Security systems for road tunnels.
Tunnels are complex, expensive technical structures. Security systems in them have a dual purpose. Firstly, as at any facility stuffed with expensive equipment, and even important for the life support of a city or region, a regular security system against criminals is needed, starting with protecting lamps from petty thieves and hooligans, and up to protecting hydraulic and engineering systems from terrorists. Secondly, the tunnel needs a technological system for monitoring the condition, as well as a system for supporting actions in emergency situations.
As for the first function, it is relatively simple and is solved, as in any large-sized facility, by a set of measures, including locks and sensors on all service doors, perimeter security and video surveillance systems, and access control systems to key rooms. Of course, in our case, the concept of «perimeter» is somewhat peculiar, because access to the inside of the tunnel is open to everyone. In reality, the main structural units that are critical for maintaining the strength of the tunnel are subject to protection, as well as utility rooms with special equipment, for example, fire extinguishing and ventilation system units.
The most interesting is the second function — more technological than security. Its purpose is to detect abnormal situations and overcome them.
The most common emergency situations are accidents in a road tunnel. In the simplest case, they lead to a long traffic jam and nervous drivers and passengers in a gas-polluted tunnel. In the worst case, accidents can be accompanied by a fire in spilled fuel, which is fraught with mass casualties. However, in any case, it is necessary to detect the emergency as quickly as possible and send the appropriate group — traffic police, firefighters, rescuers, builders …
I will not touch on fire alarms and fire extinguishing systems, this is described in detail in building codes. Unfortunately, in the case of a road tunnel, the fire alarm will only give a signal when there is almost no hope of avoiding casualties.
In fact, the only means of early detection of various abnormal situations is video surveillance. Manual observation by the operator is indispensable, because abnormal situations are abnormal because they are all special and unique. However, the operator is only a human being. Half an hour of sitting motionless in front of a screen with smoothly moving cars, and he sleeps with his eyes open, and now he is completely calmly watching (and not seeing) how a fuel tanker overturns in a tunnel.
Of course, it is necessary to use methods of psychological relief of operators, frequent change of duty officers, work in groups, but modern technology can also help the operator a little. For example, if some elements of video analytics are used.
Currently, the means for determining the speed and density of the flow of vehicles are working quite reliably. Automatic detection of differences in the flow at the entrance and exit (and it would be good to do this at several points along the length of the tunnel), detection of any deviations from the statistical norm for this time of day on this day of the week — all this allows you to draw the operator's attention to suspicious situations, and therefore increase the reliability of his work.
But detecting an emergency is only half the battle. When it happens (and they happen surprisingly often), it is necessary to inform people in the tunnel, manage their evacuation if necessary, and coordinate the actions of rescue teams. Therefore, emergency lighting systems, evacuation signs, and public address systems are necessary. To coordinate the actions of rescuers, a microcellular or similar multi-antenna system is necessary, because radio waves will not get into the tunnel by themselves.
It is essential that all the response teams involved have their representatives at the video surveillance point, so that there is no «broken telephone» from the video surveillance operator to the electricians, hydraulic engineers, rescuers, and firefighters. That is, not far from the tunnel itself there should be a full-scale situation center, where all interested services can simultaneously receive information. And observe current events, and view the recording of the incident itself, and receive telemetry information from technological systems.
It is highly desirable that video cameras remain operational for a sufficiently long time in an emergency situation, in particular, provide an acceptable image with emergency lighting, with the main equipment de-energized. Formally, fire resistance requirements are usually not put forward, but since the most serious cases are fires, then video cameras should also remain operational for at least tens of minutes in a fire. Do not forget that in addition to video cameras, the safety of cables is essential — they must be laid in steel pipes, if possible outside the tunnel. The location of video cameras should also facilitate their operation: they should be in points with minimal smoke during the operation of the smoke removal system.
The cramped space of the tunnel creates other additional problems. Firstly, video cameras are inevitably located very close to moving cars. While on highways video cameras can be raised higher or moved to the side, in a tunnel this is impossible, and all the dirt, dust, and splashes fly onto the video camera in full. Windscreen wipers on the video camera window are absolutely necessary, and it is desirable to equip the housings with a washer reservoir with an increased volume.
Dirt on highways in many cases also carries aggressive substances. Although in Moscow in recent years salt is usually not used in winter, nevertheless, the casings must have increased resistance to corrosion. Stainless steel casings are desirable, and most importantly, they must provide the maximum possible protection for the video camera itself, for which even the penetration of ordinary water, and especially in combination with oil, gasoline and soot is dangerous — after all, you can't put a wiper on the CCD itself inside the video camera. It is not for nothing that, for example, the Canadian Department of Transport recommends using the highest available protection category in tunnels: marine explosion-proof design of video cameras.
Finally, the cramped space and the presence of powerful energy consumers in combination with multiple internal combustion engines are a serious source of electromagnetic interference. However, this problem is easily solved by installing a fiber-optic line, especially since the distances in the tunnel often exceed the 200-300 meters allowed for copper transmission lines. Now there is even a choice — to use direct video signal transmission without loss of quality, or video signal compression on site and transmission over standard computer networks.
Do not forget to provide high-quality video recording of incidents. This is necessary both for subsequent analysis to avoid repeating mistakes, and, often, for legal proceedings — accidents in tunnels can have very serious consequences. It is important to exclude the possibility of accidental erasure of the video recording of the incident. Video recordings of emergency situations must be stored for at least 3 months, and preferably 3 years (the statute of limitations for civil cases).