It's a scene as old as time: white hills pocked with sledders after a fresh, powdery snowfall.

But the times they are a changin'.

The sleds may be more durable and the snow gear more water-repellent, but the biggest transformation in sledding these days is the gaggle of nearby parents - acting as traffic controllers, rule enforcers, and fashion police to kids as old as 15.

It was, of course, the next freewheeling kid activity (next to play dates, organized sports, and birthday parties) ripe for supervision by a generation of helicopter drivers. And the phenomenon, child-development experts say, is likely not good.

Wendy Mogel, author of the best-selling parenting books The Blessing of a Skinned Knee and The Blessing of a B Minus, finds the latest in sled micromanaging "heartbreaking" - but also dangerous.

"Hover, protect, assist, run interference for children, and then we send them off to college, where they have magically acquired street smarts, maturity, and good radar through daily living or one of their AP classes," said Mogel, a clinical psychologist. "But there's a giant piece missing in between."

That piece, she said, includes sledding in the neighborhood. It's a simple, time-tested, low- or no-cost activity that gives kids an opportunity to figure out how to stay safe and have fun in a potentially risky situation.

They must calculate the quality of the snow, the steepness of the incline, the speed of their own sled, and choreographing a non-collision course.

"That's what you want to do in all of life," Mogel said. "Have excitement, adventure, and be a member of a team without having dangerous consequences."

Steven Goldberg, 44, the Voorhees dad of Zoe, 14, and Zara, 10, instinctively knows that's true - he went sledding without his parents when he was younger and came out unscathed.

"We'd have to trudge through a foot and a half of snow with our sleds to get to the hill," he recalled. But he's overwhelmed by his greater concerns for his daughters' safety.

"It's based in fear and access to information," he said. "When I was a kid, we didn't have the Internet and a constant barrage of hearing someone a town over was abducted or there's a sex offender living in your neighborhood. We didn't know that stuff."

He worries that he's setting his kids up to be equally afraid, and to remain too innocent for too long.

"Being able to make decisions is how you learn," he acknowledged. "They haven't experienced anything, so everything's in their imagination. The reality is things happen, kids get hurt, they get scared, and they get over it and learn."

Mogel urges parents to resist having a shortsighted or "worst first" view. Children need to learn independence and accountability just as much as - if not more than - they need to be protected, she said. If parents don't respect that need, "they are likely to face a surprise awakening when their child leaves home so fragile and unhappy that they come right back or text Mom every single time they hit a rough patch."

After the year's first big snow, Cade Rooney, 13, of Berwyn went sledding for the first time without parental supervision.

Though he enjoyed the freedom of being on his own - "you get to go down bigger hills," he said - he also liked it when his family was doing it together. That said, now that he's in charge of his own safety, "I'll think about if there's a tree or other obstacle and find a safe path. If the hill goes down to a road, I'll make sure I jump off before I get close."

He knows the risks, having once witnessed another child taken to the hospital after plowing into a swing set.

To that inevitable outcome, Mogel says there's a difference between being neglectful or encouraging recklessness and educating children about what to watch for on a hill of trees and toddlers. Experienced grown-ups also might admit: It's hard to know how to navigate a hill until you've actually done it - which brings Mogel to her next point:

Put money in an emergency-room account - "that's an investment in their child's future."

Despite the increase in parental supervision, Sameer Sinha, an attending physician in Jefferson University Hospital's emergency department, hasn't seen the number of sledding injuries - mostly sprained wrists and ankles - decrease. "We are just more aware of them, especially head injuries like concussions," he said. "They get more media coverage as well as more research than there was 30 or 40 years ago."

Sledding rules should mirror common sense, he said: "Pay attention to your surroundings, use sound judgment, and be properly bundled up, in hats, scarves, and gloves."

As for the sleds themselves, the American Academy of Pediatrics recommends steerable sleds, which are safer than snow discs or inner tubes (or the cafeteria trays or trash bags many adults fondly recall). And don't put more people on a sled than the manufacturer recommends, added Sinha.

As for the right age when kids can go off on their own, it depends, Mogel said.

"Each child develops at their own pace, so some children are far more mature than their older brother or sister," Mogel said. "You have to look at the quality of that child's general judgment and their definition of fun: Some prefer to break off giant icicles and study the beauty of the sun's reflection at different angles; others like to burn off energy with physically thrilling experiences."

That said, if you sense that your 9- to 11-year-old child is ready, trust him or her to venture out with a group of friends, Mogel said.

Rachel Glass knows her girls - Ella, 6, and Sophie, 4 - are too young to go out by themselves. But they do need to burn off some serious energy, so she created a snow mound on the front lawn of her Cherry Hill home a couple of weekends ago.

She can't predict when she'll feel comfortable letting them venture off unsupervised, but in the meantime, she enjoys other turns modern sledding has brought.

"With social media and Facebook, people are saying, 'We're going to be sledding at this hill at this time,' " she said. "Then everyone posts their pictures online" - kids and parents, side by side.