Presentation on theme: "Presented by: Betsy Williams TransCore"— Presentation transcript:
1Presented by: Betsy Williams TransCore The Technology Side of the Sydney Coordinated Adaptive Traffic System (SCATS)I’m Betsy Williams, TransCore’s area manager in the Atlanta office.SCATS has been around long enough that I expect most of you have at least heard of it. I was asked to talk to you today about the technology side of SCATS, since we’re an ITS organization, not a planning crowd.I will give you a little bit of background on the system,Briefly describe the benefitsTell you about the objectives of the systemThen get into the technology requirements of detections, controllers, server hardware, and communications.Presented by:Betsy WilliamsTransCore
2SCATS BackgroundThe Roads and Traffic Authority of New South Wales (RTA)Developer and primary user of SCATSContinued innovation through user group involvementExtensive user baseEffective, mature, practical systemWorldwide - over 21,000 intersections under SCATS control in 71 installationsSCATS was originally developed by the RTA for use in Sydney, thus the name Sydney Coordinated Adaptive Traffic System. RTA continues to be the primary developer for the software, continually making improvements and innovations based on input from users in over 71 installations worldwide.Since SCATS initial deployment in the 1980s, it has grown to over 21,000 intersections in 71 installations worldwide.
3SCATS Worldwide System Installations DublinWaterfordGreshamPark CityMenlo ParkSunnyvaleRzeszowDetroitShenyangDelawareDurhamTehranMashhadCobb CoShijuazhuangChula VistaIsraelYanbuYichangTianjinShanghai, NingboSuzhou HangzhouPasco Co.DohaGuangzhouMexico CityTolucaHong KongDacca HanoiPattaya VietianneManilaCebuKuala LumpurSerembanSingaporeBruneiSandakanJakartaBandungThe majority of SCATS installations are in Australia, southeast Asia, and China. The number of US installations continues to grow.Suva FijiDarwinPerth Adelaide SydneyMelbourne& many other citiesPietermaritzburgConcepcionAuckland Wellington Christchurch + 11 cities
4SCATS US Installations The Road Commission of Oakland County Michigan was an early user, even when they had to use imported Australian controllers and install them upside down (just kidding). Now they use 170s at over 600 intersections.Cobb County’s SCATS installation in the Cumberland/Galleria area is now the 2nd largest in the US, with 74 intersections online.
5Benefits of SCATS Reduces need/effort for updating signal timing Accommodates traffic fluctuationsAllow special functions to be installed for event centersAssist maintenance of signals via monitoring featuresCollect volume counts for planning purposesAs expected, SCATS keeps up with changes in volume, whether it’s a temporary change or the result of growth or development, so the need for retiming is reduced.SCATS also accommodates unexpected traffic changes, such as early peaks, accidents, or special events. Special functions can also be programmed to handle traffic at event centers.A less well-known benefit is the robust monitoring capabilities of the system, especially for detectors. SCATS sends up a flag if a detector doesn’t place a call for a certain length of time, so the system thinks there’s an open circuit.
6Typical Adaptive vs. TOD Graph So… what does SCATS adaptive timing look like compared to a good time of day plan?This graph shows the cycle lengths of a time of day plan (the red line) compared to SCATS adaptive cycle lengths.You can see that the TOD plan went to a morning peak cycle length before it was really necessary, it wasn’t long enough for a few times, and it dropped back to a shorter cycle length too soon at the end of the day.The dark blue space between the necessary cycle length and the TOD cycle length can translate into delay for somebody at the intersection.
7SCATS Objectives Select cycle length, splits and offsets to achieve Minimum stops with light demandMinimum delay with normal demandMaximum throughput with heavy demandSCATS uses real-time data from detectors to optimize three parameters (cycle length, splits, and offsets) for the entire system.With light demand, SCATS minimizes stops.With normal demand, SCATS minimizes delay.With heavy demand, SCATS maximizes throughput.
