The long-awaited tram-train link between Sheffield and Rotherham has been hit with further difficulties after planned engineering works due to be carried out this weekend have had to be rescheduled.
Works were due to be carried out on the overhead power lines in Tinsley but Stagecoach Supertram said work would instead be carried out on another part of the track.
Amy Brenndorfer, Network Rail spokeswoman said: "The same volume of works will still be carried out this weekend and this will not lead to any further delays.
"The planned work for Tinsley will be rescheduled."
The project is already running £60 million over budget and is not expected to be complete until the summer - three years later than originally planned.
It was labelled as an example of 'how not to' manage a rail project by Meg Hillier, chairperson of the public accounts committee and she said 'unrealistic costings' went unchallenged.
Tram-trains were due to begin running on street tracks and railway lines between Sheffield city centre, Rotherham and Parkgate in December 2015, but the work is more than two-and-a-half years behind schedule.
It is intended to be a pilot scheme to test the concept for possible wider roll-out across the UK to reinvigorate under-used rail lines, improve access to city centres and release capacity at mainline stations.
Modification of the national rail network has been part-funded by the Government and managed by Network Rail.
The latter's work to modify the rail network in South Yorkshire will cost £75.1 million compared with an initial estimate of £15 million when the scheme was first approved in 2012.
The PAC compared the project to Network Rail's delayed and over-budget electrification of the Great Western rail line. It recommended the government-owned company improve its ability to produce realistic cost estimates and ensure it makes appropriate allowances for risk and uncertainty.
Ms Hillier said: "This project promised great benefits for passengers and, importantly, a potential model for similar schemes in cities such as Manchester, Cardiff and Glasgow.
"Instead the reality is another rail project with all the makings of a 'how not to' seminar for senior civil servants.
"This pilot was trialling technology new to the UK, yet neither Network Rail nor the Department for Transport properly considered the high level of risk and uncertainty."
Stagecoach Supertram said the works originally planned for this weekend would be rescheduled and services would run as normal.