To push boundaries

There were just five stops when the North-South Line was first introduced in 1987, running from Yio Chu Kang to Toa Payoh.

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Up until a year before that, Mr Yeo, then 29 and employed by the Mass Rapid Transit Corporation (later renamed as SMRT) as a railway master, had no idea what the trains would even look like.

Training, which took one and a half years, was a mix of theory and imagination. "We were trained on all the technicalities, but we'd never actually seen the train before," he recalls.

Mr Yeo had swapped a steady job as a chief draftsman at an architecture firm for a leap into uncharted waters.

Was he worried about job stability?

"No, it was a new industry; a sunrise industry," he says. His sons were young at the time, aged three and one, and he made the decision with the support of his wife, a homemaker. "I wanted to keep learning new technologies."