In ancient Pompeii, if you walk northeast along the wide Via dell\u2019Abbondanza, then cut right onto the narrower Via Nocera for a block, then turn left onto Via di Castricio, you\u2019ll approach the southeastern corner of the city, where the road again opens wide to the Anfiteatro, Pompeii\u2019s stadium, preserved remarkably well by the thick blanket of Vesuvian ash that covered it for about 1,700 years.When G. Keith Still took this walk for the first time nearly 11 years ago and went inside the stadium, he sensed a paradox. In many ways it felt just like modern stadiums. That\u2019s not surprising; the design ethic of modern arenas still borrows liberally from classical Greek and Roman architecture.Picture's worth 1,000 words? Then you'll like The Illustrated Guide to Security, featuring dynamic visual presentation of a dozen critical security issues [CSO Insider registration required]But at the same time, Still, a world-leading expert on crowd management who has consulted on some of the biggest crowd-\u00adcontrol events in the world, including the Haj pilgrimage to Mecca and the upcoming Beijing Olympics, felt something different from today\u2019s stadiums at Pompeii. \u201cEverything seemed so much easier,\u201d he says. \u201cThere was enough space for everyone. Entrance and exit were simple, elegant. It wasn\u2019t just a stadium, it was an integrated part of the city design.\u201dFrom a crowd management perspective, Still says, Pompeii\u2019s stadium is an excellent design, and one worth learning from. Of course, Still understands that modern facilities are looking at economic payback and long-term sustainability and because of that often work with limited space. Still argues, however, that facilities are designed to maximize profit at the expense of creating safe crowd conditions. \u201cThey don\u2019t design for the safe movement of people,\u201d he says. \u201cArchitects borrow from history. They co-opt features of ancient facilities without understanding the broader context. They\u2019ll spend years studying design and structures and spend a couple of weeks on crowds. They say \u2018Let\u2019s put it here, then figure out how to get people in and out.\u2019There\u2019s scope for improvement, we\u2019ll put it that way.\u201dImprovement can come from studying sites like Pompeii, Still says, and then trying to balance the profit motive with some of the ancient stadium\u2019s crowd management features that can significantly reduce the risk of often tragic and too-common security events\u2014crowd disasters.Stampedes, crushes, riots. In crowds, trivial events can have tragic consequences. In a Chinese school last year, a child stopping in a stairwell to tie his shoe spurred a crush that killed six. The belligerent few can sway thousands of normally well-behaved individuals to riot, as soccer hooligans in Italy did earlier this year. Still shows video from an outdoor rock concert in which a few kids dancing fall down and cause, in seconds, a wave of hundreds of collapsing bodies, as if cuffed by the hand of an invisible giant.Crowd behavior can be so distinct from individual behavior that the crowd is thought of as one thing, a kind of superorganism with its own psychology. Back when Pompeii\u2019s amphitheater still hosted gladiatorial spectacles, Titus Livius (Livy) complained that crowds are \u201ceither humble and servile or arrogant and dominating\u2026incapable of making moderate use of freedom.\u201d Gustave le Bon, who wrote about group psychology in the early 20th century, said we must either figure out the psychology of crowds or \u201cresign ourselves to being devoured by them.\u201dNo security phenomenon is as volatile, none can flip from managed to chaotic as quickly as a crowd. That\u2019s why professionals such as Still are concerned by poor design in modern stadiums. (Still says he\u2019s also concerned about a marketing trend where companies harness crowds to generate buzz, a phenomenon called \u201ccrowd crazing.\u201d The tightly hyped launch of a video game system, for example, has spurred violence, as have discount bridal gown shopping events, the grand opening of Ikea furniture stores and the lead-up to a sporting event between rivals.)For a long time, the crowd itself, the mob mentality, mass panic, was inevitably blamed for disasters. But in the past decade, the science of crowd dynamics has undergone a broad philosophical shift, led by experts like Still who suggest that the mob mentality is a myth. Using computer modeling that combines a wide breadth of knowledge, from architecture and design to human physiology and psychology, Still has upended the assumption that the crowd causes disaster, and underneath that assumption he has found that it\u2019s possible to manage the risk inherent in crowd dynamics and reduce the possibility of disaster.\u201cIt\u2019s not a stampede, it\u2019s a design and management problem,\u201d says Still. \u201cThe stampede is the effect, not the cause. It\u2019s an entirely predictable crowd dynamic. We can tell you what factors give rise to that behavior and how to engineer a system to limit it.