FACULTY OF ENGINEERING DEPARTMENT OF CIVIL AND STRUCTURAL ENGINEERING
KKKA 6424 INTELLIGENT URBAN TRAFFIC CONTROL SYSTEM Prof. Dr. Riza Atiq Abdullah O.K. Rahmat
TASK (3) (ARCHITECTURE) PREPARED BY:
1- HAIDER FARHAN P65405 2- MUSTAFA TALIB P60915 3- SAHAR ABD ALI P65295
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Introduction It is frequently observed in a rapidly growing city (e.g. in Malaysia) that traffic congestion and long queues at intersections occur during peak hours. This problem is mainly due to the poor coordination between adjacent traffic signal controls, resulting in inefficient progressive traffic flows (or commonly known as the unattainable ‘green wave effect’). Other problems are the inability of existing sensors to determine actual traffic demand and the conventional control methodology is unable to determine suitable green time split whenever the traffic demand exceeds capacity. In addition, suitable strategies to disperse congested traffic in major towns and cities cannot be formulated due to the unavailability of experienced traffic experts.
Traffic Management System The Traffic Management System (TMS) field is a primary subfield within the Intelligent Transportation System (ITS) domain. The ATMS view is a top-down management perspective that integrates technology primarily to improve the flow of vehicle traffic and improve safety. Realtime traffic data from cameras, speed sensors, etc. flows into a Transportation Management Center (TMC) where it is integrated and processed (e.g. for incident detection), and may result in actions taken (e.g. traffic routing, DMS messages) with the goal of improving traffic flow. The National ITS Architecture defines the following primary goals and metrics for ITS: • • • • • •
Increase transportation system efficiency, Enhance mobility, Improve safety, Reduce fuel consumption and environmental cost, Increase economic productivity, and Create an environment for an ITS market.
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TMS History In 1956, the National Interstate and Defense Highways Act initiated a 35year $114 billion program that designed and constructed the Interstate highway system. This hugely successful program was mostly complete by 1991, and the era of build-out was over. In the mid to late 1980s transportation officials from Federal and State governments, the private sector, and universities began a series of informal meetings discussing the future of transportation. This included meetings held by the California Department of Transportation (Caltrans) in October 1986 to discuss technology applied to future advanced highways. In June 1988 in Washington, DC, the group formalized its structure and chose the name Mobility 2000. In 1990, Mobility 2000 morphed into ITS America, the main ITS advocacy and policy group in the US. The initial name of ITS America was IVHS America and was changed in 1994 to reflect a broader intermodal perspective. The 1991 Intermodal Surface 3
Transportation Efficiency Act (ISTEA) was the first post-build-out transportation act. It initiated a new approach focused on efficiency, intelligence, and intermodalism. It had a primary goal of providing “the foundation for the nation to compete in the global economy”. This new mixture of infrastructure and technology was identified as an Intelligent Transportation System (ITS) and was the centerpiece of the 1991 ISTEA act. IT is loosely defined as “the application of computers, communications, and sensor technology to surface transportation”. Subsequent surface transportation bills have continued ITS funding and development. In 2005 the SAFETEA-LU (Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users) surface transportation spending bill was signed into law.
System Architect The systems architect establishes the basic structure of the computer system, defining the essential core design features and elements that provide the framework for all that follows, and are the hardest to change later. The systems architect provides definition of the users' vision for what the system needs to be and do, and the paths along which it must be able to evolve, and strives to maintain the integrity of that vision as it evolves during detailed design and implementation. A Systems Architect usually has the following responsibilities:
Overall design - the blueprints which provide the map High level planning for the development - overall steps for creation of the solution from the blueprints Integration constraints - rules and constraints for all components going into the solution Adherence to standards whenever possible - to maximize the future investment value and minimizing costs Customization for individual customer needs - understanding and recommending the best customization based upon the customer's needs (which include anticipation of their needs and explaining it in layman terms). 4
PROPOSED AUTOMATIC AND INTELLIGENT URBAN TRAFFICCONTROL (UTC) The optimization operation mentioned above could be carried out automatically if an intelligent UTC were installed on site. The proposed intelligent UTC in this documents based on fully distributed system because of the following reasons: • The system could be adopted easily into the existing system • Capital and operation costs are cheaper than that of centralized system • It could be expanded to almost unlimited expansion In contrast, most of the existing urban traffic controls are base centralized control. In a centralized control system, all timings are calculated by a central computer. The local controller would only implement the timing once it is received from the central computer. Usually the system would consider the traffic in terms of smoothed flow profiles; this makes the system slow in responding to rapidly changing traffic demands, such as during morning peak traffic growth period.
