Sometimes that elevator works. Photo: Hiroko Masuike/The New York Times

It’s difficult to remember pain when you’re not feeling it, and harder still to imagine living with physical limits you don’t actually have. But all it takes is a brief stroll to see how badly designed the city is for those who are very young, old, short, heavy, frail, or in any way impaired. During one four-block expedition through my neighborhood, I observed a handful of incidents that ranged from the irritating to the potentially lethal. A young man couldn’t maneuver a stroller through a hardware store’s half-open entrance, so other customers fretted outside while a manager was summoned to unlock the other door. (A wheelchair would, of course, have faced the same barrier.) A woman with a walker inched across an avenue and found herself still a dozen feet from the sidewalk when the light turned, triggering a burst of impatient car horns. An aide pushing a man in a wheelchair hit a crack in the sidewalk so that her charge tipped dangerously forward. A woman yanked at the door to the subway station and discovered it was too heavy to budge.

I noticed potential hazards too. The pathway into the neighborhood park is a black-diamond slope, short and sheer; a construction crew diverted pedestrians into the street along a too-narrow lane; a truck stopped in a crosswalk blocked the curb cut, stranding pedestrians in the middle of traffic. You could catalogue hundreds of these obstacles on any day in almost any part of the city, though some places and times are worse. For many New Yorkers, a snowstorm is an occasion for ugly shoes. For those who can’t vault the mounds that snowplows deposit by the curb or ford the lakes of slush, it means a week of house arrest.

It shouldn’t be that hard to understand these impediments. Most of us have been injured at one time or another, and all of us have had the experience of feeling like guests in a world designed for others: It’s called childhood. We age in different ways, but nearly all of us will experience small glitches evolving into insurmountable barriers. And yet we resist understanding for as long as we can. Those of us who can walk, see, and hear all at the same time, and whose physiques cluster around the average, live in a world tailored to our specifications. I can get up from a park bench, turn a lock on a bathroom door, switch on a light, and stride through a turnstile without having to pause and consider how. For now, the price of my ease and confidence is someone else’s misery. But it doesn’t have to be that way.

The Americans With Disabilities Act, or ADA, which President George H.W. Bush signed into law in 1990, emancipated millions and set a standard for the rest of the world. It meant that, legally, any public place must accommodate anyone who wishes to go there; wherever there’s a stair, there must also be a lift or a ramp. It caused the proliferation of automated doors; forced schools to design programs for children with autism; helped boost a market for prosthetic fashion and products designed for arthritic hands; and launched new practices in street design, including textured curb cuts that alert the visually impaired that they’re about to step into traffic.

The ADA has been a boon, but it has also left a chasm between theory and reality. I recently scouted a restaurant with two steps down to the front entrance. Customers in wheelchairs are invited to take the ramp … that leads round the back, between the kitchen and the restrooms (but please wait outside until the staff has moved a stack of high chairs out of the way). In the case of New York’s public-transit system, the ADA functions as a kind of fond mirage, bobbing gently in a mythic future. Dustin Jones, a wheelchair user and disability-rights activist at the the Center for Independence of the Disabled New York, lives around the corner from the 149th Street subway station in Mott Haven, a straight, 25-minute shot on the No. 5 down to his office. at Union Square. But because neither station has an elevator, his commute requires several contortions: “I take a bus seven stops to the 6 train at Hunts Point, then go to 125th Street, where I transfer to the express to make up for lost time. At Grand Central, I switch back to the 6, take it to Third Avenue at 23rd Street, and take another bus to 14th Street. That trip is an hour and a half.”

The MTA has spent decades, at least since the ADA became law, pleading for patience. Installing elevators is slow and costly, the agency argues, but it’ll get there … sometime. Jones, along with various disability-rights organizations, has sued the MTA for being so slow to make the system usable. “The city does things half-assed,” he says. “There are so many civil-rights laws that protect people with disabilities, but when it comes to enforcement, nobody really cares.” (Vienna, another city with an old transit network, seems to have solved the problem handily.) In the meantime, the burden of compensating for a neglectful system falls on the injured, the sick, the disabled, and the old. We all suffer the consequences, though, just as we would all benefit from a habitat that was better conceived. People who can’t manage the subway’s endless stairs have to take cabs or car services, helping to clog the roads with traffic. That’s if they can find an accessible vehicle, and can afford to pay for it.

Americans with disabilities are chronically underemployed — fewer than 20 percent have jobs, according to the Bureau of Labor Statistics — which means that the nation is squandering an enormous talent pool. In a more equitable world, all the energy and tenacity that go into simply getting around would instead be devoted to starting businesses, writing plays, or combating climate change. When ordinary routines require constant, strenuous effort, the economy suffers.

