffic Signal 6 2  6/26/2024 Brief history of Traffic Signals A brief history of the Traffic signals. In 1920, a significant breakthrough occurred with the invention of the three- potts 1920 3 color signal color signal system by William Potts, a Detroit police officer, who was later coined “Mr. Traffic light.” Potts introduced the concept of the amber, or yellow, light, creating a distinct phase that signaled caution, prompting drivers to prepare to stop. The addition of the yellow light added a crucial buffer, preventing sudden and potentially dangerous transitions between the red and green phases. 7 Brief History of Traffic Signals A brief history of the Traffic signals. Traffic signals have come a long way. Today, traffic signals have become highly sophisticated, incorporating sensors, cameras, and advanced control systems. These intelligent signals can detect vehicle presence, adjust timings based on real-time traffic conditions, and even prioritize certain modes of transportation like buses or pedestrians 8 IMSA Traffic Signal Technician I Agencies and Manuals 9 3  6/26/2024 Governing Agencies and Manuals FHWA (Federal Highway Administration) MUTCD (Manual of Uniform Traffic Control Devices) ◦ Uniformity and Consistency, safety, legal compliance, and efficiency and traffic flow. OSHA (Occupational Safety and Health Administration ◦ Worker Safety, Standard Setting, Compliance and Enforcement, whistleblower protection. ◦ SDS sheets – safety data sheets for chemicals NEC (National Electric Code) ◦ Electrical Safety, National Standards, Electrical System Design, and Installation and Maintenance. 10 Governing Agencies and Manuals NEMA (National Electrical Manufacturers Association ◦ Standardization, Safety and Reliability, and Technical Expertise. IMSA (International Municipal Signal Association) NESC - National Electrical Safety Code CALTRANS/170 (California Department of Transportation) ITE (Institute of Transportation Engineers) ATCC – Advanced Transportation Controller Cabinet ATC - Advanced Transportation Controller 11 Manual of Uniform Traffic Control Devices - MUTCD Part 4 of the MUTCD is all about Highway MUTCD Traffic Signals. This is the reference guide to the United States federal rules regarding Warranting, Construction, Maintaining and Inspecting traffic signals. Standards for traffic control signals are important because traffic control signals need to attract the attention of a variety of road users, including those who are older, those with impaired vision, as well as those who are fatigued or distracted, or who are not expecting to encounter a signal at a particular location. This Manual ensures uniformity across the United States and Canada (MUTCDC). 12 4  6/26/2024 Occupational Safety and Health Administration OSHA stands for the Occupational Safety and Health Administration. It is a federal agency within the United States Department of Labor. OSHA's primary mission is to ensure safe and healthy working conditions for employees across various industries in the United States. Here are some key aspects of OSHA: 1. Workplace Safety Standards 2. Inspections and Compliance 3. Training and Education 4. Recordkeeping and Reporting 5. Whistleblower Protection 6. Partnerships and Collaboration 13 Safety Data Sheets (SDS) In 2003, the UN adopted the Globally Harmonized System of Classification & Labeling of chemicals. An internationally agreed upon system of standardized chemical hazard classification & communications. SDS sheets offer safety information for chemicals you may use in your work environment. SDS sheets follow a 16-section format: Section 1 – product identification Section 9 – physical & chemical properties Section 2 – hazard identification Section 10 – stability & reactivity Section 3 – composition of ingredients Section 11 – toxicological information Section 4 – first aid Section 12 – Ecological information Section 5 – firefighting measures Section 13 – disposal considerations Section 6 – accidental release measures Section 14 – transportation information Section 7 – handling & storage Section 15 – regulatory information Section 8 – exposure controls / PPE Section 16 – other information not covered above 14 National Electrical Code Handbook The National Electrical Code (NEC) Handbook is a comprehensive guidebook that provides detailed interpretations, explanations, and additional information to accompany the National Electrical Code. The NEC Handbook is published by the National Fire Protection Association (NFPA), which is responsible for developing and updating the NEC. The NEC Handbook offers the following features: 1. Commentary 2. Examples and Illustrations 3. Case Studies 4. Historical Information 5. Cross-References and Index 15 5  6/26/2024 National Electrical Safety Code - NESC The NESC covers a wide range of topics, including: 1. General Requirements 2. Safety Rules for the Installation and Maintenance of Electric Supply Stations and Equipment 3. Safety Rules for the Installation and Maintenance of Overhead Electric Supply and Communication Lines 4. Safety Rules for the Installation and Maintenance of Underground Electric Supply and Communication Line 5. Work Rules for the Operation of Electric Supply and Communication Lines and Equipment 16 National Electrical Manufacturers Association The National Electrical Manufacturers Association was founded in 1926, NEMA is an ANSI-accredited Standards Developing Organization made up of business leaders, electrical experts, engineers, scientists, and technicians. NEMA convenes a neutral forum for Members to discuss industry-wide concerns and objectives under a legal umbrella by trained NEMA Staff NEMA 17 Knowledge Check: Multiple Choice Which document determines the hierarchy of utilities on a utility pole? a) MUTCD b) NEC c) NESC d) OSHA 18 6  6/26/2024 Knowledge Check: Multiple Choice Part four of the __________ determines all the guidance for traffic signals. a) MUTCD b) NEC c) NESC d) OSHA 19 Traffic Signal Technician I Lesson 1: Liability / Legal Responsibility 20 Tort Law & Liability According to The Babcock Law Firm LLC “ Briefly and generally speaking, the term “Tort Law” encompass legal situations where an individual could be held liable for an injury inflicted upon another person. Tort law cases also involve the injured party seeking compensation for any damages they have experienced (property loss, physical harm or pain and suffering)." 21 7  6/26/2024 Tort Liability What this means to you: Your goal at the end of the day is to get home safely and you are not the only one. Thousands of drivers come through your city on a daily basis, all of whom have a destination in mind. The main part of your job is to keep the transportation infrastructure functioning and to quickly respond to any issues that may arise. Which is why it is extremely important that you A. Do your job fully, do not cut corners. B. Set up a proper work zone C. Do not leave something that is not functioning properly out in the field. 