LOGICAL ARCHITECTURE The Logical Architecture defines what has to be done to support the services that are required by the user. It defines the processes that perform ITS functions and the information or dataflow that are shared between these processes. The Logical Architecture has also been called an "Essential Model" because it is not technology specific, nor does it dictate a particular implementation.
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Fig.1 Relative architectures Contrary to centralized control, the proposed system is based on a fully distributed system. In this system, all timings are calculated by the local signal controller. Coordination with adjacent intersections is possible if each controller can provide its neighbors with some information about its status, its future timing strategy and the time at which it expects the vehicles to leave its intersection before the controller starts optimizing the signalized intersection under its control. Since all timing calculations and co-ordinations are carried out at the local level, the distributed control is able to respond almost immediately to sudden fluctuation in traffic flows.
Fig.2 Distributed control architecture
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PHYSICAL ARCHITECTURE Physically the system consists of three basic components, namely the sensor (either inductive loops, smart camera or infra red system) for collecting traffic data, the controller for controlling traffic flows at an individual intersection and coordinator for coordinating the timing of an individual controller with its neighbors. The Physical Architecture provides agencies with a physical representation (though not a detailed design) of the important ITS interfaces and major system components. It provides a high-level structure around the processes and data flows defined in the Logical Architecture. The principal elements in the Physical Architecture are the 23 subsystems and architecture flows that connect these subsystems and terminators into an overall structure. A physical architecture takes the processes identified in the logical architecture and assigns them to subsystems. In addition, the data flows (also from the logical architecture) are grouped together into architecture flows. These architecture flows and their communication requirements define the interfaces required between subsystems, which form the basis for much of the ongoing standards work in the ITS program. The Local Area Network (LAN) approach is proposed to link up all controllers as shown in Figure 23. Each computer or microprocessor at the traffic light controllers given an IP (Internet Protocol) address. Each computer will share traffic data and timing with its neighbors for coordination purposes. In case where proactive control is required such as giving priority to an emergency vehicle, the computer at the control room will override the timing at each intersection with pre-determined timing that gives priority flows for an intended route.
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Fig. 3 Local Area Network For Network Of Traffic Controllers
SENSOR Sensor is a crucial element in an intelligent traffic control. The most common sensor is inductive loop. It is very common in vehicle actuated system to detect vehicle presence . It is also very common in an urban traffic control system to count them number or to measure headway of approaching vehicles. However, the main drawback of the inductive loop is its failure to measure queue length accurately. Another type of sensor is video detection system. This system is very flexible and able to carry out traffic count and measure queue length accurately. The price of commercial video detection system is very high as compared to inductive loop system. However a local institution has developed a low cost video detection system with the same capability as the commercial system. Figure 4.5 shows the video detection system currently used.
