Steven Dawson drove his McGill's coach into the rear of a car in Glasgow's Bridge Street.
Police tracked him down and he was breath tested a short time later after returning to his depot in Barrhead, East Renfrewshire.
He gave a reading of 136 microgrammes per 100ml of breath. The legal limit is 35mg.
Dawson told officers he had started drinking before starting his shift that morning.
Dawson, 52, of Glasgow, was arrested on Friday and held in the cells over the weekend to make a appearance at Paisley Sheriff Court yesterday.
Sheriff David Pender immediately banned him from driving and called for reports to be prepared.
The court was told that Dawson had crashed his bus into a car being driven by Jim Carnwath in the Bridge Street area of the city on March 8.
He had then driven back to the McGill's depot in Muriel Street, Barrhead, where a person who was concerned about what had happened and the strong smell of alcohol from his breath contacted police.
In court, he admitted driving the vehicle in Bridge Street, Glasgow, and Muriel Street, Barrhead, on the day in question while he was almost four times over the legal drink-drive limit.
He had also been charged with driving without due care and attention in Bridge Street, Glasgow, while carrying passengers onboard his bus and colliding with the rear of the other vehicle, causing damage to both.
When he denied that particular charge, the Crown accepted his plea.
Sheriff Pender heard that there had been 10 passengers onboard the bus at the time of the accident.
Depute fiscal Annette Ward said: "One of the other parties detected a strong smell of alcohol from the accused and contacted police.
"When officers spoke to him, he said 'I've made a mistake. I was drinking this morning'."
Defence agent John Gardner said there were underlying issues which required to be addressed.
Sheriff Pender said that before he could begin to consider sentencing options, and due to the serious nature of the charge, he would require a detailed background profile.
Deferring sentence until April 8 and calling for reports to be prepared, he imposed interim disqualification and released the accused on bail.
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