22 Tort Liability 23 Knowledge Check: Multiple Choice Which statement about negligence is correct? a) Failure to use exact care in one’s actions b) Failure to use reasonable care in one's actions c) Failure to act in one’s best interest d) Failure to act on behalf of the public 24 8  6/26/2024 IMSA Traffic Signal Technician I Lesson 2: PPE and Work Zone safety 25 PPE and Work Zone Safety http://www.youtu be.com/watch?v= nbOco34z- HY&feature=emb _err_woyt Must be viewed on YouTube. Click the arrow. 26 PPE and Work Zone Safety 27 9  6/26/2024 PPE and Work Zone Safety Personal Protective Equipment (PPE) refers to specialized equipment and clothing worn by individuals to protect themselves from potential hazards and risks in the workplace or other environments. The importance of Personal Protective Equipment can be summarized as follows: Worker Safety. Hazard Mitigation Legal and Regulatory Compliance Risk Reduction Confidence and Productivity Containment and Prevention of Hazard Spread Emergency Preparedness: https://www.temporarytrafficsignals.com/safety 28 Personal Protection Equipment Personal Protection Equipment you will find as a Signal Tech would be: Hard Hat Safety Glasses Insulated gloves Work Boots / safety toe High Visibility Retroreflective Safety Vest Fall Protection (Harness) With an SRL or shock absorbing lanyard 29 Personal Protection Equipment Electrical safety gloves, also known as insulating gloves, are a critical piece of Personal Protective Equipment (PPE) for traffic signal technicians and anyone working around energized electrical equipment. They protect the wearer from electrical shocks and burns by providing insulation from electrical current. Electrical safety gloves are classified by the level of voltage protection they provide and are subject to strict standards. In the United States, these standards are set by the American Society for Testing and Materials (ASTM). Here are the classifications:  Class 00: Max use voltage of 500 volts AC, 750 DC  Class 0: Max use voltage of 1,000 volts AC,1500 DC  Class 1: Max use voltage of 7,500 volts AC, 11,250 DC  Class 2: Max use voltage of 17,000 volts AC, 25,500 DC  Class 3: Max use voltage of 26,500 volts AC, 39,750 DC  Class 4: Max use voltage of 36,000 volts AC, 54,000 DC 30 10  6/26/2024 Personal Protection Equipment  All rubber insulating gloves must be professionally tested and recertified semi-annually or quarterly.  Low-voltage gloves, class OO or O should be tested semi-annually  High-voltage gloves, class 1 and above should be tested quarterly  Every glove should be field tested before each use:  Roll the cuff shut and inflate the glove with trapped air.  Check for any air leaks.  If leaking air is found, DO NOT USE THE GLOVE!!!  Class 00: Max use voltage of 500 volts AC, 750 DC  Class 0: Max use voltage of 1,000 volts AC,1500 DC  Class 1: Max use voltage of 7,500 volts AC, 11,250 DC  Class 2: Max use voltage of 17,000 volts AC, 25,500 DC  Class 3: Max use voltage of 26,500 volts AC, 39,750 DC  Class 4: Max use voltage of 36,000 volts AC, 54,000 DC 31 Work Zone Safety Work zone safety refers to the measures and practices implemented to ensure the safety of workers, motorists, pedestrians, and equipment in construction or maintenance work zones on roadways. Key aspects of work zone safety include: Traffic Control: Proper traffic control measures, including signs, cones, barricades, and flaggers, are essential for directing traffic safely through work zones. Clear and visible signage informs drivers of upcoming changes, lane closures, speed limits, and potential hazards. Sections of the work zone include the advanced warning area, the transition area, the activity area, and the termination area. Flaggers must always remain in their flagging positions (not like this though). DO NOT LEAVE YOUR FLAGGING POSITION. Communication: Effective communication between workers and motorists is critical to ensure awareness of potential dangers and changes in traffic flow. Communication methods such as radio communication, electronic message boards, and temporary signage help convey important information to drivers and workers. 32 Work Zone Safety Key aspects of work zone safety include: Work Zone Layout: The design and layout of work zones should be carefully planned to optimize safety. This includes providing adequate space for equipment and workers, maintaining proper sight distances, and minimizing conflicts between different modes of transportation. Work zones outside the traveled roadway seldom require formal traffic control. Personal Protective Equipment (PPE): Workers in work zones must wear appropriate personal protective equipment, such as high-visibility clothing, hard hats, safety glasses, gloves, and safety footwear. PPE helps protect workers from potential hazards and increases their visibility to motorists. Speed Management: Reduced speed limits are often implemented in work zones to ensure the safety of workers and drivers. Speed reduction measures such as speed bumps, speed enforcement, and speed display devices help promote compliance with posted speed limits. 33 11  6/26/2024 Work Zone Safety The first thing that can lead to a legal issue would be an improper work zone. Traffic signal work zones, due to their nature, are inherently risky environments with various safety issues. Here are some of the unsafe traffic control issues that can be identified in these work zones: Inadequate Signage Lack of Buffer Space Inadequate Lighting Inefficient Traffic Control Devices: (faded signs, non-reflective cones) Lack of Protection for Pedestrians, Cyclists, and workers https://driving-tests.org/ 34 Work Zone Safety Setting up an appropriate work zone for traffic signal repair or maintenance requires a variety of parts and devices to ensure the safety of both workers and motorists. The main goal is to divert traffic effectively and safely around the work zone. Here's a list of necessary parts and devices: Traffic Cones and Barrels Signs Barricades Arrow Boards or Variable Message Signs Temporary Traffic Signals Flaggers High-Visibility Clothing Lighting Devices Tapering Devices Temporary Pavement Markings https://weeklysafety.com/blog/temporary-traffic-control-signs-and-devices 35 Traffic Conditions High-Traffic Areas Low-Traffic Areas Examples of high-traffic areas include Examples of low-traffic areas include high-volume streets, such as arterials. low-volume streets, such as a local streets or These types of streets are typically collector streets. These types of streets are wide and have multiple lanes of travel. typically narrow and have single lanes of travel. 