What is the difference between physical & logical architecture? The logical architecture is a more detailed structure defines what has to be done to support the user services. It defines the processes that perform functions and the information or data flows that are shared between these 8
processes. Logical architecture do not include physical server names or addresses. They do include any business services, application names and details, and other relevant information for development purposes. A physical architecture has all major components and entities identified within specific physical servers and locations or specific software services, objects, or solutions. Include all known details such as operating systems, version numbers, and even patches that are relevant. Any physical constraints or limitations should also be identified within the server components, data flows, or connections. This design usually precludes or may be included and extended by the final implementation team into an implementation design. 1-Overall
Diagram
Fig.4 Overall interior context diagram 9
2-traffic light system INTRODUCTION: ODERN traffic signal controls use highly capable Microprocessor based algorithms to control vehicle movements through intersections. However, the infrastructure that provides the interface between the controller cabinet, which houses the traffic controller, and the signals and sensors continues to use technologies developed as early as 1912. These dated technologies limit intersection communication capabilities, thus resulting in construction practices that are costly to install, maintain and upgrade. The goal of this research is to investigate the suitability and advantages for safety and access of applying modern distributed control practices to controlling signal lights for not only vehicles, but also pedestrians who \ are often overlooked in the design of intersection control. Additionally, research on enabling technologies will improve service for vehicles and pedestrians. Current practices treat all vehicles the same regardless of stopping and acceleration capabilities. Pedestrians too are treated as if they have equal mobility, agility, and cognitive abilities. With current traffic controls there is little opportunity to tune traffic controller operations based upon individual user needs.
Fig.5 Architecture of traffic light system 10
Fig.6 Diagram of the distributed traffic system
System Architecture For our tests, only the pedestrian signal and call buttons were implemented with smart signal design leaving the traffic lights under conventional traffic control operations. Fig. is a block diagram of the distributed traffic system architecture that was built and tested for this investigation. It consists of two independent Ethernet networks: one to provide communications with the traffic controller and one network for the real-time control of the distributed smart signals. The bridge node that interfaces with the traffic controller uses the National Transportation Communications ITS Protocol (NTCIP).[2] Also attached to the NTCIP network are two Windows based computers for simulation and configuration. The Traffic Operations computer generates messages to alter traffic signal timing representative of control from a traffic operations center. This computer was also used to implement preemption and setup the timing plans in the Traffic controller 11
Video detection system for traffic Light sensor The point based inductive loop is widely used in conventional traffic light sensors. The sensor is used either to detect the presence of vehicles or : to measure the gap or headway of the arriving vehicle in the vehicleactuated system or to count the traffic volume and to determine the queue length in a coordinated adaptive system. In a more sophisticated system, the sensor is also used to detect any traffic incident. However, the rising cost of installing the loops and disruption of traffic flows during installation or maintenance has resulted in the video detection system becoming more attractive. In addition, the cost of equipment for the video detection system has reduced substantially in the past l0 years. This paper describes the utilization of a video camera and image processing to detect the presence of vehicles, to count the volume of approaching traffic, to measure queue length and to detect traffic incidents at the approach road of a signalized intersection. Neural networks were used to detect the presence of the vehicles, to detect the traffic incident and to measure the queue length by identifying whether the road surface was occupied by vehicles and whether these vehicles were moving or stationary for a specified duration of time. The number of arriving vehicles was counted by observing the fluctuation of the selected pixels values in the middle of the traffic lane. A single camera which was developed in this study is able to capture the above mentioned parameters simultaneously from a multilane road approach
3-Smart Surveillance System 1. Introduction CCTV camera refers to Closed Circuit Television camera which is a video camera used to transmit the signal from a particular place to another. The images can be displayed on monitors and recorded for reference as well. It is widely employed as a surveillance system to monitor and keep track of happenings at places requiring monitoring traffic. Smart Video Surveillance is the use of computer vision and pattern recognition technologies to analyze information from situated sensors. Smart Cameras are becoming more popular in Intelligent 12
Surveillance Systems area. Smart cameras are cameras that can perform tasks far beyond simply taking photos and recording videos. Thanks to the purposely built-in intelligent image processing and pattern recognition algorithms, smart cameras can detect motion, measure objects, read vehicle number plates, and even recognize human behaviors. Currently, the majority of CCTV systems use analogue techniques for image distribution and storage. Conventional CCTV cameras generally use a digital charge coupled device (CCD) to capture images. The digital image is then converted into an analogue composite video signal, which is connected to the CCTV matrix, monitors and recording equipment, generally via coaxial cables.