\u201cAnd, lo and behold,\u201d he says, explaining the paradox he sensed in Pompeii\u2019s amphitheater that day, \u201cif you look at Pompeii stadium, 2,000 years ago, they did this incredibly well.\u201d When he compares the Pompeii stadium\u2019s design to what computer models tell him is good crowd management design, \u201cthe geometry, the ratios and spaces at Pompeii, they are all optimal.\u201dTurn the page for a tour of Pompeii\u2019s Anfiteatro, and what makes its design, from a crowd dynamics standpoint, optimal.Build a Big Bathroom. Pompeii amphitheater\u2019s bathroom is the design element most distinct from modern stadiums. In fact, there was only one public toilet, and it wasn\u2019t in the stadium, it was next to it. The toilets were part of a larger structure, called a palaestra. Originally in ancient Greece, a palaestra was a gymnasium complex, but here its function was broader. People gathered here during events. Likely they conducted business and got food and drink here too. The palaestra was effective because it was huge, the size of four and a half football fields; its footprint roughly matches the stadium\u2019s. The public pool at its center, with a 3-foot shallow end and 8-foot deep end, was 75 feet wide by 115 feet long. \u201cNot only were there plenty of toilets,\u201d says Still, \u201cbut the route to and from them allowed for a wide dispersal of people.\u201d In modern facilities, there are many small bathrooms that endure rushes during intermissions, and the path usually narrows at the bathroom\u2019s entrance. Still says modern stadiums should build more and bigger bathrooms, give patrons large areas to line up outside of them and, as much as possible, separate their location from the stadium\u2019s main traffic. At Pompeii, he says, \u201cthey clearly planned for the rush that would occur at the end of a spectacle. You had the same human needs\u201d\u2014to visit rest rooms\u2014\u201cbut the layout and design made the whole dynamic of moving to and from much better.\u201dSeparate Queues from Promenades. Moving the bathroom and concessions next to the stadium instead of inside carried the added benefit of keeping those who were standing around separate from those who were walking to and from their seats. Good crowd management relies on keeping people moving at their comfortable pace of about 1 to 1.3 meters per second. Putting lines for the loo and for hotdogs in the same places where people walk creates clustering and disrupts that natural pace. This not only creates anxiety and frustration, but it also has a domino effect, creating congestion far away from the source, the same way it does on a busy road when cars accelerate and slow down. If modern stadiums aren\u2019t going to separate the bathrooms from the venue entirely\u2014and they\u2019re not\u2014Still says they need to create wider spaces around the perimeter that can be divided into a walking concourse and concourse for bathroom and concessions outside of that walking lane with broad entry and exits spaces between the two.Open Open Open! Here\u2019s a challenge: Look for areas of Pompeii\u2019s stadium where bottlenecks might occur, where the crowd could overwhelm a space. Still says you won\u2019t find them. Seats are at the optimum viewing angle, and seating \u201cpacking densities are to comfort, not cost.\u201d Again, Romans weren\u2019t worried about ROI, but Still maintains that compromise is needed in modern facilities to reduce the risk of crowd disasters. At Pompeii, spectators would have at least twice the personal space in their seats as a modern fan. Stairways to the concourse present themselves at angles that keep people moving, and they\u2019re as wide as the concourses they link to. On the side of the stadium where the city wall comes to a corner, there are no stairs, which would have forced people into tight spaces. Exits from the stadium to the palaestra, called vomitories, span the entire western side of the space, and that space itself isn\u2019t blocked off at its north and south extremities. Instead, it opens to wide roads, allowing for people to spill out into the city and toward gates that leave the town. The combined effect of all these design elements, Still says, is palpable. \u201cPhysically it\u2019s the same size as a modern facility, but the perception of space is significantly different. In a place like Wembley [Stadium in London, one Still has studied], you feel somewhat oppressed, closed in.\u201d In Pompeii, it\u2019s so open you feel almost insignificant but also part of the spectacle. To do this today, Still says, requires forethought all the way back to site choice. Often, he says, architects and planners put aesthetics (like a skyline or waterfront view) before safety as they try to shoehorn large venues into spaces that won\u2019t allow for the kind of openness crowds need.Build a Big Road. Still suggests that designs for roads and walkways leading to a stadium consider the facility\u2019s capacity. Ancient stadiums, notably Pompeii\u2019s and an earlier great theater, Ephesus, met this criterion. It might seem an overly generous sidewalk until you realize that the capacity at Pompeii\u2019s stadium roughly equaled the 30,000 population. Still says: \u201cI imagine an entire city descending on the site,\u201d then a