36 12  6/26/2024 Pedestrian Conditions Ensure safe pedestrian conditions for all nearby crosswalks. Potential unsafe pedestrian conditions: 1. Obstructed walking paths 2. Potential hazards that should be removed 3. Unsecured work area 37 Overhead Safety “Look up and live” is a saying for a reason: Overhead power lines can be deadly; therefore, care must be taken when working near these lines. OSHA mandates that you MUST maintain a minimum of 10 foot of clearance from overhead power lines (table “A”) https://www.osha.gov/laws-regs/regulations/standardnumber/1926/1926.1408 Understand how power poles are constructed: The highest voltage lines will be at the top of the pole Potential voltages on lines reduce as you come down the pole Communications lines will be the lowest lines on the pole Look for “risers” on poles as overhead utilities may transition to become underground utilities 38 Arc Flash An arc Flash is an electrical explosion with a tremendous amount of pressure and heat. Everything turns into molten metal upwards of 35,000 degrees The video is in “VERY” slow motion… 39 13  6/26/2024 Underground Safety “Call before you dig” is another saying for a reason: Underground utilities present even more hazards” The locate identification colors are as follows: Electric power lines Natural gas line Petroleum lines Steam lines Water lines Sanitary sewer lines and storm drain lines Communication lines to include phone, cable TV, and fiber optic Military and private underground facilities – not specified Surveying Proposed excavation - White 40 Knowledge Check: Fill the Blanks Fill in the blanks with the correct words from the box below: arterials multiple single narrow larger collectors a) High-traffic areas include high-volume streets, such as ___________, and have ___________ lanes of travel and require a ___________ work zone. b) Low-traffic areas include low-volume streets, such as ___________, and are typically ___________ and have ___________ lanes of travel. 41 Knowledge Check: Multiple Choice Which electrical gloves would you use to work near voltages of 15,240 VAC ? a) Class 0 b) Class 1 c) Class 2 d) Class 3 42 14  6/26/2024 IMSA Traffic Signal Technician I Lesson 3: Signal Technician Tools 43 Multimeter A digital multimeter (DMM) is a versatile tool used for electrical troubleshooting and maintenance. It can measure voltage, current, resistance, and a host of other things allowing technicians to test and diagnose electrical issues in traffic signals and roadway lighting systems. 44 Insulated Tool Set Dielectric (insulated) Hand Tools: These include screwdrivers, pliers, wire strippers, and other tools with insulated handles. They are designed to protect the user from electric shock when working with live circuits or components. Make sure you know what voltage the insulated tools are rated for. Inspect the insulated handles for any cracks, cuts, nicks, or damage that may compromise electrical safety. 45 15  6/26/2024 Utility Locating Equipment Very often, signal technicians will need to locate underground traffic signal utilities. Locating equipment may offer: Multiple frequencies for directly connecting to a utility Multiple frequencies for inducing a https://www.acoi.us/3m-product signal onto a utility Signal Sensitivity & Gain control Directional locating features Mapping modes 46 Insulating Mats or Blankets Insulating Mats or Blankets: These can provide a safe area to stand or place tools when working on electrical systems. 47 Related Traffic Signal Test Equipment Load Tester – used to verify the integrity of batteries Fiber Power meter – used to measure the light loss in a fiber LCR Meter – measures inductance, capacitance, & resistance TDR/OTDR – measures anomalies in a wire or optical fiber Megohmmeter – measures conductor insulation resistance Loop Tester – measures inductance and frequency Ground Rod Tester – measures resistance to ground Voltage tester (loaded) – looks for voltage on a conductor Tone Generator – place an audible signal on a conductor to locate MMU / CMU Tester - (certification tester) BIU Tester – certification tester for the BIU’s Load Switch Tester – verifies the integrity of a load switch 48 16  6/26/2024 Knowledge Check: Multiple Choice Which meter would you use to check resistance? a) An LCR meter b) A megohmmeter c) A load tester d) A multimeter 49 IMSA Traffic Signal Technician I Lesson 4: Electrical Theory 50 Basic Electrical theory Electrical Safety Conductors and Insulators Ohms Law AC / DC Series / Parallel Grounding and Bonding 51 17  6/26/2024 Basic Electrical Theory Electrical Safety Electricity is Dangerous!!! 30,000 non-fatal shock accidents per year Nearly 7 kids /day are treated in the ER for electrical shocks or burns (wall outlets) Estimated 60 electrocutions / yr. because of consumer products 152 out of 5,190 worker deaths were caused by electrocution (2021) 52 Electrical Safety - High Voltage Dragons 53 Basic Electrical Theory Electrical Safety Electricity is Dangerous!!! Traffic signal technicians may be required to work on components or wiring while energized or (hot). Using insulated tools, non- conductive tools and wearing gloves can reduce the chances of getting shocked by isolating you from the Don’t Complete the Circuit! circuit. Also, your freehand should not be touching the cabinet, pole or any other grounded device. 54 18  6/26/2024 Basic Electrical Theory Conductors and Insulators Conductors are materials that conduct electricity. Most metals are conductors. Copper is the most used material for electrical wiring. Aluminum is also used for electrical wiring Gold and silver are better conductors than copper but are much too expensive to use for wire, however these materials are used in electronics. 55 Basic Electrical Theory Conductors and Insulators Insulators are materials that do not conduct electricity. Some materials commonly used as insulators are various types of plastics, rubber, glass, porcelain, and ceramic. https://electricalschool.org/ 56 Basic Electrical Theory Ohms Law Understanding electricity Electricity flowing through wires (conductors) is similar as water flowing through pipes. Voltage is like Water Pressure Current is like the amount of water flowing Resistance is like the size of the pipe Power is the amount of energy consumed 57 19  6/26/2024 Basic Electrical Theory Ohms Law Voltage, Current & Resistance: The basis for Ohms Law A ratio comparison that we use as a formula E = I x R ◦ E = Voltage (Electromotive Force) (Volts) ◦ I = Current (Intensity) (Amps) ◦ R = Resistance (Ohms) 58 Basic Electrical Theory Ohms Law OHMS LAW There are multiple voltages typically used in traffic signal circuits 120 VAC, 24 VDC, 12VDC, E=IxR 12VAC, 48 VDC, & 3-5 VDC These voltages normally remain the same. I=E/R The amount of current flowing in a circuit is R=E/I determined by the resistance and the voltage. If you increase the voltage and the resistance E = Voltage (Electromotive remains the same the current will increase. Force) (Volts) If you decrease the resistance and the voltage I = Current (Intensity) (Amps) remains the same the current will increase. R = Resistance (Ohms) For example, if you add another signal indication to a circuit, that reduces the resistance of that circuit, and the current will increase.