Architecture of the Smart Camera
Fig. 7 smart camera architecture For traffic surveillance the entire smart camera is packed into a single cabinet which is typically mounted in tunnels and aside highways. The electrical power is either supplied by a power socket or by solar panels. 13
Thus, our smart camera is exposed to harsh environmental influences such as rapid changes in temperature and humidity as well as wind and rain. It must be implemented as an embedded system with tight operating constraints such as size, power consumption and temperature range. The smart camera is divided into three major parts: (i) the video sensor, (ii) the processing unit, and (iii) the communication unit.
Fig. 8: System architecture of the smart camera. 5.1 Video Sensor The video sensor represents the first stage in the smart camera’s overall data flow. The sensor captures incoming light and transforms it into electrical signals that can be transferred to the processing unit. A CMOS sensor best fulfills the requirements for a video sensor. These sensors feature a high dynamics due to their logarithmic characteristics and provide on-chip ADCs and amplifiers. 5.2 Processing Unit The second stage in the overall data flow is the processing unit. Due to the high-performance on-board image and video processing the requirements on the computing performance are very high. A rough estimation results in 10 GIPS computing performance. These performance requirements together with the various constraints of the embedded system solution are fulfilled with digital signal processors (DSP). 5.3 Communication Unit The final stage of the overall data flow in our smart camera represents the communication unit. The processing unit 14
transfers the data to the processing unit via a generic interface. This interface eases the implementation of the different network connections such as Ethernet, wireless LAN and GSM/GPRS.
The Single Stopped Vehicle (SSV) algorithm: The core of the IDS is the Single Stopped Vehicle (SSV) algorithm. Its primary objective is to detect stopped vehicles in high-speed, freeflowing traffic - a situation in which accidents tend to be most serious. When the first outstation detects a vehicle, it sends a message containing relevant vehicle data to the next downstream outstation. This next outstation will expect the vehicle to arrive within a certain time window. If it does, the outstation will inform the following one and so on. If it does not, it is likely that the vehicle has stopped between the two outstations and an alarm is raised. This is a simplification of the actual processing, which needs to keep a virtual map of all vehicles transiting each outstation pair. The IDS is able to detect and track vehicles straddling lanes and changing lanes between outstations. Alarms: Alarms are associated with the carriageway, the outstation and the lane number and, where applicable, provide the data for the relevant vehicle.
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Single Stopped Vehicle (SSV) This alarm is raised when a vehicle which was detected by an upstream outstation fails to be detected by the current one. The implication is that the vehicle has stopped somewhere between the two sites, either on the running lanes or the shoulder. Extra Vehicle This alarm is raised when an unrecognized vehicle is detected at a site, i.e. the vehicle was not detected by the previous outstation. This would normally be a previously stopped vehicle rejoining the traffic. Slow Vehicle This alarm indicates a vehicle was detected at a speed significantly below the current average speed of other vehicles on the highway. This is in itself a dangerous condition and may frequently indicate the vehicle is about to stop. Reverse Vehicle Any vehicle moving in the wrong direction on a highway is a hazard and an alarm is generated immediately. Slow Traffic This indicates the average speed of the vehicles has fallen below a predefined threshold at the site. The cause will usually be congestion. This will also happen upstream from an incident, which case it will probably be followed shortly by a Queued Traffic alarm. Queued Traffic A Queued Traffic alarm is raised to indicate traffic on that lane is showing shock-wave or start/stop behavior. This is usually due either to excessive congestion or a downstream incident. 16
Traffic information: Traffic information messages provide data collected over configurable time periods: • Traffic flow in vehicles per hour (on this lane) over the last time period. • Average vehicle speed over the last time period. • Presence of vehicles on the shoulder or in an ERA. • Currently active alarms. This includes the number of active SSVs for that lane, Slow Traffic and Queued Traffic indications. • Traffic count, in vehicles, over the last time period. For added flexibility, two data collection intervals are defined - one for the traffic count information and one for the flow, speed and alarm status information. Vehicle records: Every time a vehicle crosses a loop site, a record is generated including such information as: • Carriageway, lane and direction • Vehicle length and speed • Date and time of the occurrence and site occupancy time Other data may easily be obtained from this information, such as the headway between consecutive vehicles. Traffic information message processing: This provides a real-time picture of the highway conditions such as average speed and vehicle count. This can be used to warn of congestion, and support decisions, for example, to open a shoulder to traffic. Vehicle processing: Although the vehicle records are strictly a by-product of the incident detection processing, they provide significant opportunities in longerterm traffic management. These include:
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• Reconstitution of the highway scenario immediately prior to an accident, for legal support (Idris is accurate enough for speed enforcement) • Monitoring of traffic volumes and speeds at any level of detail (seasonal, weekly, daily, hourly, etc.) for future highway expansion planning. • Monitoring of traffic patterns (lane changes, speed variations) to support traffic management strategies both for day-to-day congestion management and scheduling of maintenance procedures. • Analysis of motorists' behavior in diverse situations (free flow, moderate congestion, congestion and as a shock-wave of an incident propagates back along the highway). • Vehicle records can be used real-time, when maximum information is needed at the Control Centre, or, once stored in a database, can be analyzed at leisure by even the most time-consuming algorithms.
