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Home My WebLink AboutSS04 - Overview of Traffic Signal0 February 22, 2000 CITY COUNCIL STUDY SESSION ITEM NO. SS4 TO: Mayor and Members of the City Council FROM: Public Works Department SUBJECT: OVERVIEW OF TRAFFIC SIGNALS The City of Newport Beach has 71 traffic signals operated by the Public Works Department. A number of these are along the City boundary and the costs are shared with either the City of Costa Mesa or Orange County. Another 30 signals are operated by Caltrans along Coast Highway, Newport Boulevard, and the Bristol Street couplet. The City of Costa Mesa operates one signal. The City of Irvine operates eight signals along our common boundaries. We share in the cost of the operation of these signals. There are currently five new signals under design or construction by either the City or a developer, which will be operated by the City. • Signal Components The key components of a traffic signal are the controller assembly, the detectors, and the signal displays. The controller assembly includes a microprocessor similar to a personal computer. Staff programs the controller with various timing parameters such as minimum and maximum length of green, yellow, and all -red times, as well as pedestrian intervals. The controller assembly also includes a conflict monitor. As the name suggests, it monitors what the signal is doing, and the electrical power input. If it senses a power problem, or that two conflicting directions are getting a green light at the same time, it switches the signal to a flashing red mode for safety purposes. The great majority of signals in the City are traffic- actuated, meaning the controller device is activated by detectors on all approaches. This enables it to proportion green signal time according to traffic demand. The detectors are loops of wire in the pavement that sense the presence of a metallic object such as a car, truck, or motorcycle. Two of the signals now under design will use video cameras instead of wire loops to detect vehicles. In addition to these vehicular detectors, all of the signals have push buttons for pedestrians and most intersections also have push buttons for bicyclists to use. Detectors have a design life of approximately ten years and unfortunately they represent a significant portion of the maintenance costs of signals because they are frequently damaged by contractors and must be replaced when a roadway is resurfaced. SUBJECT: Overview of Traffic Signals . February 22, 2000 Page 2 Vehicular signal heads include green, yellow, and red lights which are usually twelve inches in diameter. Each turning or through movement has at least two signal heads that must be visible to the driver far enough from the intersection for them to respond appropriately. Historically incandescent bulbs have been used for the light source. Recently we began using Light Emitting Diodes (LED's) for the red indicators for their long life and low energy consumption. Traffic Signal Timing Traffic signal timing begins with setting various parameters for the individual intersection. Staff looks at historic traffic counts during the AM and PM peak hours, as well as mid -day. Based on these counts Staff determines the settings necessary to provide the most efficient operation of the signal. The key settings are the maximum length of time that a movement can have a green light, the length of the yellow light (which is a function of the speed of traffic), and how long the detectors hold the signal green after a car passes over them. Traffic Signal Coordination • Most cities and Caltrans coordinate signals along major streets to smooth traffic flow and reduce the amount of time motorists spend waiting at a red light. The Public Works Department's Traffic Signal Master Computer allows Staff to monitor and adjust the timing on approximately 60 of the 71 signalized intersections the City operates. This computer system coordinates some or all of the signals along Jamboree Road, Irvine Avenue, Superior Avenue, and Balboa Boulevard. Caltrans uses a different system to coordinate nearly all of their signals. We have joint coordination with Caltrans along Newport Boulevard between 28th Street and Via Lido. Additional timing parameters must be developed to provide the most efficient sequencing of lights along the roadway. Where there is a heavy movement in one direction during a certain time of day, the signals are set to give a preference to that direction. A number of factors such as varying volumes, intersection spacing, signal design, and the level of pedestrian activity can severely limit the ability to provide the level of coordination that every motorist would like to have. A number of years ago the Orange County Transportation Authority (OCTA) studied signal coordination in response to the large amount of interest in this topic generated by Measure M. They concluded that coordination would improve traffic flow by only 10 to 15 percent above that provided by signals that were traffic actuated. • iSUBJECT: Overview of Traffic Signals February 22, 2000 Page 3 Frequently Asked Questions /Complaints The attached document lists the most common questions and complaints staff receives from the public. Staff will make a presentation on the City's signals at the Study Session and will try to answer questions about specific intersections, or coordination of signals along the major streets in Newport Beach. Respectfully Submitted, C 029 PUBLIC WORKS DEPARTMENT Don Webb, Director By: .4A4�_41� • Richard Edmonston, P.E. Transportation and Development Services Manager Attachment 11 Frequently Asked Questions /Complaints of Traffic Signal Operations • 1. The traffic signal is not working right. 2. Why do I always get a red light at this location? 3. 1 have to wait too long for a green light. 4. Why do I sometimes stop at a coordinated signal? A number of operations may give the impression that a signal is not operating properly in addition to those times when there actually is an equipment malfunction. The most common answers to these questions and complaints are listed below: A. A pedestrian or bicyclist pushes the pedestrian button and crosses the street. Frequently a pedestrian needs more crossing time than the regular signal timing provided for vehicles alone. This causes delay to the motorist. Sometimes the pedestrian or bicyclist pushes the pedestrian button but crosses the street without waiting for the "Walk" light. The traffic signal must still provide time for a safe crossing. A pedestrian crossing a six -lane street such as Jamboree Road needs approximately 35 seconds. B. A pedestrian button is stuck or broken. This puts a pedestrian call (lasting up to • 35 seconds) in every cycle - 24 hours a day, 7 days a week, until it is repaired. C. The traffic signal loop or loops are inoperable due to age, pavement degradation, or damage from construction. This may cause intermittent or continuous problems until repaired. When a loop fails, it sends the controller a message that there are vehicles constantly waiting for a green light. The signal will hold a green light up to the maximum time on the controller that is serving this non- existent traffic. D. The signal is coordinated with adjacent locations and is holding green for through traffic that may be approaching the intersection. When signals are coordinated, they provide a priority for through traffic on the coordinated street. As a result, traffic on the side street or in a turn pocket will likely experience somewhat longer delays. E. A fire truck or ambulance has just passed through the intersection and preempted the normal sequence of the signal. This can cause the signal to skip certain movements until after the emergency vehicle has passed through or the pre- empt timing has completed its sequence. Coordinated signals may take up to ten minutes to re- establish coordination after being disrupted. CJ • F. Many drivers are not used to lagging left turns where the left turn green arrow comes up at the end of the green light for the through phase. They expect the left turn arrow at the beginning of the cycle. When it does not happen, they report it as a malfunction. G. The traffic signal controller is not responding correctly and is malfunctioning. While modern signal equipment is quite reliable, it can and does fail from time to time. H. When a signal is under coordination and there is light traffic on the side street or in the turn lanes, the signal will release traffic on the main street earlier than is necessary for the coodinated system. This will likely cause the driver to stop at the next signal. I. The traffic timing for a particular movement may be too short to provide the needed green light time to clear traffic. When this is the case, the timing may be adjusted or a study is made to determine other solutions such as adding an additional lane for that movement. • HOW DO WE KNOW WHEN A TRAFFIC SIGNAL IS MALFUNCTIONING? 1. Many signal malfunctions are monitored by the City Vehicle Management System (VMS) computer program. 2. The Police, Fire, Public Works and General Services Departments have vehicles in the City during the day and night. These Departments report malfunctions to either the Traffic Engineering Division or the Police Department. The City's contract maintenance company or Caltrans is then called to respond. 3. Monthly maintenance and field reviews are made by the City's maintenance company. Caltrans also performs monthly reviews of their equipment. 4. City Traffic Engineering staff are trained to look for malfunctions whenever they are in the field. •