A nearby resident said he and his wife were watching television when his wife heard a loud bang, but he reassured her it was just the train passing through the intersection.
But after getting a phone call to say there was a crash, he rushed to the scene. The traffic was "chaotic" until the attending police officer quickly took control, he said.
The man, who asked not to be named, said the car was thrown into a grass verge off the road alongside the train tracks after the impact.
A woman believed to be in her mid-20s and her young child, who managed to get themselves out of the damaged vehicle, were sitting another driver's people mover.
They managed to walk to the ambulance, the man said.
Police said the occupants of the silver Mitsubishi were taken to Tauranga Hospital by ambulance.
The resident said 200m to 300m before the rail crossing there is a clear line of sight for anyone approaching when the red flashing lights are activated, and had been working.
The crash happened as heavy rain started to fall, he said.
At least 12-14 trains a day passed through this intersection, the man said.
The train driver had been stood down and would be offered counselling, which was normal procedure after a crash, a KiwiRail spokeswoman said.
The cause of the crash was still being investigated.