Alan Perrott, Tyco Fire & Integrated Solutions (UK) Ltd, looks at trends in CCTV technology for traffic surveillance applications
Typical IP surveillance system, showing operators in a central control room monitoring live and recorded video from several distributed sites and wireless cameras over the internet or a private Wide Area Network
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As our roads and other public transport routes become more congested, there is a growing need to monitor the transport network and manage demand and congestion more effectively. In addition, modern society's need for increased security and law enforcement has placed a greater burden on road operators. These requirements have led to the proliferation of cameras on our road networks. This mirrors the ever-increasing use of CCTV cameras for public area surveillance in town centres, shopping malls, airports and indeed anywhere and everywhere that there is a risk of crime or litigation. While roads operators and traffic management agencies also have to contend with our insatiable appetite for security and wellbeing, the operating environment and the specialised surveillance requirements for traffic management mean that traffic surveillance is a special case which presents its own particular challenges and requires specialist solutions.
4 per cent of the vehicles on UK roads at any one time are listed in the Police National Computer (PNC) database as being 'of interest'. Roadside cameras in conjunction with an effective Licence Plate Recognition/Automatic Number Plate Recognition (LPR/ANPR) system provide a valuable tool with which to monitor the movements of these vehicles and to help police intercept the drivers if required. The UK police's ANPR Strategy Paper 'Denying Criminals the Use of the Roads' (UK ACPO ANPR Steering Group, March 2005) makes it clear that LPR/ANPR and the wider concept of vehicle intelligence is an increasingly powerful - and cost-effective - policing tool.
However, the primary purpose of traffic surveillance cameras is to monitor and manage the road network. The main routes and intersections are often covered by CCTV cameras, with operators in central control rooms viewing the images from these cameras on a large video wall. This is clearly neither the most effective nor the most efficient way to monitor a large number of cameras. Technology is evolving to help automate this process, with a number of specialist manufacturers providing Automatic Incident Detection (AID) tools to automatically detect and report incidents such as queuing traffic, stopped vehicles and debris on the road. The motivating factor is that rapid detection of stopped vehicles and other traffic incidents speeds up intervention, improves traffic flow and potentially saves lives. Similar technology is being used for automatic traffic data analysis, gathering statistics such as traffic volume, average speed, headway, gap time, vehicle occupancy and vehicle classification. In urban areas, CCTV cameras are also used for other tasks such as intersection control and management, car park monitoring, and enforcement of traffic and parking regulations. CCTV cameras are commonly used at busy road intersections, either as a manual surveillance tool to monitor traffic flow, or with automatic video analytics technology as an alternative to induction loops and other detection technologies. In public car parks cameras are used to protect vehicles and their drivers, and to monitor the general use of the car park. Another major use of traffic surveillance cameras is to enforce traffic regulations. Cameras are frequently used to help detect and gather evidence of bus lane violations, illegal turns, illegal parking and other traffic offences. While technology exists to automate much of this, the legislation in most countries still requires enforcement to be a manual task.
The evolution from analogue to IP CCTV has many benefits for traffic surveillance. Once the video image has been digitised, it can be transmitted over any distance using any standard network transmission medium, and can be stored and retrieved all without any change in quality of the originally encoded video image. This makes video surveillance over wide areas with remote monitoring both cost-effective and practical. Rather than being dependent on a dedicated - and expensive - communications infrastructure, video data can now be transmitted at a much lower rate over multi-service networks along with other data. Similarly, video data can be stored and managed along with data from other applications to provide what is known in IT circles as Network Convergence. The use of a standard multi-service network reduces cabling costs, while the option of IEEE 802.3af Power over Ethernet (PoE) with most IP cameras removes the need for separate power cables to the camera. Camera control signals for pan, tilt, zoom and so on can also be transmitted over the network, so instead of three specialised cables to each camera for video, power and camera control we now have a single network cable.
Image quality is one of the most important features of any camera. This is especially true in traffic surveillance applications where lives are at risk. The traditional CCTV camera uses interlacing techniques originally developed for analogue TV monitor displays, made up of visible horizontal lines across a standard TV screen. Interlacing divides the display into two fields consisting of odd and even lines, and then alternately refreshes these fields. This delay results in a blurred image, particularly in traffic applications where there may be a lot of high-speed motion in the scene. Consequently, most traffic applications use a 2CIF image which effectively discards one of the fields and reduces the image resolution by half. An IP camera, on the other hand, uses progressive scan technology to capture the whole image at one time. This eliminates the delay and the resultant motion-blur between interlaced fields, and produces a better-quality image.