4-VMS A variable electronic or dynamic message sign, often abbreviated VMS, CMS, or DMS, and in the UK known as a matrix sign,[2] is an electronic traffic sign often used on roadways to give travelers information about special events. Such signs warn of traffic congestion, accidents, incidents, roadwork zones, or speed limits on a specific highway segment. In urban areas, VMS are used within parking guidance and information systems to guide drivers to available car parking spaces. They may also ask vehicles to take alternative routes, limit travel speed, warn of duration and location of the incidents or just inform of the traffic conditions. A complete message on a panel generally includes a problem statement indicating incident, roadwork, stalled vehicle etc.; a location statement indicating where the incident is located; an effect statement indicating lane closure, delay, etc. and an action statement giving suggestion what to do traffic conditions ahead. These signs are also used for AMBER Alert and Silver Alert messages. 18
On the interchange of I-5 and SR 120 in San Joaquin County, California, an automated visibility and speed warning system was installed in 1996 to warn traffic of reduced visibility due to fog (where Tule fog is a common problem in the winter), and of slow or stopped traffic. VMS es were deployed at least as early as the 1960s. The current VMS systems are largely deployed on freeways or trunk highways.
Typical messages provide the following information: • • • • • • • • • •
Crashes, including vehicle spin-out or rollover Stalls affecting normal flow in a lane or on shoulders Non-recurring congestion, often a residual effect of cleared crash Closures of an entire road , e.g. over a mountain pass in winter. Downstream exit ramp closures Debris on roadway Vehicle fires Short-term maintenance or construction lasting less than three days Pavement failure alerts AMBER Alerts and weather warnings via the warning infrastructure of NOAA Weather Radio's SAME system • Travel times • Variable speed limits
The information comes from a variety of traffic monitoring and surveillance systems. It is expected that by providing real-time information on special events on the oncoming road, VMS can improve vehicles' route selection, reduce travel time, mitigate the severity and duration of incidents and improve the performance of the transportation network.
Fig. 9: variable massage signs 19
APPLICATIONS OF CMSs Permanently mounted CMSs are used primarily for the following applications: • Non-recurrent problems – Caused by random, unpredictable incidents such as crashes, stalled vehicles , spilled loads; or caused by temporary, preplanned activities such as construction , maintenance, or utility operations. • Environmental problems – Caused by acts of nature such as fog, floods, ice, snow, etc. • Special event traffic problems – Problems associated with special events (e.g., ballgames, parades, etc.). • Special operational problems – Operational features such as high occupancy, reversible, exclusive or contra flow lanes and certain design features such as drawbridges, tunnels, Ferry services. A limited number of agencies are also using CMSs for: • Recurrent problems – Caused by daily peak period traffic demand exceeding freeway capacities. In some cases, limits-of-congestion messages are displayed; in other cases, •
time messages are displayed.
