Pictures Through The Air

Nov 1, 2007 12:00 PM, By Michael Fickes

Terrorist attacks on mass transit vehicles in Madrid and London have led transportation authorities across the United States to seek out ways to prevent or mitigate the effects of such an attack on one of their commuter trains or buses.

Scotland Yard, the headquarters of the Metropolitan Police Service responsible for policing Greater London, reviewed hour after hour of footage while looking for the terrorists that bombed three underground trains and a bus in July 2005, proving the usefulness of video for investigating acts of terrorism and crime.

Unfortunately, video systems that do not have wireless capability can only help investigate an incident. They cannot prevent or mitigate a crime or attack.

Today, with the emergence of new wireless broadband transmission technologies, video surveillance cameras installed on mass transit vehicles can potentially help prevent crimes or attacks or at least mitigate their severity by accelerating the emergency response.

For example, the Massachusetts Bay Transportation Authority (MBTA), the fifth busiest transit system in the United States, has equipped its buses with wireless video technology capable of sending video to nearby police cars. “When the police car comes within range, wireless technology on the bus forms a network with wireless technology in the police car,” explains Michael Dillon, vice president of business development with Los Gatos, Calif.-based Firetide Inc., which supplied MBTA with the technology.

Officers in the car can access cameras inside the bus and see what is happening, continues Dillon.

How the technology works

Video from the systems travels across a wireless network, usually installed by a municipality for use by all emergency response agencies, including police, fire and medical.

Groups of inexpensive small nodes, each capable of receiving and transmitting digital signals, make up the so-called mesh networks often used in such systems. The nodes are placed on poles or other structures that typically line city streets. For subway and train coverage, nodes can sit on the walls of a tunnel and on structures near above ground train tracks. “I can input data into mesh nodes that enable them to recognize each other and to operate as a network,” Dillon says.

Each node communicates with the three or four nodes closest to it, and in this way forms a wireless cable capable of transmitting voice, data and video information.

In the case of the MBTA system, there is a node on the bus and a node in the police car. When the police car comes within range of the node on the bus, the two nodes communicate, and the officers can access the video with an 802.11 receiver connected to a laptop.

In some ways, a wireless mesh network is better than a wire because it is self-healing. In other words, if one node fails, the connection doesn't fail. Because each node communicates with several nodes, the network can create a new route for the signals to follow.

Some of the nodes in a system connect by wire to the Internet. Those connections enable municipal agencies to access the network from a computer at work or at home.

In the case of a transit agency, a wireless video system won't maintain constant contact with headquarters. A transit authority will equip thousands of buses and train cars with video cameras and digital video recorders (DVRs). Trying to send all that video would overwhelm a network.

Instead, a driver will use a radio to call the police and a manager, and then they will access the video. If the driver cannot use the radio to call for help, he or she can press a panic button that sends an emergency alert again over the radio.

“Our system ties into the panic button,” says Philip McDouall, director of transportation product marketing with March Networks Inc. in Ottawa, Quebec. “When a driver or train operator presses a panic button, the system will mark the video for up to 30 minutes before and after the panic button signal. The usual length of time is 10 minutes before and after.”

“When the vehicle gets within range of a wireless node, it will automatically download the video to a network server at the transit agency and send an e-mail to the system administrator saying that emergency video has been delivered,” he says.

Cameras and DVRs

Mass transit agencies in the United States have used video for years as a means of investigating liability claims. With those systems, the bus driver or train operator periodically removes the hard disk from the onboard DVR and delivers it to the office. If an incident turns into a personal liability claim, the video is available for review.

So agencies are accustomed to putting video cameras and recording devices onto buses and train cars.

An average 40-foot-long bus will carry eight cameras: four inside and four outside. Inside the bus, two cameras are mounted near the ceiling at each end of the aisle and look down the aisle. The other two cameras watch the two doors and record people getting onto the bus.

Outside the bus, one camera looks straight ahead to capture accidents that may occur. On the curbside of the bus, one camera watches people getting on and off. A roadside camera looks for accidents there. And finally, there is a camera on the rear of the bus looking back.

According to McDouall, light rail and passenger trains carry fewer cameras outside than buses. There is a forward camera that looks ahead. Some operators also use a curbside camera for exiting passengers. Inside the train car, two cameras look down the aisle from either end of the car, and other cameras watch the doors.

The vibration of a moving vehicle requires that the manufacturer ruggedize the cameras. In addition, the cameras are fixed and have no pan/tilt/zoom capability. Lenses require wide dynamic range (WDR) capability to limit glare when the camera is looking directly into the sun. As with all security cameras that operate at night, mass transit cameras must be able to switch to black-and-white, which produces better images after dark.