Video analytics is another area where traffic surveillance can benefit from research and development in other areas. Traditional video surveillance is a repetitive, time-consuming manual task that is often reliant on an operator spotting a momentary incident occurring on one of dozens of monitors. Using computer technology to detect traffic incidents and the behaviour that precedes them makes it possible not only to automatically detect when incidents have occurred but also to predict - and ultimately prevent - these incidents. While early video analytics systems were server-based with each camera routed back to a central analytics server, the advent of IP video and video encoders has led to edge-based architectures where the analysis is performed in a DSP on the video encoder or camera. This distributed architecture has the advantage that high-resolution video does not necessarily have to be transmitted to a central server for processing.
1028 Cisco and 62 IBM are already making significant strides into what they call 'physical security', and they will also be targeting the traffic surveillance market. While this network convergence has advantages, it will bring the traffic surveillance infrastructure under the auspices of the IT manager.
The digital age promises some exciting developments in the area of traffic surveillance: a more flexible communications infrastructure; reduced cabling and storage costs; better image quality; and improved video analytics tools. However, it will also present a lot of challenges, so hang on - it's going to be a bumpy ride.RSS
Alan Perrott,
As our roads and other public transport routes become more congested, there is a growing need to monitor the transport network and manage demand and congestion more effectively. In addition, modern society's need for increased security and law enforcement has placed a greater burden on road operators. These requirements have led to the proliferation of cameras on our road networks. This mirrors the ever-increasing use of CCTV cameras for public area surveillance in town centres, shopping malls, airports and indeed anywhere and everywhere that there is a risk of crime or litigation. While roads operators and traffic management agencies also have to contend with our insatiable appetite for security and wellbeing, the operating environment and the specialised surveillance requirements for traffic management mean that traffic surveillance is a special case which presents its own particular challenges and requires specialist solutions.
Traffic surveillance
Security remains one of the main uses of traffic surveillance cameras. Many of the vehicles on the road are of interest to the police - not necessarily in relation to serious crimes but to more minor offences such as unpaid insurance, vehicle excise or penalty notices. Recent figures from the UK, for example, indicate that up to4 per cent of the vehicles on UK roads at any one time are listed in the Police National Computer (PNC) database as being 'of interest'. Roadside cameras in conjunction with an effective Licence Plate Recognition/Automatic Number Plate Recognition (LPR/ANPR) system provide a valuable tool with which to monitor the movements of these vehicles and to help police intercept the drivers if required. The UK police's ANPR Strategy Paper 'Denying Criminals the Use of the Roads' (UK ACPO ANPR Steering Group, March 2005) makes it clear that LPR/ANPR and the wider concept of vehicle intelligence is an increasingly powerful - and cost-effective - policing tool.
However, the primary purpose of traffic surveillance cameras is to monitor and manage the road network. The main routes and intersections are often covered by CCTV cameras, with operators in central control rooms viewing the images from these cameras on a large video wall. This is clearly neither the most effective nor the most efficient way to monitor a large number of cameras. Technology is evolving to help automate this process, with a number of specialist manufacturers providing Automatic Incident Detection (AID) tools to automatically detect and report incidents such as queuing traffic, stopped vehicles and debris on the road. The motivating factor is that rapid detection of stopped vehicles and other traffic incidents speeds up intervention, improves traffic flow and potentially saves lives. Similar technology is being used for automatic traffic data analysis, gathering statistics such as traffic volume, average speed, headway, gap time, vehicle occupancy and vehicle classification. In urban areas, CCTV cameras are also used for other tasks such as intersection control and management, car park monitoring, and enforcement of traffic and parking regulations. CCTV cameras are commonly used at busy road intersections, either as a manual surveillance tool to monitor traffic flow, or with automatic video analytics technology as an alternative to induction loops and other detection technologies. In public car parks cameras are used to protect vehicles and their drivers, and to monitor the general use of the car park. Another major use of traffic surveillance cameras is to enforce traffic regulations. Cameras are frequently used to help detect and gather evidence of bus lane violations, illegal turns, illegal parking and other traffic offences. While technology exists to automate much of this, the legislation in most countries still requires enforcement to be a manual task.
