Since the 1978 reform, China’s economy has grown steadily at an average rate of 7-8% per annum, becoming the fastest growing major economy in the world with a nominal GDP of about US$5 trillion in 2009. The rapid expansion of the Chinese road network, also known as the National Trunk Highway System (NTHS) is driven by the country’s economic growth. China’s expansion strategy has led to increasing freight transport levels, demographic changes that saw the urbanization rate increase from 17.4% to 41.8% between 1978 and 2005, and a growing middle class resulting in car ownership to reach a projected total of 75 million vehicles by the end of 2010.
The Need for Intelligent Transportation Systems in China
The NTHS, which comprises Expressways, class 1, class 2 and class 3 highways, is expected to reach a total of 3 million kilometers by 2020*. The Expressway network, currently second only to the USA’s with 65,000 km, is expected to expand to 85,000 km by 2020. The current National Expressway Network Plan includes the development of seven highways radiating from Beijing, nine North to South Expressways and 18 East to West Expressways with an emphasis being put on linking cities with 200,000 and more inhabitants to serve a population of over one billion people across China.
With traffic congestion, such as the recent traffic jam on parts of the Beijing-Tibet expressway that stretched 100 km over nine days, becoming endemic, the Chinese authorities have invested heavily in the past few years in the development of Intelligent Transportation Systems (ITS) inviting domestic and international firms to design and implement ITS solutions to make roads safer for all users. In Q4-2009 alone, 1,063 ITS projects worth just over RMB $2bn (US$ 33m) were under way throughout the country including 384 in traffic light control systems, 238 in law enforcement, 238 check-points and 203 traffic surveillance projects.
Allied Vision Technologies (AVT) is currently involved in multiple ITS projects in five major metropolitan areas as a provider of machine vision cameras to system integrators in partnership with China Daheng, its well-established local distributor.
ITS at Work – City and Expressway Solutions
In China, unlike in Europe or North America, ITS solutions are planned in advance and are commonly integrated in the roadway during construction, eliminating the need for additional civil work, on-site reconfiguration and most importantly road closures or service interruptions. ITS in the city and on Expressways is commonly used in China for three main applications: intersection, check-point and traffic flow on highway.
Large intersections are monitored to detect several types of traffic violations depending on the local requirements including vehicle crossing during a red light, wrong use of lane (wrong turn) and license plate reading (LPR). Each installation includes four cameras, one on each side of the intersection, paired up with two LED lights on either side for night-time image capture. The equipment is positioned 20 meters from the traffic lights stop line aimed in the direction of traffic flow. A 2 Megapixel industrial camera, such as the Prosilica GC1600C model from AVT is used to track up to two lanes of traffic while a 5 Megapixel camera, such as the Prosilica GC2450C from AVT is preferred for three lanes. 16 mm focal length C-mount lenses are mounted on the cameras to provide a wide field of view and crisp image detail. Two ground-loop detectors are installed below the roadway surface. The detectors are positioned before and after the intersection stop line to detect vehicles and trigger the camera. To provide proof of red light violation images of the vehicle are captured before, during and while it is exiting the intersection. Installations are often networked to reduce hardware costs. Detected traffic violations are transmitted via fiber optics cable on a dedicated communications network to a remote police center where they are analyzed and stored. Police operators can manage the intersection remotely by setting up parameters for the front-end equipment via the software interface.
Installations for check-points on Expressways in China are automated traffic control systems that typically feature up to three 2 Megapixel color cameras and one LED light depending on the number of lanes that need monitoring. Check-points are used for law enforcement and traffic management. Police authorities use the check-points to detect suspicious vehicles passing through an area; this could include a car without a license plate or a stolen vehicle. Once a suspicious vehicle is detected an alarm is automatically raised to alert the local police authorities. Traffic management personnel on the other hand utilize the check-points to monitor traffic flow and measure the average speed of vehicles.
The Many Benefits of Machine Vision Cameras in ITS
Although traditional film and digital consumer cameras are common in traffic imaging, the industry is beginning to recognize the considerable benefits of integrating machine vision camera technologies. These include digital shutter sensors, high speed interfaces and a Software Development Kit provided by camera manufacturers such as Allied Vision Technologies.
Interline Frame Transfer CCDs and Global shutter CMOS devices have eliminated the dependence on a mechanical shutter; a necessity for ITS system providers who integrate high resolution SLR cameras which rely on a rolling shutter CMOS device. Like any other mechanical component, a mechanical shutter has a much shorter lifetime compared to a digital shutter often leading to system downtime and a costly maintenance budget.
Networking capabilities and long cable length support provided by high speed interfaces such as GigE Vision has allowed instant transportation of images to a central location, reducing police response time and improving traffic management. As an example, Allied Vision Technologies provides FireWire digital cameras with built-in optical fiber connectivity enabling several hundred meters of cable length, while conventional GigE Vision allows for up to 100 meter cable length with conventional Ethernet cabling. High data bandwidth sustained by GigE Vision cameras allows manufacturers to support high resolution imagers operating continuously at very high frame rates, 365 days a year.
Designed for system integration, machine vision cameras play well with others. The Software Development Kit and improved third party compatibility – for example provided by XML parsed feature understanding – allow integrators to develop ITS systems using a machine vision camera with relative ease. This also provides ITS system integrators with the ability to transition to different camera models without having to recreate the application software.
Machine vision cameras also offer many advanced features such as low latency trigger for timely image capture, flexible exposure, gain and binning modes to adapt to any outdoor lighting conditions, digital shutter (global shutter) and high sensitivity to minimize motion blur and image distortion, as well as configurable I/O to synchronize the image capture process with traffic system peripherals such as ground loop, radar or laser triggers and LED or xenon lighting. Some machine vision camera manufacturers are introducing new features specifically designed for the traffic market. Integrated lens control for instance, supported by the Prosilica GX family from Allied Vision Technologies, has allowed integrators to eliminate the lens control box previously necessary for anyone wanting to incorporate remote zoom, focus or iris lens control.
Smart City Solutions – The Future for China’s Streets
A new ITS project aiming to regulate traffic in one of China’s major metropolitan areas is currently under way. The project focuses on the study of the city’s traffic flow for the prevention of traffic jams and the reduction of traffic congestion. The system analyzes traffic density and average speed and automatically sends an alarm when a stalled or slow or illegally parked vehicle is detected. Further law enforcement installations are added such as LPR (License Plate Reading) to detect suspicious vehicles (vehicles with no license plate), or illegal use of lanes.
With further projects planned nation-wide China is leading the way in the development and implementation of Intelligent Transportation Systems while other countries, notably in Europe and North America, have seen ITS projects put on hold due to economical or political reasons. Let’s hope the Chinese example will provide government bodies in other countries with the motivation to evolve their own policies and treat ITS as a real solution to many law enforcement and infrastructure challenges that we currently face today.
*source: Ministry of Communication (2009)