(The voltage remains the same) 59 Basic Electrical Theory Power Formulas Power Formulas There are multiple voltages typically used in traffic signal circuits 120 VAC, 24 VDC, 12VDC, P=IxE 12VAC, 48 VDC, & 3-5 VDC These voltages normally remain the same. I=P/E The amount of current flowing in a circuit is E=P/I determined by the resistance and the voltage. The amount of power consumed by a circuit is a P = Power (Watts) function of Voltage times Current E = Voltage (Electromotive All electrical equipment and circuits are based on Amps x Volts = Watts Force) (Volts) how much power will be consumed. I = Current (Intensity) (Amps) Watts / Volts = Amps Watts / Amps = volts 60 20  6/26/2024 Basic Electrical Theory AC / DC Electric Current Electric current flows in two ways, as an Alternating Current (AC) or Direct Current (DC). The main difference between AC and DC lies in the direction in which the electrons flow. In DC, the electrons flow steadily in a single direction, while electrons keep switching directions, going forward and then backwards in AC. 61 Basic Electrical Theory AC / DC AC – Alternating Current Alternating current AC is the type of electricity that powers our homes businesses and factories and our traffic signals. It is generated by various types of generators and distributed through the power grid. It is typically 120 volts and alternates at 60 cycles per second (60 Hertz) 62 Basic Electrical Theory AC / DC DC – Direct Current Direct Current DC is produced by batteries or power supplies. Electronic circuits and devices run on DC. Typical voltages used in electronics are 5 Volts, 12 Volts, and 24 Volts. 63 21  6/26/2024 Basic Electrical Theory Series / Parallel Schematic Symbols 64 Basic Electrical Theory Series / Parallel / Combination Resistive loads connected in parallel Resistive loads connected in series Resistive loads connected in combination 65 Basic Electrical Theory Series In a series circuit the current remains constant because it only has one path to flow in the circuit. Voltage drops across each load. Total voltage: ET = E1 + E2 + E3… The total resistance in the circuit adds up from each load. Total resistance: RT = R1 + R2 + R3… The total power adds up from all the loads Series Connection PT = P1 + P2 + P3… 66 22  6/26/2024 Basic Electrical Theory Parallel In a Parallel circuit voltage remains constant. Traffic signal indications are wired in parallel. Current adds up from each branch: IT = IBranch1 + IBranch2 + IBranch3… Total resistance reciprocates from all the branch loads. RT = … Parallel Connection The total power adds up from all the loads PT = P1 + P2 + P3… 67 Basic Electrical Theory Series/Parallel or Combination A combination circuit has both series loads and parallel loads. Circuits must be broken down into its simplest form Rules from both types of circuits must be used: Series rules for the series loads Parallel rules for the parallel loads The total power adds up from all the loads PT = P1 + P2 + P3… Series/Parallel Connection Traffic signal cabinets have some series/parallel circuits on the power panels. 68 Basic Electrical Theory Grounding and Bonding Bonding Article 100 of the NEC defines bonded (bonding) as “connected to establish electrical continuity and conductivity.” Bonding metal parts, such as enclosures and raceways, ensures that they are all continuous on an effective ground-fault current path (EGFCP) that references back to ground (earth). The EGFCP helps operate devices such as circuit breakers and fuses or ground-fault detectors in ungrounded systems. 69 23  6/26/2024 Basic Electrical Theory Grounding and Bonding Bonding In grounded systems, it is important to bond the equipment grounding conductors to the system grounded conductor to complete the EGFCP back to the source of electricity. The conductivity of the EGFCP is critical for protective devices to work properly. This speaks to why we scrape the paint from contact surfaces of metallic enclosures to make our electrical system bonding connections. Removing the paint, as required in Section 250.12, provides for a better connection and conductivity path. 70 Basic Electrical Theory Grounding and Bonding Grounding The NEC defines ground as “the earth.” Grounding is a conductive connection, intentional or accidental, between a circuit or electrical equipment and the ground or some conductive object acting as the ground. In an airplane, for example, the fuselage acts as the ground 71 Basic Electrical Theory Grounding and Bonding Grounding and Bonding Section 250.4 states the general requirements for grounding and bonding of electrical systems for both grounded and ungrounded systems. For grounded systems, the NEC requires you to perform all of the following: electrical system grounding, electrical equipment grounding, electrical equipment bonding, and bonding of electrically conductive materials. In ungrounded systems, the same actions are required except for electrical system grounding. When these NEC requirements are implemented, an effective ground-fault current path is created, which is your desired end goal. 72 24  6/26/2024 Schematic Diagrams A schematic diagram is a map of electrical circuits that uses standardized symbols to show how electricity flows through the circuit. In traffic signal work for example, a schematic diagram would show the electronic components, such https://www.britannica.com/ as resistors, capacitors, & IC chips on a printed circuit board inside the controller or MMU… 73 Wiring Diagrams A wiring diagram or circuit diagram is also a map that shows every component as a graphical representation and the electrical connections within the circuit for wiring purposes. In a traffic signal cabinet, a wiring diagram would show the load switch, FTR’s, & flasher sockets, the field terminals, the BIU sockets, and all the components on the power distribution panel and all the wiring connections between them. 74 Generic NEMA TS-1 Wiring Diagram This is a generic wiring diagram for a NEMA TS-1 cabinet. It illustrates how power enters the cabinet (far right) Flows through out the cabinet And feeds the signal heads in the field (lower left). 75 25  6/26/2024 Knowledge Check: Matching Activity The left column shows electrical component. The right column shows the explanation of those components. Match each component with the explanation. a) Voltage 1) Size of the pipe b) Current 2) Water pressure c) Resistance 3) Energy consumed d) Power 4) Water flow 76 Knowledge Check: Matching Activity The left column shows electrical component. The right column shows the unit of measure for those components. Match each component with the correct measurement. a) Electrical pressure 1) Amps b) Current 2) Watts c) Resistance 3) Volts d) Power 4) Ohms 77 Knowledge Check: Multiple Choice Ohms law is based on the following formula: a) E = I x P b) E = I x R c) E = R x P d) I = E x P 78 26  6/26/2024 Knowledge Check: Matching Activity The left column shows electrical circuit. The right column shows the rule to be true in those circuits. Match each circuit with the correct rule. a) Voltage remains the same 1) Series Circuit b) Current remains the same 2) Parallel Circuit c) Resistance adds up 3) Combination Circuit d) Power adds up 79 Knowledge Check: Multiple Choice Bonding & grounding means to: a) Bond everything to ground b) Bond everything to a difference of electrical potential and then ground it c) Bond everything to the same electrical potential and then ground it d) Bond everything to each other purpose of bonding is to ensure that all conductive objects in an electrical system are at the same potential 80 IMSA Traffic Signal Technician I Lesson 5: Traffic Signal Operational Concepts 81 27  6/26/2024 Traffic Warrants Warrant: The investigation of the need for a traffic control signal shall include an analysis of factors related