Our suggestion is including adding one of variable electronic sign(VMS) on sungai besi highway because the driver high speed in this road and there is more accident in this area the VMS make helpless to reduce the speed especially motorcyclist.
Fig.10: variable massage sign
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Logical architecture of (VMS)
Fig. 11: logical architecture for VMS
Features: •
Wireless or wired network connectivity
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Power over Ethernet driven
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Enterprise-grade security support
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2D image support
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Wireless 802.11i support
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Simple design, faster time-to-market
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Applications: Freeway signs and traffic control
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Outdoor displays
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Stadium & arenas
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Displays outside malls/restaruants 21
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5-COMMUNICATION A good communication system is very crucial in an urban traffic control for the following purposes: • Synchronization of controller timer at each intersection for offset implementation. • Exchange of traffic data between controllers. • Malfunction reporting from each controller to the control room. • Incident reporting to the control room. • Use of the smart camera for surveillance purpose. • Data compilation at the control room would be used for the benefit of road users and research purposes.
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Fig. 12: smart camera Laying copper or fiber optic cable for this purpose is relatively very expensive and involves road digging. Renting existing commercial telecommunication cable also involves high operating cost. A wireless communication system is an alternative option to avoid high initial and running cost. Another alternatives using power cable plug Ethernet. This is actually a simple device that enables electricity cable to become LAN cable at the same time. This option will reduce communication cost tremendously as it will use existing power supply cable as the communication line with reasonable bandwidth.
System Communications Countdown timing and walk/wait state information are polled from the traffic controller by the bridge SNMP controller and are translated and rebroadcast to the PnP network controller that distributes this information to the smart signals and detectors. The service request information from the smart pedestrian call button uses the same route, but transmits minimal information which is translated by the SNMP bridge controller before reaching the traffic controller. In this implementation, the bridge node consists of two microprocessors, a SNMP translator and a PnP processor, operating in a master-slave configuration bridging the two Ethernet networks. Network communications with the traffic controller 23
use SNMP employing a point-to-point User Datagram Protocol (UDP) transport layer. All other devices use standard network Transmission Control Protocol (TCP) and UDP broadcast communications where each network node uses dynamic host configuration protocol (DHCP) for a unique local internet protocol (IP) address allocation. The two networks can be replaced with a common network hub or switch. However, they are shown as two independent networks in Fig. 2 to give emphasis to the use of Ethernet over power line (EoP). Every smart signal and detector as well as the translator and bridge processors operate as a network node.
6-Estimated cost Cost Solution Low cost solutions are the second output of this study, ranging from setting the optimum timing manually to an intelligent system with communication system. The intelligent system is based on distributed control system using microprocessors whereas the communication system is based on wireless system or system using power cable as the communication medium to minimize cost. INSTALLATION Installation is a very important part as it directly affects the cost and also the durability of the items installed. For every intersection, many items are needed to be installed. They comprise of four video cameras, an industrial PC, an image grabbing card, a multiplexer and support equipment such as video recorder and uninterrupted power supply which were placed beside the traffic light controller. Below is Figure 13 showing the camera as a sensor. Figure 5.2 shows the casing to contain the CPU. Figure 14 shows the existing steel pole that can be maximized for installation of cameras. Figure 13 Camera Figure 14 Computer for Image Processing and Traffic Light Controller Figure 15 Existing Pole At One Of The Intersection
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Fig. 13: Camera
Fig. 14: Computer for Image Processing and Traffic Light Controller
Fig. 15: Existing Pole At One Of The Intersecting 25
