Transport for London says that around 30 per cent of buses ran during rush hour. The Unite union has a lower estimate at closer to 20 per cent.
More top news
A total of 270,000 documents is expected to be submitted to the inquiry.
In September TfL refused to renew Uber's licence on the grounds of "public safety and security implications".
Lord Kerslake said the health service could not continue "staggering along" under the current funding levels.