to the existing operation and safety at the study location and the potential to improve these conditions, and the applicable factors contained in the following traffic signal warrants: Warrant 1, Eight-Hour Vehicular Volume Warrant 2, Four-Hour Vehicular Volume Warrant 3, Peak Hour Warrant 4, Pedestrian Volume Warrant 5, School Crossing Warrant 6, Coordinated Signal System Warrant 7, Crash Experience Warrant 8, Roadway Network \Warrant 9, Intersection Near a Grade Crossing 82 Traffic Warrants 83 Engineering Study / Engineering Judgement Engineering Study: Study of traffic conditions, pedestrian characteristics, and physical characteristics of the location shall be performed to determine whether installation of a traffic control signal is justified at a location. Engineering Judgement: It involves using technical knowledge, principles, and practical judgment to address complex issues and balance various factors in the context of traffic planning, design, operation, and safety. Some examples; 1. Traffic Signal Timing 2. Roadway Design 3. Traffic Impact Assessments 4. Safety Analysis 5. Intelligent Transportation Systems (ITS) 6. Traffic Control Measures 84 28  6/26/2024 Traffic Signal Operation Theory Flow of traffic at a signalized intersection Controlling the flow of traffic at a signalized intersection requires a two-step process: Step #1 – Each movement of approaching traffic to be controlled by the traffic signal is assigned a “phase” number https://www.google.com/ Step #2 – all the phases must somehow work in unison with each other 85 Step #1 – The Vehicle Phase Phase - This intersection has four vehicle A group of controller timing intervals and approaches controlled with two vehicle settings used to control one movement of phases traffic at a signalized intersection. Typical vehicle movements that are controlled by the signal are: Straight thru movements Left turn movements Right turn movements Vehicle phases are symbolized with “” Vehicle phases are also assigned numbers, typically 1 thru 8 86 Step #2 - Rings and Barriers Ring - Barrier - NEMA defined a ring as: “A ring Otherwise known as a “compatibility line” is defined by NEMA as “A reference point in the consists of two or more sequentially timed preferred sequence of a multi-ring controller in and individually selected conflicting phases which all rings are interlocked.” so arranged as to occur in an established Which means the rings must work together by order”. crossing the barrier at the same time Each ring is sequentially timed which Phases on one side of the barrier will never means phases in the same ring will operate with phases on the other side of the NEVER be compatible: I.E., always barrier “conflicting” THE RING CONTROLS EVERYTHING 87 29  6/26/2024 Traffic Signal Operation Theory Assignment of Phases to Movements of Traffic Standard NEMA phasing: R1 1 2 3 4 Odd phase numbers are assigned to the left turn movements; 1,3,5,& 7 R2 5 6 7 8 Even phase numbers are assigned to the thru Standard 8 phase ring sequence movements; 2,4,6,& 8 Phases 1,2,5,6 are assigned to the Main street 2 5 movements Phases 3,4,7,8 are assigned to the side street movements 4 Phases rotate around the intersection in a clockwise direction 3 7 ◦ Phase rotation counts the left turn movements 8 separately from the thru movements Compatible and conflicting phase numbers are assigned to compatible and conflicting vehicle 6 N 1 movements 88 Traffic Signal Operation Theory Assignment of Phases to Movements of Traffic The 4 phases assigned to the main street R1 1 2 3 4 is called a concurrent group. 1-2-5-6 R2 5 6 7 8 3-4-7-8 make up the side street Standard 8 phase ring sequence concurrent group Barriers divide the concurrent groups 2 5 A concurrent phase can be on with 4 another phase in its concurrent group. 3 7 1 or 2 can be on with 5 or 6. 8 3 or 4 can be on with 7 or 8. N 1 6 89 Traffic Signal Operation Theory Pedestrians Pedestrians MUST be protected from any conflicting vehicle movements that may cross their path. For example, a pedestrian crossing the west side of the intersection (north to south): Pedestrians must cross with compatible phases: ◦ That eliminates the side street concurrent group, ’s 3, 4, 7, & 8 The pedestrian cannot cross the street with 1 active ◦ 1 is compatible with 5 and 6. Therefore ’s 5 and 6 are also eliminated for this pedestrian movement, however 5 is compatible with 2 per the ring. Therefore, the only active vehicle phase that is allowable to safely cross the pedestrian is 2. 90 30  6/26/2024 Traffic Signal Operation Theory Lead / Lag Phases R1 Leading phases are defined as the 1 2 3 4 first phase(s) serviced once you R2 5 6 7 8 cross a barrier Standard 8 phase ring sequence Leading / Lagging are specifically referred to the left turn movements 2 5 In the example at the right, the first 4 phases serviced once a barrier is crossed are the left turn movements 3 7 8 ◦ Leading left turn movements N 1 6 91 Traffic Signal Operation Theory Lead / Lag Phases R1 2 1 4 3 Leading phases are defined as the first phase(s) serviced once you 6 5 8 7 R2 cross a barrier Standard 8-phase ring sequence Leading / Lagging are specifically referred to the left turn movements 2 5 In the example at the right, the first 4 phases serviced once a barrier is crossed are the thru movements 3 7 8 ◦ Lagging left turn movements N 1 6 92 Lead-Lag Phases R1 Lead-Lag Left-Turns 2 1 4 3 R2 5 6 7 8 During this operation, leading left-turn Standard 8-phase ring sequence phasing and lagging left-turn phasing are provided on opposing approaches 2 5 of the same street. This operation produces independence between the 4 through phases, being desirable under coordinated operations, and to 3 7 accommodate platoons of traffic 8 arriving from each direction at different times. N 1 6 93 31  6/26/2024 Split Phasing Split Phase Left-Turns R1 2 1 4 3 During this operation, all movements of a R2 5 6 7 8 particular approach are serviced – thru, left Standard 8-phase ring sequence turn, & right turn. Followed by the servicing of all movements of the opposing approach. For example: Following the ring sequence at the right: ◦ South and South left turn ◦ North and North left turn ◦ West and West left turn ◦ East and East left turn 94 Protected and Permissive Phases Protected Phase: Protected phases provide exclusive right-of-way to a specific movement, allowing vehicles or pedestrians to proceed with no conflicting traffic. Permissive Phases: Permissive phases allow a movement to proceed with caution when there is a gap in conflicting traffic. These phases typically involve yielding or giving right-of-way to opposing or crossing traffic. Protected Phase Protected / Permissive Phase 95 Overlaps Overlaps: A GREEN indication that allows a movement of traffic to flow during the GREEN and clearance intervals of one or more phases. Think of an overlap as a “clean-out”. This is an area of the intersection that you do not want traffic backing up, thus prohibiting the movement of other vehicle phases. An overlap helps you gain more efficiency in the flow of traffic thru a signalized intersection. NEMA defined four overlaps; “A”, “B”, “C”, & “D” 96 32  6/26/2024 Overlaps