Coaxial cable runs inside the bus side panels and connects the cameras to the DVR, which is located in a cabinet directly behind the driver's seat.

A ruggedized DVR designed for mass transit vehicles features an isolated or suspended hard drive to prevent the drive head from skipping when the vehicle hits a bump.

Top manufacturers also include ingress protection (IP) ratings with their DVR specifications. Based on an International Electro-technical Commission (IEC) standard, the IP rating expresses how well a DVR cabinet protects the drive from water, moisture and dust. Some manufacturers also seal circuit boards with thick layers of varnish, which prevents moisture from getting to the components, while keeping them in place.

McDouall says that mass transit vehicles can use a 2.5-in. or 3.5-in. hard drive. “The 2.5-in. drives have a capacity of 160 gigabytes,” he says. “That will enable an eight-camera system operating at a moderate frame rate to provide about 14 days of coverage.”

The 3.5-in. drives are new and can store up to 1 terabyte of video.

The mechanical nature of the hard drives makes them the weak link in an onboard video system, wireless or not. “We buy the best hard drives on the market, which are from Seagate,” McDouall says. “Still, it is the only moving part in a DVR except for a couple of small fans.”

“We're watching solid state memory technology closely. Today you can buy 32-GB memory chips at a reasonable cost. The largest available is 250-GB, but at that size, it costs well over $1,000, compared to $400 for a 1-TB hard drive. But like all technology, prices are falling for solid state memory, and we believe it will be affordable within a few years.”

Installing wireless video systems

Bus and train manufacturers typically install onboard video systems. “When we make a sale to a transit authority, they will specify that the equipment be built into the vehicle at the time of manufacturer,” McDouall says.

March Networks has a team that trains manufacturers to install the systems. Another team trains local bus and train mechanics to retrofit existing vehicles with camera and DVR systems. But McDouall says that retrofits are expensive. “You have to tear the vehicle apart to do it,” he says.

Transportation authorities in many major metropolitan areas have installed cameras on buses and trains, paying the $10,000 cost per vehicle with grants from the Department of Homeland Security (DHS).

While the installed base of wireless mesh networks is not yet widespread, municipal, state and federal governments are considering the technology as part of their emergency response planning. As a result, wireless video systems like that operated by MBTA are beginning to appear around the country.

Firetide is installing a mesh network and wireless video surveillance system in Glendale, Colo. The Dallas Police Department installed a Firetide mesh network in its central business district in a bid to control rising crime. The Phoenix Police Department has installed a Firetide mesh network designed to support investigations that require the swift installation of a video surveillance system.

Return-on-investment

While mesh networks are costly, Firetide's Dillon notes that the technology can provide a return-on-investment (ROI) for buyers. “Many of our customers are installing multi-purpose networks provisioned so that their mission-critical applications run on a certain segment of the network, with excess capacity reserved for public uses,” he says.

For instance, a mesh network can provide WiFi hotspots. In a community equipped with a mesh network, the transportation authority could offer Internet connectivity to train and bus riders, making mass transportation more attractive to commuters and helping to boost ridership.

In Corpus Christi, Texas, a meter-reader from the gas and electric company was attacked and mauled by a dog. The shocked community decided to roll out a mesh network and convert to automated meters that can be read over the Internet.

Mass transit vehicles equipped with video cameras are also equipped with liability protection against false claims. Front-facing cameras, roadside cameras and rear cameras on buses will record accidents with other vehicles and provide proof of who is at fault. Similarly, cameras watching the doors from inside and out will record slip-and-fall incidents when they occur — and not when they do not occur. The aisle cameras will help verify “slip-and-fall” claims too.

March Networks includes audio capability with its camera systems to help limit liability. “Audio is helpful when a rider complains about how an operator treated him or her,” McDouall says. “The audio will prove or disprove an accusation. In my experience, operators are usually exonerated.”

Perhaps the most interesting ROI concept involves selling time on the network to advertisers. According to Dillon, a mesh network makes it possible to localize advertising over the Internet.

Laptops, smart phones, PDAs and other electronic devices that people carry all have Media Access Control (MAC) addresses. It is possible to monitor the MAC addresses passing a location. Suppose a public bus route passes by a Macy's department store that has set up a monitoring system. The store could then mine the data it collected and discover that certain MAC addresses appear in front of the store virtually every day. Macy's could then send an advertisement tailored to MAC address.

Dillon says that economic models for such advertising already exist. “The pricing ranges from 75 cents to $2 per impression,” he says.

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© 2008 Penton Media Inc.

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