LONDON . In Vietnam, where I recently spent a week, streets are a sea of scooters and small motorcycles. Saigon, or Ho Chi Minh City if you insist, buzzes to the eddying of this two-wheeled tide. Entire families perch themselves on bikes, often with a small child up front who gets the best view, the hot breeze in her face and, of course, the least chance of emerging unscathed from a collision. Adults wear helmets; children and live animals do not.

Along with the living --- a chicken or piglet perhaps --- various things may be wedged at angles, including small refrigerators, potted plants, metal frames and bunches of bananas. Bikes, the cars of the newly affluent, and pedestrians weave around one another in a seamless pattern fashioned not by any rule or organizing principle but by individual awareness. Major intersections, unburdened by anything as cumbersome or inflexible as traffic lights, function as massive group exercises in tentative advance, the principle being to coax others to the prudence of the brake by nosing ahead with just the right dose of insistence. Lo, the sea divides. A path opens. There is no logic at work, but there is a great deal of humanity.

Madness might be a verdict on all this, but then to the average Vietnamese biker there might be equal madness to Western culture, hemmed in by all the controls that a combination of fear and technology produce. Surely there must be a happy medium between placing a toddler on the handlebars of a scooter and denying children the freedom to roam and discover that is essential to their development. Surely there is an appropriate balance between a free-for-all on the roads and a camera at every corner. But humanity tends to deal more in irrational exuberances than happy mediums. The pendulum swings too far.

In Britain, over-the-top safety obsessions have produced a society where cameras and so-called traffic-calming speed bumps are everywhere, visitors to churches and colleges are warned that medieval paving stones may be a little uneven, schoolchildren have been advised to wear goggles when using certain glues (and helmets under chestnut trees), trainee hairdressers are not allowed scissors in the classroom, and mail delivery gets suspended in an entire region if a postman slips and hurts his shoulder. David Cameron, the prime minister, spoke out five years ago against the health-and-safety culture that had produced “a stultifying blanket of bureaucracy, suspicion and fear that has saturated our country, covering the actions of millions of individuals.” Not much has changed.

Britain is only an extreme example of the broader phenomenon that can see the world’s greatest city, New York, shut down not by a snowstorm but by the possibility of a snowstorm (the blizzard that never happened); and the bizarre term “free-range parenting” applied to American moms and dads who believe their children should be allowed to walk home from school alone and play outside. Earlier this year a Maryland couple was found responsible for “child neglect” because they let kids walk home alone from a neighborhood park. Whatever happened to the land of the free and home of the brave?

I am not recommending that Western urban planners go to Vietnam to study traffic management. I am suggesting that developed Western societies, increasingly fear-driven, tend to fall into a nanny-state mind-set where health, safety and security must all be stringently regulated, adults are viewed as children, and the emotional intelligence of humanity is underestimated or discounted. To cross a highway in Saigon . perhaps with a wave here and there to remind onrushing scooters and cars of your existence . is to experience not just relief at reaching the other side, but wonderment at how unregulated people can work together.

The Dutch traffic engineer Hans Monderman was intrigued by this phenomenon. His “shared space” idea turned traditional thinking about road safety on its head. For much of the 20th century the assumption was that efficient traffic flow depended on a full separation of cars and pedestrians, complemented by traffic signals, signs, barriers and road markings that would keep people safe. The state took charge through regulation; the individual only had to obey instructions.

Monderman, who died in 2008, had other ideas. He wanted to raise collective awareness and responsibility by doing away with all that separateness, and he believed that safety might be increased by making all travelers intensely aware of one another. Cars, bicyclists and pedestrians would all move on a single curb-free surface, without sidewalks or signs. Sometimes he would test his schemes . developed in various Dutch, German and Scandinavian towns . by walking backward into dense traffic in a shared-space area. Of late the idea of “shared space” has even gained a foothold in London.

I recommend walking backward into a Saigon street, for the heck of it, but also to be reminded of the limits of regulation and the power of shared humanity.