8SCATS DetectionNow… we’re to the technology part.
9SCATS Detection Requirements YESStop barNOAdvancedUpstreamDownstreamMid-blockI think the most common misconception about SCATS is that it’s very detection intensive. In reality, the system requires only stop bar detection, not advanced detection, upstream detection, downstream detection, mid-block detection, retina scans, or anything else.
10SCATS Detector Requirements Presence detectionOptimal strategic SCATS detectors are 6 ft x 15 ft located at the stop line for all lanesDetectors can be longer or shorter if needed, however shorter is better than longerLocal actuation detectors may be used at minor intersections and can be varying in sizeThe detector technology can be loop detection, as is used in Oakland County, or it can be video detection, like Cobb County is using. The system simply needs presence detection.Optimally, detectors should be 6x15 and located 3 feet behind the stop bar, one detector per lane.If a detector is longer or shorter, the system can handle it, but shorter is better than longer. As I’ll explain in a minute, SCATS looks at the space between vehicles, so a long detector is less likely to calculate that space accurately.
11Typical Detector Layout This illustrates the typical detector layout: one detector per lane, right behind the stop bar.
12SCATS Detectors SCATS operates by looking at “space” between vehicles Eliminates vehicle length from equationGraph is linear with no double curvesHere’s a very simplistic description of the “space time” factor SCATS uses to determine traffic density.SCATS looks at how much time the detection zone is unoccupied. When there is a lot of “space time” traffic density is low, but when there isn’t much “space time” traffic density is high.Compare that to an algorithm that uses traffic volumes to determine density. Low volume could mean that there isn’t much traffic on the street, or it could mean that there’s so much traffic that nobody can move and the cars aren’t passing through the detection zone very often.LoopSpace Time (secs)
13SCATS EquipmentOn to the other hardware and communications
14SCATS Controllers SCATS uses 2070 controllers Eagle M-50 series 2070 Lite – no VME backplaneEagle and Econolite 2070s2070N – reuse of existing cabinetsEagle M-50 series170 E controllersSafeTran or McCain controllersI’d guess that the second most common misconception is that SCATS still requires Australian controllers. NOT SO!TransCore invested a lot in getting the SCATS controller software ported to the 170 controller, and now the system will run on both 170s and 2070s.I have to admit that I’m not very knowledgeable about controllers, but these are all controller models that SCATS is currently running on in various locations around the US.
15Hardware Requirements Server RequirementsMinimum 400 MHz Intel processor – 128M RAMWindows NT or 2000Laptop and Workstation RequirementsMinimum 400 MHz Intel processor – 128M RAMWindows NT, XP or 2000Dial-in access56K modemVPN accessAs far as the system server in the control center, it doesn’t take much horsepower to run SCATS. The centralized system constantly takes in data from each intersection and optimizes the cycle length, splits, and offsets, and send the operating instructions back to the controller.The server needs to use Windows NT or 2000, have a minimum 400 MHz Intel processor, and 128meg of RAM.The workstation, which can be a laptop, has the same requirements except it can also run Windows XP.Dial-in access only requires a 56K modem, or you can connect remotely by VPN access.
16CommunicationsLeased line, twisted pair copper, fiber optic, spread spectrum radio300 bps per controllerPoint-to-point communicationPoint-to-multipoint communicationEthernet/IP communicationsIf you’re used to high bandwidth ITS devices such as CCTV cameras, SCATS requires next to nothing. The thousands of intersections in Sydney use twisted pair copper communications for years.Each controller only requires 300 baud comm, so the comm can be leased line, twisted pair, spread spectrum radio, or fiber optics. Cobb County’s system is using county-owned fiber optic cable.We can use point to point communication, point to multipoint, or IP addressable ethernet comms.
