Michael Birch, 44, was one of 23 people injured in the accident in East Mersea near Colchester, on 23 September.
His wife Gemma has told the BBC her husband was "very lucky to be alive".
Six people involved in the crash were taken to hospital with serious injuries. Essex Police would not reveal their current condition.
Mr Birch has so far had four operations and his wife said it was "too early" to say if he would fully recover, but he was making "good progress".
He is still being treated at the Royal London Hospital for injuries sustained after being crushed by the steam engine.
Mrs Birch described the moment she first saw him with "pipes and tubes everywhere, it was just horrible".
She was told he was "really, really poorly" but doctors were "doing all they could".
Two weeks after the crash, she said her husband was "making good progress". "They're happy with him at the minute."
Mr Birch has undergone four procedures to repair his bowel, take fragments of glass out of his body and has had reconstructive surgery on his hand.
He is conscious but "very tired - just taking each day as it comes", his wife said.
He had not really spoken about his injuries, she said, although he was aware of the extent of them.
"I don't think he's ready," she added.
Asked if her husband would be able to return to his job as a bus driver, she said: "I don't know that.
"He's quite a determined person so we'll just have to wait and see.
"It's been hard, but we're getting there."
A fundraising page set up to help Mr Birch's family has so far raised more than Â£1,200.
A 51-year-old Great Yarmouth man arrested after the collision on suspicion of causing serious injury by dangerous driving was released on police bail.

29 March 2016 Last updated at 15:44 BST
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A bus driver who was seriously hurt when a steam engine fell off a lorry into the path of his vehicle remains "really poorly", his wife has said.
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