Doorway and Entrance Point Tailgate Detection

Today's sophisticated access control systems are designed to help us control and manage who gets into our buildings and what times and days their access is allowed. The systems vary greatly in their size, scope, and method; however, they are all designed to make sure we know who is in the building. A major challenge faced by security professionals at major corporations, campuses and government institutions, is knowing that every person passing into their controlled access environment has actually presented a valid and authorized card, biometric identification, or author credentials. Simple card reader/door strike solutions at door entrance points are not effective for deterring and preventing unauthorized access by persons who might "slip in behind" a well meaning valid cardholder. Most time, these tailgaters or piggybackers mean no harm; they might just have their hands full, or maybe left their access card/credentials at home. However, by allowing such behavior, we "open the door" so to speak, to the possibility of an unwanted intruder entering our controlled access building.

So how are today's modern buildings being equipped to prevent such tailgaters and piggybackers? The use of optical turnstiles (with/without barrier arms or glass barrier wings) has been commonplace for the past 10-15 years, and has become even more prevalent after 9-11-01. But what is being done to protect our side entrances, doorways from parking garages and public areas, hallways between secure areas, and high security sensitive area entrances within the buildings? Actually, very little has been done up until very recently.

A number of potential solutions have been offered for the doorway tailgating problem. Some of the optical turnstile manufacturers have developed some pretty cool "doorway detectors" which act like a miniature optical turnstile, but that fit right up alongside the door jamb. However, this solution does not easily distinguish direction of the pedestrian (in vs. out), nor does it effectively count side-by-side pedestrians. The limitation of these systems lie in the fact that it can only can count the number of times that the infra-red beam pattern is broken. Wide doorways or double doors are a particularly troublesome challenge for this "door mounted tailgate detector" or "doorway detective" type system.

Potential answers to these challenges has come to us from a variety of companies with varying technological solutions. It seems to be agreed that the detection of unauthorized pedestrians comes from above. In other words, some sort of ceiling mounted or otherwise overhead located sensors or cameras may hold the key to preventing tailgating and piggybacking. These solutions have been tested to varying degrees by a number of integrated security technology professionals, with some measures of success.

Let's look at three of the overhead sensor technologies briefly here. The stereo vision camera systems have had some limited success in certain environments but may be limited as to their throughput potential and ability to resist overheating. Thermal image cameras are a potential solution assuming that external light sources (daylight especially) are kept to a minimum, which has only limited application. The seemingly best solution offered is a 3D sensor using MLI (Modulated Light Intensity) technology. Using time-of-flight light measurement, a 3D MLI sensor or camera can measure and process data very effectively so as to easily distinguish between heads (at various heights), objects, and baggage. In practical applications the 3DMLI system does very well in height volume multi directional traffic areas, with an accuracy rate in the 98% range. Check out http://www.ieesensing.com/ in the Public & Commercial Infrastructure section for info on the system offered by IEE Sensing of Auburn Hills, MI, and Contern, Luxembourg.