17SCATS OperationI really hoped we’d be able to dial in to Cobb County’s system and show you some real-time operation…
18SCATS Modes Adaptive Mode Time-of-Day Mode Free Mode Master Free Mode Traffic adaptive coordination modeTime-of-Day ModeFixed-time coordination fallback modeFree ModeVehicle actuated operationMaster Free ModeVehicle actuated with SCATS calculated splitsFlashSo I’ll just have to describe some of this to you.In addition to operating in adaptive mode, SCATS can also run time of day plans. This is how the intersections will run if they lose communications with the central server.Free mode in SCATS is just like free with other systems: vehicle actuation drives all of the signal operations. This is how most intersections around here run in the middle of the night, unless detectors are malfunctioning, then… well, you know what happens. It stays red for you for a long time until you get so frustrated you run the light.Master free modeSCATS intersections go into flash just like other systems, if the conflict monitor is tripped or the controller dies or by manual operation.
19SCATS GUI Familiar Windows interface Real-time information Pull down menusReal-time informationI have a few slides of the SCATS graphic user interface. It’s a windows-based interface with pull down menus and real-time updates on the signal operation.We can see a lot about the system or an individual intersection at a glance.
20Active Time-Space Monitor One display that we use a lot is the active time-space monitor.You can set up corridors and watch the activity at every intersection along the corridor.The time-space monitor is pretty similar to most time space diagrams that traffic engineers are used to seeing, except that you don’t see the entire green band progressing down the road.
21ReportsSCATS has some nice reporting tools. This particular report shows the operation of a single intersection for a 24 hour period. You can see the amount of time each phase got throughout the day.
22These two graphs are a great illustration of the power of SCATS to adapt to unusual conditions. The graph on the bottom is typical operation at a signal near the mall on Sunday. The peak comes in around 10:00 a.m. and is steady, with a couple of blips between noon and 3:00.The graph on top is the previous weekend: Mother’s Day. Traffic picked up several hours earlier and had an unusual peak at about 8:00 when all those nice kids took their mothers to breakfast, and another big spike between 11 and 12 when the rest went out to lunch. The spike at 5:00 must be when the mothers went back to the mall to buy their own present.
23For additional information contact: Betsy Williams TransCore (770) or Travis White TransCore (801)
25Proven Performance Chula Vista, CA Menlo Park, CA Travel Time Reduced By Up To 15%Travel Speed Increased By Up To 18%Delay Reduced By Up To 43%Menlo Park, CAStops Reduced By Up To 24%Travel Time Reduced By Up To 28%Delay Reduced By Up To 44%
26Proven Performance Road Commission For Oakland County, Michigan Corridor Travel-Time Reduction Range 6.56% To 31.8%Average Travel-Time Improvement 7.8% For Peak Traffic During Peak PeriodsBroward County, FloridaStops Reduced By Up To 28%Travel Time Reduced By Up To 20%Delay Reduced By Up To 42%
27SCATS Functions - CYCLE LENGTH Automatically calculated to try to maintain Degree of Saturation between 80% and 90% on the lane with the highest DSLower and upper limits are user definable (20 secs to 190 secs)Can vary by up to 21 seconds per cycle – usually only 2 to 5 seconds
28SCATS Functions - SPLITS Varied automatically by up to 4% each cycle.Tries to maintain equal Degree of Saturation on competing approaches.Minimums are user definable.Maximums are limited by cycle length and minimum requirements of other phases.
29SCATS Functions - Linking Intersections can "marry" or "divorce " with each otherMarried intersections operate on a common cycle length (and offset plan)Intersections marry:when their CL's are within 10 sec orwhen one-way volume exceeds a configured threshold orwhen a “forced” / continuous “marriage” is requiredSS 1SS 2SS 3SYSTEM
30SCATS Functions – OFFSETS The best offsets are selected for the high flow movements.Preset offset plans automatically vary to compensate for varying cycle lengths.Directional bias based on measured flows.
31Intersection Display Currently activated detectors shown blue. Shown red if faulty
32Alarm DisplayAll operator actions and alarms can be sorted, filtered and printed