Towards IP
The traditional traffic surveillance system consisted of a number of analogue cameras, with the video image from each camera routed back over a dedicated fibre-optic communications infrastructure to a central control room. The video inputs would be switched to one or more video monitors by a video matrix and the video images may be recorded on a VCR or DVR. However, over the last 10 years this traditional CCTV model has gradually been superseded by digital video and IP-based network transmission. While the analogue camera that so much has been invested in may remain for the time being, the 1V peak-to-peak video signal is now usually digitised at the roadside by a video encoder device using an industry-standard compression format. In newer systems, the camera sensor and encoder may be combined in the form of an IP camera. Either way, the resultant digital video signal can now be transmitted over a standard IP network, stored in standard IT storage systems and viewed by software applications on industry standard PCs, PDAs or even smart phones.The evolution from analogue to IP CCTV has many benefits for traffic surveillance. Once the video image has been digitised, it can be transmitted over any distance using any standard network transmission medium, and can be stored and retrieved all without any change in quality of the originally encoded video image. This makes video surveillance over wide areas with remote monitoring both cost-effective and practical. Rather than being dependent on a dedicated - and expensive - communications infrastructure, video data can now be transmitted at a much lower rate over multi-service networks along with other data. Similarly, video data can be stored and managed along with data from other applications to provide what is known in IT circles as Network Convergence. The use of a standard multi-service network reduces cabling costs, while the option of IEEE 802.3af Power over Ethernet (PoE) with most IP cameras removes the need for separate power cables to the camera. Camera control signals for pan, tilt, zoom and so on can also be transmitted over the network, so instead of three specialised cables to each camera for video, power and camera control we now have a single network cable.
Image quality is one of the most important features of any camera. This is especially true in traffic surveillance applications where lives are at risk. The traditional CCTV camera uses interlacing techniques originally developed for analogue TV monitor displays, made up of visible horizontal lines across a standard TV screen. Interlacing divides the display into two fields consisting of odd and even lines, and then alternately refreshes these fields. This delay results in a blurred image, particularly in traffic applications where there may be a lot of high-speed motion in the scene. Consequently, most traffic applications use a 2CIF image which effectively discards one of the fields and reduces the image resolution by half. An IP camera, on the other hand, uses progressive scan technology to capture the whole image at one time. This eliminates the delay and the resultant motion-blur between interlaced fields, and produces a better-quality image.
Technology trends
The move to IP video brings traffic surveillance technology in line with mainstream IT and video processing. As a result, traffic surveillance is able to take advantage of advances in technology in these areas - and there is a lot happening. The drive towards reliable wireless data transmission with ever-higher bandwidth brings huge benefit to traffic applications: wireless Mesh networks can be used in town centres as an alternative to traditional wired communications; 3G transmission is being used for rapid-deployment cameras that can be quickly set up to monitor temporary events and for remote viewing of fixed cameras. Megapixel cameras allow us to move beyond the restrictions of traditional NTSC/PAL specifications, with image resolutions of 1600x1200 or higher. And, as megapixel cameras provide much more detail than analogue CCTV cameras, it is possible to cover the same area with fewer cameras. At the same time, the increased definition makes it possible to digitally zoom and pan within the wider field of view - both for live and recorded images.Video analytics is another area where traffic surveillance can benefit from research and development in other areas. Traditional video surveillance is a repetitive, time-consuming manual task that is often reliant on an operator spotting a momentary incident occurring on one of dozens of monitors. Using computer technology to detect traffic incidents and the behaviour that precedes them makes it possible not only to automatically detect when incidents have occurred but also to predict - and ultimately prevent - these incidents. While early video analytics systems were server-based with each camera routed back to a central analytics server, the advent of IP video and video encoders has led to edge-based architectures where the analysis is performed in a DSP on the video encoder or camera. This distributed architecture has the advantage that high-resolution video does not necessarily have to be transmitted to a central server for processing.
The Future
While the digital age of CCTV brings real benefits to traffic surveillance, it also poses some significant challenges. As with any evolving technology standardisation will take a while to catch up, so in the meantime we will have to contend with a variety of competing standards. The change in focus from traditional engineering technology to IT systems means that a very different skillset is required to sell, install, manage and support these systems. This is already exposing a skills gap in these areas, leading to the inevitable migration of IT companies into the traffic management industry. Organizations likeThe digital age promises some exciting developments in the area of traffic surveillance: a more flexible communications infrastructure; reduced cabling and storage costs; better image quality; and improved video analytics tools. However, it will also present a lot of challenges, so hang on - it's going to be a bumpy ride.RSS