EXISTING SITUATION Most of the existing traffic signals controllers on the arterial roads under JKRjurisdiction is either operating on multi plan or vehicle actuated systems. While Multiplan system operates on a fixed time basis, the vehicle actuated system operates invariable timing based on the traffic demand. Although the vehicle actuated system responds almost immediately to the traffic demand, its behavior is unpredictable and thus difficult to coordinate between neighboring intersections. For the purpose of progressive flows where the coordination between neighboring intersections becomes crucial, multi plan fixed time system is much easier to handle. Most vehicle actuated system controllers have multi plan fixed time capability as a backup plan during inductive loops failure. In such cases, the multi plan fixed time system could be activated by disabling the vehicle actuated system. If the controller is dedicated for vehicle actuated system, then the authority has to replace the controller with a new one. Suggestions: Road traffic is currently the most important and flexible means of transportation in most countries. road freight transportation represents about 73% of the inland freight transportation market. The largest share of passenger transportation, around 85%, is carried by road . However, the current status of road traffic in many countries is extremely unpleasant. Road traffic is dangerous, expensive and has a high pollution rate. Road congestion is costing the EU-27 about 1% of itsGDP. Accidents injure or kill thousands of people every year. Traffic congestion in many big cities has gone almost out of control. Environmental damage is another issue. CO2 emissions from transportation in general and road transportation in particular have been rising faster than emissions from all other major sectors of the economy. Basically two approaches can be applied in order to solve or at least minimize these transportation problems. 1- ) The most straightforward solution is to build more infrastructure, such as bridges, roads and viaducts, in order to increase capacity. This solution is no doubt useful, especially for decreasing congestion, but it is 26
not sufficient. Constructing new road infrastructure is limited due to environmental, social and financial constraints. 2- )With difficulties of building more infrastructure and the aforementioned transportation problems, an approach in which already existing road capacity is better used is welcome. This second approach to traffic related problems is to control traffic by deploying Road Traffic Management Systems (RTMS), which contribute to efficiency as well as safety and environmental improvements. This is done by applying intelligence to the current infrastructure, switching from static to more dynamic road traffic control. There are many issues in designing and deploying RTMS. As a sociotechnical system, the organizational and regulatory policies, rules, processes and constraints have to be taken into consideration. These decisions have to be documented in what is called a domain architecture in this article. In addition to the policy decisions, the technical side of these systems is also challenging. Specific constraints such as interoperability with existing systems and the close relationship with the Environment makes the development effort extremely difficult. Besides, due to the high level of investments needed, these systems have to be flexible to be changed whenever new policies are to be implemented. The proposed solution in literature to build these large software systems is to base the design and development in an architecture [7], [8]. Future systems’ maintenance and evolution are facilitated when the architecture is clear for all stakeholders [9]. Basically, architecture refers to the organization of the system, such as its components, sub-systems, interfaces, and how these elements collaborate and are composed to form the system [10]. Only relevant decisions are important at this level, i.e., those that have a high impact on cost, reliability, maintainability, performance and resilience of the future system. The following is a summary of the user service requirements most pertinent to traffic signal control functions: The traffic control user service is designed to: ¨ Optimize traffic flow ¨ Provide traffic surveillance ¨ Provide ramp metering ¨ Provide the ability to give priority to certain types of vehicles 27
¨ Provide device control capabilities ¨ Provide information to other functions The incident management user service is designed to: ¨ Identify scheduled/planned incidents (e.g., construction activity) ¨ Detect incidents ¨ Formulate response actions ¨ Support coordinated implementation of response actions ¨ Support initialization of response actions ¨ Predict hazardous conditions The highway-rail intersection user service is designed to: ¨ Control highway and rail traffic in at-grade highway-rail intersections(HRIs) ¨ Coordinate highway and rail management functions ¨ Manage traffic in the intersection at all HRIs with active railroad warning systems ¨ Provide advanced warning of closures ¨ Provide automatic collision notification at HRIs with active railroad warning systems .Under this approach for this step, agencies should select those user services and user service requirements that are most relevant toward meeting the current and future needs previously identified. Those user services and user service requirements that remain in the preferred solution can be carried further into the next step of project development.
RECOMMENDATIONS Initial and maintenance works to optimize existing traffic controllers consume a great deal of time and energy. If this operation can be automated intelligently, the traffic flows could be optimized in real time automatically. For this reason, the study team Recommends that: • Upgrade the existing controllers to controllers with microprocessors • Install advanced sensors • Install communication system to facilitate data exchanges between traffic controllers which are necessary in optimizing traffic flows. 28