Avon and Somerset Police closed the Lower Bristol Road in Bath at Rackfield Place outside the First depot after the crash at 03:00 GMT.
The A36 road closure, which was lifted at 14:00 GMT, had caused disruption and delays to commuters and bus services during rush hour.
Investigations are under way into how the collision happened.
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First said that while parts of its services had resumed a normal schedule, it would take a few hours for all services to return to normal.
Managing director James Freeman said: "We are hoping we will have a full service running in time for the evening commute.
"We would like to thank the public for their support and understanding and staff for going beyond their call of duty to help manage the situation and recovery."

Alexander Reid repeatedly told Department of Work and Pensions staff in application forms and at interviews that he was single.
But in reality he was living with his wife Kathleen Reid, despite having claimed to be separated.
Reid was found guilty following a trial at Dundee Sheriff Court.
The 59-year-old, from Dundee, had denied a charge under the Social Security Administration Act that he fraudulently claimed employment support allowance and income support totalling £39,808.
Defence solicitor John Boyle asked that Reid be spared jail and given a community payback order as an alternative to a prison sentence.
Sheriff Tom Hughes told Reid: "Because of the sum of money involved a custodial sentence is the only option."

Three masked men, two armed with handguns, forced their way into the property in Glenfearna Gardens in the Lagmore estate at 22:45 BST on Friday.
They threatened the women, aged 81, 49, and 25, and tied up the 49-year-old during the robbery.
The gang left in a small silver vehicle with a substantial sum of cash.
One of the women, Saoirse Joyce, said it was a traumatising experience.
"They barged into my room - two masked men that I could see," she said.
"I just jumped up to the window and pushed the window open and shouted out help, but one of them trailed me down by the hair onto the ground and said to the other one 'hold her there'.
"He pointed a gun to my head and I couldn't move and all I kept saying was 'my granny, my granny',".
Det Const Fiona Mills said: "This was a despicable act perpetrated against three generations of the one family.
"All of these women have been left understandably extremely shaken and upset by the ordeal."
Police appealed for anyone with information to contact them.
A woman has died after her car crashed outside a bus depot trapping 150 buses inside.
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A man who fraudulently claimed nearly £40,000 in benefits over the course of almost 11 years has been jailed for 18 months.
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Three generations of women from the same family have been threatened during an armed robbery at a house in west Belfast.