New buildings mostly manage to avoid the worst embarrassments, but some architects still content themselves with grudging compliance. Dramatic staircases in academic buildings and offices often double as hangout spaces, which of course excludes anyone who can’t climb them from a slice of social life. The California-based firm Morphosis organized its Cooper Union academic building, which opened in 2009, around a wide vertical piazza that swoops up through the heart of the structure. In an attempt to channel students onto the stairs and keep them in shape, the elevators stop only on alternate floors. Students with disabilities can take a dedicated elevator just for them, a solution you might describe as separate but equal. A decade later, the centerpiece of Hudson Yards is Thomas Heatherwick’s Vessel, a 15-story structure made entirely of stairs, plus a couple of perfunctory elevators.

Complying with the ADA is like not robbing a bank: better than the alternative. And yet the bare-minimum approach permeates even a presumably enlightened university like Columbia, which prides itself on being an inclusive haven for scholars from all over the world. All across the Morningside Heights campus, gracious, century-old buildings have been retrofitted with off-the-shelf metal ramps that rattle and tilt, their segments joined by plastic speed bumps. See what you made us do?, they practically shout. The ramps do the job, but they are the architectural equivalent of closing up a wound with duct tape.

Updating historic buildings to render them more usable is never an easy or inexpensive task, but it’s made even more challenging by thinking of accessibility as a sop to contemporary sensitivities. David Gissen had bone cancer as a teenager and was in architecture school when he underwent surgery to remove his leg. When he realized he wouldn’t be able to navigate construction sites, which aren’t covered by the ADA, he switched paths and became an architectural historian instead. (He is now a professor at the California College of the Arts.) Having traded in his wheelchair for a prosthetic leg, he struggled up countless stairs to the top of the Acropolis in Athens, a climb that 19th-century poets, painters, and archaeologists equated with the arduous labors of enlightenment and spiritual growth. Later, he discovered that in the sixth century B.C., a wide gentle ramp led from Athens’s low-lying marketplace to the mountaintop temple.

“The ramp,” Gissen wrote, “was a key element in transforming the Acropolis from a feudal bastion to a religious and civic site … the elderly and very young children joined others on the upward pilgrimage — some walking, others on horseback or in carriages.” To Gissen, the obliteration of that ancient ramp suggests that accessibility is not just a modern concept. Preservationists, he says, should stop reflexively thinking of it as the opposite of authenticity.

Disabilities come in countless forms and present an immense array of challenges that will be met only by a whole new era of creative thinking. “The New York City subway is a challenge for everyone, but mine begins with purchasing a ticket: I can’t reach the machines, even the accessible ones,” says Sinéad Burke, an Irish activist with dwarfism, who stands three feet, five inches tall. Burke can tick off the frustrations she encounters every few minutes of every day: the bank tellers who can’t see her, the maître d’ who mistakes her for a child, the passersby who shout rude jokes, the innumerable times she has to ask total strangers for help.

“My idyll would be to have the same independence you do, and have that so deeply ingrained in me,” she says. But people can adapt more quickly than buildings, buses, and streets. “When design is flawed, it’s an intergenerational project to fix it. In the interim we can deal with it through changes in the culture. We need to find a way of amplifying the voices of those who need assistance or would like to have the option of declining it.” Burke suggests that people with disabilities might, for instance, wear an instantly recognizable badge that would signal to passengers on a subway car, for instance, that they might offer to give up their seat. (That’s if they can get on the car at all.)

Burke says that the culture is changing, and the “intergenerational project” of redesigning cities for everyone has already begun. A combination of technology, activism, litigation, and resourcefulness is dragging the business of building into an era of more empathic design. Some designs cater to particular populations, such as people with autism or Alzheimer’s. The state of the art in inclusive architecture is probably the Musholm Sports Center in Denmark, where every detail is geared to helping people with physiques of every variety move, play, and sweat.

But it will take some fundamental changes in attitude and education. Instead of resenting the demands of the disabled as roadblocks, architects can and should treat them as sources of inspiration. They might, for example, sign on to the goals of universal design, which is based on the principle that making a place more practical for some winds up making it more convivial for all.

“Most designers have a negative attitude towards accessibility,” says Lisa Switkin, a senior principal at the ubiquitous landscape design firm Field Operations. “They think of it as something you have to do, using as little square footage as possible. For us, it’s part of the design philosophy. When you really know the rules, you can integrate them into the geometry of the space.” At Tongva Park in Santa Monica, Switkin’s firm sculpted a new topography: Gently rising pathways wind their way past an artificial waterfall and cactus beds, up to a romantic lookout over the Pacific Ocean. The result is not just a terrain that virtually everyone can navigate but a slow, contemplative trajectory that packs a lot of experience into a limited number of acres. The park’s success makes it clear that design has a central role to play in breaking down the way society sorts and segregates. When I ask Burke what she would say to a roomful of architects, she has an instant response: “Make accessibility beautiful.”