Overlaps: When can the SB GREEN right turn arrow be displayed without conflicting with other movements of traffic? The overlap must work within the ring diagram to avoid conflicts Any vehicle legally traveling in the WB lane while the SB right turn has a GREEN arrow Overlaps may be displayed in the ring diagram There are two types of overlaps: “Parent / Child” “Independent” or “Timed Overlaps” 97 “Parent / Child” Overlaps Two types of Overlaps: The overlap indication begins with one phase and terminates with another phase In this case, the overlap “A” (the child) is controlled by phases 2 and 3, the parents 1. Phase 2 begins timing GREEN / Overlap A goes GREEN 2. Phase 2 times YELLOW clearance / Overlap A stays GREEN 3. Phase 2 times RED clearance / Overlap A stays GREEN 4. Phase 3 begins timing GREEN / Overlap A stays GREEN 5. Phase 3 times YELLOW clearance / Overlap A turns YELLOW 6. Phase 3 times RED clearance / Overlap A turns RED 98 “Independent” or “Timed” Overlaps Two types of Overlaps: The overlap indication begins with one phase but does not terminate with the other phase This overlap has its own timing parameters In this case, the overlap “A” (the child) is controlled by phases 2 and 3, the parents…however, 1. Phase 2 begins timing GREEN / Overlap A goes GREEN 2. Phase 2 times YELLOW clearance / Overlap A stays GREEN 3. Phase 2 times RED clearance / Overlap A stays GREEN 4. Phase 3 begins timing GREEN / Overlap A stays GREEN 5. Phase 3 times YELLOW clearance / Overlap A begins timing its GREEN time 6. Phase 3 times RED clearance / Overlap A continues timing its GREEN time 7. Overlap then times its YELLOW and RED clearance times 99 33  6/26/2024 Traffic Signal Operation Types Fully-Actuated Operation: In fully-actuated operation, detection is provided to all the phases at an intersection. Semi-Actuated Operation: In semi-actuated operation, detection is provided to the phases controlling the minor movements and the left turn movements at an intersection. Pre-timed / Coordinated Operation: Pre-timed operation provides a predetermined cycle length, regardless of flow of traffic or pedestrians. There may be vehicle or pedestrian detection. 100 Recalls Recalls are operational options that sends internal inputs into the controller to place a constant demand for service on any given phase(s). The controller will service recalls in every cycle regardless of vehicle or pedestrian demand. There are multiple types of recall. The three most common are: Minimum (Min) recall: minimum recall puts a demand for vehicle service on any given phase(s). Once the controller services the phase, it begins timing minimum GREEN interval. Maximum (Max) recall: Max recall puts a demand for vehicle service and forces the controller to time the MAX I, II, or III interval. The phase(s) will remain in a GREEN condition for the maximum amount of time regardless of traffic flow. Pedestrian (Ped) recall: Ped recall puts a demand for pedestrian service on a phase(s) and forces the controller to time the Walk and the Flashing Don’t Walk intervals each time the controller services the phase(s). 101 Signal Intervals and color phases Signal Intervals: The Interval is the time allocated to each color (Red, Yellow, Green, Walk, Don’t Walk) to remain illuminated before transition to the next phase. The duration is crucial in regulating the movement of vehicles and pedestrians at an intersection, ensuring smooth traffic flow and minimizing conflicts. The length of each interval can vary depending on local traffic engineering standards and the specific needs of the intersection. 102 34  6/26/2024 Signal Intervals and color phases Calculating signal intervals: 1)Turning movement counts – collecting data on traffic volumes at intersection. This includes Pedestrians and cyclist. This will help determining peak times in which is the highest volume of traffic at a given time of day. 2)Signal Phasing – Determine the number and direction of movements that need to be accommodated. 3)Minimum Green Time – Minimum green is the guaranteed amount of time for a particular phase. Its purpose is to get the queue of vehicles moving into the intersection once the phase turns green. 4)Pedestrian Clearance Time – Pedestrian Intervals calculated to allow safe crossing by pedestrians and cyclists. This varies based on width of road and crosswalk and Pedestrian Volume 103 Signal Intervals and color phases Calculating signal intervals: 1. Yellow Clearance Interval – The yellow intervals are warnings to drivers that the associated green indication has ended, and the right-of- way is about to change. The length of the Yellow interval is typically based on driver PRT (Perception-reaction time) and the distance to safely stop the vehicle, however it will never be anything less than 3.0 seconds. 2. Red Clearance Interval - is added to allow vehicles to clear the intersection before moving conflicting cross-traffic. 3. Coordination – In cases where multiple traffic signals are along a corridor, signals can be coordinated to allow for vehicles to travel smoothly through multiple intersections. 104 Cycle Length Cycle length is total time of all phases combined Cycle Length: In traffic signals, cycle length refers to the total time taken for a complete sequence of signal indications. It represents the duration required for the signal to go through all its programmed phases, including the green, yellow, red, walk and flashing don't walk intervals for all movements per the ring diagram at an intersection. 105 35  6/26/2024 Splits and Offsets Split is time Allowed to one phase at a time Split: A "split", as defined by NEMA refers to the segment of the cycle length allocated to each phase that MAY occur. It represents the duration or percentage of the total cycle length that is dedicated to a particular signal phase, allowing vehicles or pedestrians in that movement to proceed. The split can be expressed as a percentage or a number of seconds of the total cycle length. For example, if a cycle length is 120 seconds and the split for a specific movement is 20 seconds, the split would be 20/120 or 16.67% of the cycle length. This means that the signal phase associated with that movement could be active for 20 seconds within each cycle. 106 Split and Offsets Offset: Offset is the time relationship, expressed in seconds or percent of cycle, determined by the difference between a defined point in the coordinated green and a system reference point. For that reason, it is imperative that the clock and calendar always be kept with the proper date & time. Most agencies traffic systems automatically synchronize the date and time every 24 hours. The last thing you always do before leaving a traffic signal cabinet, is to verify the date and time in the controller and monitor if so equipped. Effective offset coordination can help reduce stops, improve travel times, enhance fuel efficiency, and enhance the overall capacity and performance of the road network. However, it is important to note that offsets change throughout the day with coordination pattern changes. 