generously broad thoroughfare starts to make sense. Still says newer facilities do this better than older ones, but urban facilities still struggle because of space limitations.Limit Corners. Modern stadiums often maintain the oval seating but then put blocky concourses around it. They also use switchback walkways and stairs. All of that creates corners. Corners force people to slow down and encourage congestion. Pompeii\u2019s concourses were elliptical; few corners exist to slow people down. Still says this also evened out flow to the vomitories as people could, like liquid, choose the path of least resistance easily without interrupting their pace. Ironically, says Still, it could have been the limitations of their materials that caused Romans to adhere to this principle. They simply couldn\u2019t build stone staircases into tight switchback configurations as we do with forged steel today. Still says architects should spend more time studying crowd dynamics to inform their design choices.Limit Options. In crowd management, the maxim called Braess\u2019 paradox states that more options equals decreased performance. That is, if you give people many routes to choose from, crowd traffic will slow down because of indecisiveness and selfish behavior when choosing one of the paths. Pompeii provides a stark example of avoiding Braess\u2019 paradox. The entire stadium is serviced by just six stairways, all of which point in the same general direction\u2014northwest. By the time a Roman would have to make a decision which way to go, the space has already opened wide.Anxiety Control. A commitment to openness at ancient stadiums reflects an understanding of hard sciences like engineering and geometry, but Still believes it also reflects the ancient Romans\u2019 understanding of human behavior. Openness reduces anxiety, and controlling anxiety is a cornerstone of crowd management. This combination of hard and soft sciences is what Still believes is lacking with many projects today. Still says facility managers \u201ccan shift the behavior of a crowd. Good signage and lighting, for example, will reduce anxiety. People need information before they approach the crowd. If one person has to ask where their seat is, then 140 people have to ask. Now there\u2019s a backup and people are frustrated. Now those frustrated people sense disorganization and start acting out. Others take that cue and the anxiety feeds on itself. People say it\u2019s the crowd\u2019s fault. No. As the facility managers, you shape the behavior. Your failure to provide certain information or anticipate what creates problems, or to react properly when something does happen is what turns the crowd ugly.\u201d In Pompeii, Still believes, Romans calmed crowds through design, even if they didn\u2019t think of it that way. After all, a bad call by an official can spark a melee today. In ancient Pompeii, gladiatorial spectacles fed violence and death to a crowd full of men with swords.Nuceria vs. Pompeii. During games between bitter rivals Pompeii and neighboring Nuceria in A.D. 59, the historian Tacitus writes of an altercation that \u201carose out of a trifling incident at a gladiatorial show. During an exchange of taunts...abuse led to stone-throwing, and then swords were drawn.\u201d Because of the incident, games were banned at the Pompeii stadium for 10 years (though this penalty doesn\u2019t seem to have been enforced). This might seem to disprove Still\u2019s notion of best practices in ancient crowd control. To the contrary, Still says. \u201cThink of the fact they could have a sword fight in the stands, what that meant about how they had very free movement in the stands. And because of the space, people could cluster away from the small pockets of danger, preventing small incidents from becoming bigger ones.\u201d The violence, in other words, was not a stampede or a crush. Today, nearly all crowd incidents affect the innocent, who simply can\u2019t escape.Respect Personal Space. There are benchmarks that Still uses and the United Kingdom has adopted for crowd densities to prevent people from getting anxious. None would have been crossed at a typical event at Pompeii stadium:\t2 to 3 people per square meter when moving\t5 people per square meter when standing or sitting\t6 people per square meter for up to six minutes in certain situations, such as an entrance queue, if the space is monitored.24 August, A.D. 79. Pliny the Younger wrote two letters to Tacitus about the day Vesuvius erupted and how Pompeii was erased from the earth. Pliny the Younger was in Misenum, across the Bay of Naples from Pompeii, reading Livy. When the cloud of burning ash finally rained down on the town, he and his mother fled. \u201cA dazed crowd follows us, preferring our plan to their own (this is what passes for wisdom in a panic),\u201d he wrote. \u201cTheir numbers are so large that they slow our departure, and then sweep us along,\u201d a description that sounds remarkably like a crowd crush, one that Pliny and his mother survived.But by then, Pompeii\u2019s Anfiteatro was gone. Its elegant geometry, its ideal use of space and its beautiful openness were smothered, and preserved, under 10 feet of hot ash and pumice.