Train drivers say it's a "constant nightmare" passing through the Waikato town of Ngaruawahia, which is one of several trouble spots nationwide.
An 11-year-old girl had been playing with friends near the bridge on Great South Rd when they heard or saw a train coming towards them about 6pm on Sunday night.
She wasn't able to get out of the train's way quick enough and was fatally hit.
The Rail and Maritime Transport Union general secretary, Wayne Butson, told NZH Focus the Ngaruawahia death is an absolute tragedy.
"We've also got a locomotive engineer and a trainee who were sitting in the cab, who will be traumatised and certainly feeling the negative effects."
He says Ngaruawahia is of concern, along with several other locations throughout the country.
"The problem is ... is that when train drivers are driving trains near these spots, they get very very stressed, they start worrying and they always live with the constant nightmare that actually they may know the person being involved in this," he says.
Butson knows of a driver who once hit his wife as she crossed a level crossing.
"Most of them drive trains because they love driving trains. What they do not love is killing people."
He says the vast majority of the train drivers working in New Zealand have been involved in at least one fatality.
"I was a train driver for 20 years and unfortunately I've had numerous level crossing incidents and fatalities," he says.
"Some people say it's part of the job, I don't accept that. Anything that's preventable, we should do anything we can to stop it. We have train drivers each year who have to give up the job they love doing, simply because they end up with post-traumatic stress [disorder]."
Buston thinks the penalty framework around walking on the tracks should be revisited.
Many measures have been taken to ensure children do not climb onto a rail bridge in Ngaruawahia, but fences are pulled down and young people ignore the warnings, KiwiRail chief executive Peter Reidy says.
Higher fences, trespass notices and even a speed restriction for trains have been put in place but they don't work, Reidy says.
"Young children are accessing the track to jump off the bridge [into the river], so this [death] has been many years in the making," he told RNZ on Monday.
"Youth will use cars to pull the fencing off and even if we restrict the speeds, they climb on the trains and jump off them."
Reidy says police, the local community, council and KiwiRail will meet to discuss further measures and more education for local people about using the bridge to dive into the river.
He says another bridge is an option, but that would still be used to walk over or dive off in the same manner.
"The key, for us, is to limit the access to the railway line."
Waikato District Mayor Allan Sanson says one of the councillors lives near the scene and went down to see what he could do.
He says the sight of the grief-stricken family members was unbearable.
The 11-year-old girl's death is the first on the tracks at Ngaruawahia since 2002.