107 Knowledge Check: Multiple Choice Which statement is correct about standard NEMA phasing? a) Phases count in a counter-clockwise direction b) Even phase numbers are assigned to the left turn movements c) Phases 1, 2, 5, & 6 are assigned to the side street d) Phases 3, 4, 7, & 8 are assigned to the main street 108 36  6/26/2024 Knowledge Check: Multiple Choice A ring is defined as: They literally Chopped a) Two or more sequentially timed up the definition from b) Individually selected 87 ALL are Correct WTF Dumbest Shit c) Conflicting phases ever!!!!!!!!!!! d) Arranged to occur in an established order 109 Knowledge Check: Multiple Choice What best describes a barrier? a) An obstacle preventing vehicles from entering a closed lane b) An interlock in a multi-ring controller c) It forces conflicting phases into concurrent timing d) Phases in each ring must cross the barrier at the same time 110 Knowledge Check: Fill the Blanks Fill in the blanks with the correct words from the box below: Lead Protected Semi-actuated Parent/child overlap Lag Permissive Fully Actuated Timed overlap Protected Lead a) Left turn on a green arrow only is a ______________ phase which may be the ___________ phase once the barrier is crossed. Parent/child overlap b) A ________________ will terminate after its controlling phase has terminated which may operate as either a _____________ Timed overlap or _____________ Permissive phase. 111 37  6/26/2024 Knowledge Check: Fill the Blanks Fill in the blanks with the correct words from the box below: Semi-actuated Parent/child overlap Permissive Fully Actuated Permissive a) A flashing yellow arrow operates as a ______________ phase in an intersection that is _______________ because there is no vehicle detection on the main street movements. Semi-actuated Fully actuated b) An intersection that operates with vehicle detection on all approaches is _____________. c) A movement of traffic that is controlled by two or more phases is known as __________________. Parent/Child Overlap 112 Knowledge Check: Multiple Choice A complete sequence of signal indications is better known as a: a) Split b) Offset c) Cycle length d) An interval 113 Traffic Signal Technician I Lesson 6: Controller Assembly - Cabinet Components 114 38  6/26/2024 Lesson Introduction - Cabinets and Components Controller Detectors and Sensors Power Supply Communication Devices Circuit Boards / Back Panel Signal Conflict Monitor / MMU Traffic Signal Heads Battery Backup Systems Flashing Beacons Surge Protection Devices 115 Introduction to Cabinets Essentially Six basic types of cabinets & controllers Electrical Mechanical Pre-NEMA NEMA TS1 – Military style “A”, ”B”, ”C” and sometimes “D” connectors NEMA TS2 – 15 Pin Serial Connector port 1 CALTRANS/170/179/2070 (controllers) ATC All cabinets & controllers operate on a series of electrical inputs and outputs. Inputs/outputs as well as all the circuits and devices within the cabinet can be traced on the cabinet prints. 116 Electromechanical Controller The dials are equipped with keys that activate a switch. During installation, gears are installed to control the speed of rotation of each dial. As each key passes a microswitch, a motor is activated. 117 39  6/26/2024 Pre-NEMA Pre-NEMA This was the age when the first solid state electronic devices came into the public realm. Many manufacturers that were already doing electronic assembly for all types of electronic equipment began making traffic signal https://signalfan.tripod.com/control.htm controllers and cabinets. The problem that soon became evident to the end users was that there was no compatibility in equipment between manufacturers products. 118 NEMA TS1 National Electrical Manufacturers Association created the first traffic signal standards in 1976. The NEMA TS1 standard outlines the design, functionality, and performance requirements for traffic signal cabinets & controllers. NEMA defined: The cabinet style and 7 sizes by numbers (W x D x H): ◦ #1 - 16” x 12” x 24” (pedestal or pole mount) ◦ #2 - 20” x 14” x 32” (pedestal or pole mount) ◦ #3 - 24” x 15” x 40”or #4-24” x 16” x 46” (G) (ped, pole, or base mount) ◦ #5 - 30” x 16” x 48” (M) (pole or base mount) ◦ #6 - 44” x 24” x 52” (P) (base mount) ◦ #7 - 44” x 24” x 72” (R) (base mount) Controller functions in the “A”, ”B”, ”C” harnesses Conflict monitor functions and harnesses Load switches, flasher, and flash transfer relays Inductive loop detectors 119 NEMA TS2 NEMA TS2 National Electrical Manufacturers Association (Traffic Signal Controller Type 2) is an advanced standard for traffic signal controllers used in transportation and traffic management systems. It builds upon the features and capabilities of the NEMA TS1 standard, offering more advanced functionalities and communication options. 120 40  6/26/2024 Caltrans Type 170, New York 179 & 2070 170/179/2070 The robust and intelligent design of the 170/179/2070 cabinet series is perfect for any traffic control need. Meeting requirements set forth by Caltrans, New York, and the FHWA, these rugged cabinets offer easy access to interior assemblies. Original cabinet sizes: 332 (67” H x 24” W x 30” D) 336 (46” H x 24” W x 20” D) 121 Cabinet Type – ATCC & ATC The Advanced Transportation Controller Cabinet and the Advanced Transportation Controller are the newest cabinet / controller standards designed to provide an open architecture hardware & software platform to support a wide variety of ITS applications. Traffic Management systems ◦ Traffic Signals, Ramp Metering, CCTV's... Emergency management Freeway management ◦ Tolling, lane control, accident management... Public Transportation ◦ Light rail, busses... And the list goes on.... https://www.mccain-inc.com/products/cabinets/atc-cabinets/352i-atc-cabinet 122 Cabinet Components - Controller Controller - The controller is the brain of the traffic signal system. It https://www.cubic.com/transportation/intelligent-systems receives inputs from sensors https://www.econolite.com/solutions/controllers/cobalt-series/ and detectors in the field, processes the information, and generates output commands to control the operation of the traffic signals. The controller is responsible for timing the signal phases, coordinating signal sequences, and https://tcstraffic.com/traffic-controllers/ https://www.businesswire.com/ optimizing traffic flow. 123 41  6/26/2024 Cabinet Components – Conflict Monitor / MMU Signal Conflict Monitor / MMU: Conflict Monitor Units (CMU) – exist in TS-1 & Type 170 cabinets MMU’s – exist in TS-2 cabinets CMU’s (cabinet monitor units) exist in the ATCC cabinets The CMU/MMU serves two purposes: Signal monitor – which monitors the conditions of the signals, such as conflicting signals, lack of signals, or multiple signals on a single phase. Voltage monitor – which monitors operating voltages within the cabinet, such as the AC line voltage, controller operating voltages, and the DC voltages. If any of the above conditions occur, the monitor takes immediate action and places the signals in a flashing state until repairs can be made, or voltages return. A flashing signal is far safer for motorists to navigate rather than dangerous signal indications that cause confusion. 