John Bacon

USA TODAY

The accidents are a parent's nightmare: a child airlifted to a Pittsburgh hospital after a fall from a roller coaster. Another brain damaged after falling off a Ferris wheel in Tennessee. A 10-year-old boy killed on a Kansas water slide.

The nightmares are reality and have all happened in the last four days, bringing renewed worry and call for safety reforms at amusement parks in several states across the USA.

Safety experts such as Ken Martin have called for more stringent uniform federal regulations of amusement parks. They say that in the zeal to build more thrilling rides, some amusement parks may be building in more danger. "To have fun, you don't need to necessarily be the tallest or the fastest," Martin says.

In the latest accident Thursday at a western Pennsylvania amusement park, there may be a silver lining, according to Westmoreland County officials. The child, whose age was not available, was conscious and alert after the incident at Idlewild and SoakZone park in Ligonier, about 50 miles east of Pittsburgh.

Park spokesman Jeff Croushore told WTAE-TV in Pittsburgh the incident occurred on the Rollo Coaster, a ride that dates to 1938.

"Our rides are inspected daily... safety is always our number one priority," Croushore told the TV station.

It is the third major incident at a U.S. amusement park since Sunday, when a 10-year-old boy died on a giant water slide at Schlitterbahn Waterpark in Kansas City. Caleb Schwab was riding on the "Verrückt," German for "insane," which is billed as the world's tallest water slide. The park reopened Wednesday amid an ongoing investigation. The water slide will remain closed for the season.

On Monday, three children fell more than 30 feet from a Ferris wheel when their basket overturned at the Greene County Fair in Greenville, Tenn. All were injured and Briley Reynolds, 6, remained in critical condition Thursday. The rides at the fair were being dismantled Thursday.

The ride was operated by Family Attractions Amusement, a Georgia-based firm linked to an accident three years ago at the North Carolina State Fair that injured five people, the Associated Press reported.

A 2013 study by the Nationwide Children’s Hospital, a pediatric health care and research center found that, from 1990 to 2010, 92,885 children under 18 were treated in U.S. emergency rooms for amusement ride-related injuries – or an average of 4,423 per year. More than 70% of those injuries were in the summer months of May through September, for an average of 20 injuries per day.

U.S. fixed-site amusement and theme parks – permanent sites like Disney and Six Flags parks – attract about 335 million visitors a year and water parks draw about 85 million visitors a year, according to the International Association of Amusement Parks and Attractions, or IAAPA.

Kansas park reopens after boy's water slide death

In Pennsylvania, the Idlewild park features numerous amusement rides ranging from kiddie ones to two roller coasters. Park visitors must be at least 3 feet tall to ride the Rollo Coaster, and those under 4 feet must be accompanied by an adult, the park website says.

The coaster's two trains "carry riders up and down along a wooded hillside then turn around in a swooping curve and return to the station," the park website says.

Mom: Girls injured in Ferris wheel accident improving