The brother of the driver involved in a NSW demolition derby crash that injured 13 people has called for improved spectator safety at such events.

The accident at the Walcha Motorcycle Rally occurred late on Saturday when 27-year-old speedway car driver Steven Taylor crashed through a fence and into a mobile grandstand.

Fourteen ambulances and four helicopters responded to the incident at the Walcha showgrounds, about 90 kilometres from Tamworth in NSW New England region. Two spectators were flown to Newcastle’s John Hunter Hospital in a critical condition.

NSW Police said they had been told that the driver was involved in an on-track collision immediately before his vehicle crashed through the fence.

In a video posted on social media after the accident, Steven Taylor’s brother Blake suggested Steven had blacked out with his foot “wedged hard on the accelerator” after hitting a car in the middle of the field.

“It’s still totally hard to believe… just to personally see the damage”, he said of witnessing the crash.

“We’re here to put a show on, not hurt people.”

He told 10News+ on Sunday night that his brother didn’t remember the accident.

Blake also said there was nothing to stop the car once it was out of control, noting that while logs were placed in the middle of the field during a previous derby, “this year they had witches’ hats”.

In further Facebook posts on Monday, Blake urged that safety at such events be improved.

He shared a post from a fellow driver who said he didn’t know if he would like to drive in a ring again where crowds weren’t protected, adding: “As a derby community we need to work together and make sure this will never happen again.”

A hospital spokesman said on Sunday that the condition of the two men who were critically injured in the crash had improved to serious but stable.

Steven Taylor was among 11 other victims aged 20 to 75 who were transported to hospitals in Armidale, Tamworth and Walcha. He was released on Sunday.

Walcha Mayor Eric Noakes said it was amazing how local communities “banded together in these episodes”, with a nurse stepping up to triage those injured.

“It’s lucky we’ve got great ambulance and SES and fire (services) in Walcha,” he told 2GB radio on Monday.

Federal MP for New England Barnaby Joyce praised “all the off-duty nurses and first responders who immediately dropped everything to help the injured in the storm” at the event.

“Such a sad end to such a great event,” Joyce posted on Facebook.

Police said their investigations into the crash continue.

In addition to the demolition derby, the annual rally features a motorcycle street procession, barrel racing, a show and shine and postie bike events.

Noakes earlier described the crash as a “freak accident”, but said the event would face renewed scrutiny by the council.

“It’s been a five-year event but things like this – we’ll certainly reassess our position,” he said.

“I’m only the mayor and don’t understand a lot of what sits behind reassessing it and our risk analysis. That’ll be something we’ll look at.”

–with AAP