124 Cabinet Components – Conflict Monitor / MMU Signal Conflict Monitor / MMU / ATCC CMU: The monitor is the one safety device in the cabinet that signal techs and motorists rely on. So great care must be taken when working with one. Programming & settings must be correct!!! CMU/MMU/ATCC CMU manufacturers recommend that all monitors should be tested and recertified annually with CMU/MMU test equipment A strongly recommended practice is that, when you change out a monitor for testing, you record the model number and serial number of the old unit to be tested and the new monitor to be installed. GOOD RECORD KEEPING IS ESSENTIAL!!! 125 Traffic signal cabinets use detectors to input calls for vehicles, pedestrians, and emergency vehicle and railroad preemption. These detectors can be found in the detection rack. They include: Detection Loop amplifiers Magnetometers Devices Video detection processors Radar detectors AC & DC isolators EVP or RR preemption detection 126 42  6/26/2024 Cabinet Components – Power Supply Power Supply: The power supply provides electrical power to the traffic signal cabinet and its components. It typically includes transformers, circuit breakers, and power distribution equipment to ensure a stable and reliable power source. 127 Bus Interface Unit The roll of the BIU and how it interacts with Various Components: 1. Traffic Signal Controller: The BIU connects the traffic signal controller to the rest of the devices in the cabinet. 2. Traffic Detectors: The BIU interfaces with various traffic detectors, such as inductive loop detectors or video cameras, which provide input about the presence and movement of vehicles or pedestrians. 3. Terminal Facilities: The BIU connects to the load switches, which output voltage to the actual traffic lights. It controls the timing and sequencing of the lights based on the instructions received from the traffic signal controller. 4. MMU: The BIU communicates with the MMU so that the controller and the MMU may compare data. 5. Preemption Equipment: The BIU can also include preemption modules that allow other external devices, such as remote monitoring systems or emergency vehicle preemption systems. 6. Power Supply: The BIU receives power from the cabinet's power supply. 128 Serial Interface Unit A serial interface unit (SIU) is used in the ATC cabinets which is a device used to facilitate communication and data exchange between the controller and the other devices in the cabinet. The main functions of a serial interface unit in traffic signal cabinet include: Communication Protocols: The SIU supports specific communication protocols, such as NTCIP (National Transportation Communications for ITS Protocol) or other proprietary protocols, to enable seamless communication between the controller and the traffic signal equipment or ITS equipment in the cabinet, such as the input file which houses the detector devices, the Cabinet Monitor Unit (CMU), and the output file, which houses the high-density switch packs (HDSP). Inputs and Outputs: The SIU receives the detection inputs from the detectors in the cabinet and relays them to the controller. It also drives the output signals from the controller to the high-density switch packs. It communicates this through serial bus #1 (SB1) and serial bus #2 https://www.tacel.ca/products-services/ (SB2). 129 43  6/26/2024 Load Switches Load Switches / Load Packs : Load switches are interface devices between the controller and the field signals. The primary function of a load switch is to receive the 0/24 VDC input control signals from the controller and output a 120 VAC signal to the appropriate signal indications in the field. These devices are used in both NEMA (load switches) and Type 170 cabinets (“200” load Packs). If a load switch is not used, it is important to jumper pin #1 to pin #3 in the vacant load switch socket so that the monitor doesn’t see a fault on that channel. 130 High-density Switch Packs High-density switch packs: These high-density switch packs are only used in the ATCC cabinets They serve the same purpose as the traditional load switches, however... Due to the high-density design, there are two load switches on one card for a total of six outputs. These devices also double up as flasher units. 131 Flash Transfer Relays Flash relays are electrical switching devices used in traffic signal systems to control the flashing mode of the traffic signals. It is an electrical switch that is controlled by energizing or de-energizing the coil, thereby changing the state of the contacts through magnetism. What you are changing is either the RED or YELLOW load switch output or the flasher output to the signal indications in the field. These relays are used in both NEMA and Type 170 cabinets. Newer units may have an LED light to indicate an energized coil 132 44  6/26/2024 ATC Flash Transfer Relays Flash Transfer Relays: The next generation of flash transfer relays used in ATC cabinets. Much smaller design These relays are hermetically sealed and contain dry nitrogen gas to keep out: Moisture Insects Dirt Reduces sparking between the contacts Has an LED light to show the coil is energized 133 Flasher The flasher is the device that alternates two flashing, 120 VAC outputs to the signal indications. The rate of the flashing outputs per the MUTCD is 50 – 60 flashes per minute The upper flasher is strictly used in the ATC cabinets The lower “204” flasher is used in both NEMA and Type 170 cabinets. 134 Wire Labeling Ensure that all wires are labeled according to the phasing diagram in the signal plans or timing sheet. You will thank yourself in the long run with good cable labeling or color-coding tape. 135 45  6/26/2024 Cabinet Components – Back Panel, Power panel, Detection panel, Telemetry panel, Preemption panel Various panels are used in the traffic signal cabinet to control and interface with different components. The Back Panel: The back panel includes the field terminals, the load switch bay, the flasher(s), the FTR’s, and in some cases, the input/output terminals, and the power distribution components. 136 Cabinet Panels Power Panel: These panels include the power distribution equipment responsible for distributing power throughout the cabinet. Detection panels: These panels facilitate the detection inputs from the field and interface them into the controller. Telemetry panels: Facilitates communications between the controller and a T.O.C. or other system. Preemption Panel: Facilitates the EV & RR preemption inputs from the field and the controller. 137 Electrical Protection Main & Auxiliary Breakers: Circuit breakers are devices that protect electrical circuits and devices from overcurrent situations. Traffic signal cabinets have always had a 50 amp “main breaker.” Thanks to the onset of LED signals, main breakers are now rated at 30 amps. Cabinets also have auxiliary breakers, rated at 15 amps for cabinet equipment, such as the light, fan, and electrical outlets. Surge Protection Devices: These devices safeguard the components in the traffic signal cabinet from power surges or lightning strikes. They divert excess electrical energy to the ground, protecting sensitive electronic equipment from damage. These devices are used in all types of cabinets. 138 46