Despite the dangers of leaving a moving vehicle before it has reached the stop, Edinburgh councillors did just that yesterday in a desperate attempt to salvage something from the disastrous trams project.

By opting to end the line from the airport at Haymarket, their intention is clear enough: they hope to rescue something from the money already spent and keep the additional amount they need to borrow well below the £231 million required to take the line to St Andrew Square in the city centre.

Only a week away from “drop dead day” of September 1, when the main contractor, Bilfinger Berger, will halt all work and begin proceedings for the payment of cancellation costs, the vote raises further uncertainty. It is not known whether the company will agree to the truncated scheme. There is a question over its profitability, with the report by council officials projecting that if the line terminated at Haymarket it would require a subsidy of between £3m and £4m a year. And the clock is ticking.

Opting for the halfway house of Haymarket appears to be a pragmatic solution but it requires the careful scrutiny that has been so disgracefully missing from this project since the beginning. In July councillors supported taking the line to St Andrew Square. Last week a report from council officials showed the cost of the £231m required would be £15m over 30 years. Their recommendation was for councillors to approve the St Andrew Square option despite this pushing the total cost of the project to £1 billion -- more than twice the original amount. As if this were not bad enough, as The Herald revealed, the calculations did not take into account a further financial shortfall of £90m because there is no agreement from Transport Scotland to extend the concessionary fares scheme to trams despite a projection on the business case that around 20% of passengers would be eligible for the scheme.

Given the continuing runaway costs, cold feet on the part of councillors was entirely understandable. Saddling the citizens of Edinburgh with the cost of repayment for a generation would have been unthinkable were it not for the hundreds of millions that have already been thrown at the project and the serious disruption to many businesses along the route.

Unpalatable as the choices facing the elected members yesterday undoubtedly were, they can expect no sympathy from their constituents who are likely to register their disgust at next year’s council elections. Their predicament is largely due to failing in their duty as ultimate overseers of the project. Although management was devolved, disastrously as it turned out, to the arm’s-length body, Transport Initiatives Edinburgh (Tie), it remained the responsibility of the council members to scrutinise progress and costs.

The Edinburgh trams fiasco bears uncomfortable parallels with that other ambitious building project which was riven with soaring costs, delays and disputes, Enric Miralles’s Scottish Parliament building at Holyrood. Despite real problems (as there have been with the trams) it was rescued by a new regime of capping costs and time penalites. If trams are ever to run in Edinburgh, the new agreement with the contractor must be one which prevents any further escalation of costs and puts this nightmare project firmly back on track.

The evidence from tram systems in other cities is that even where there has been considerable opposition because of the high cost and where delays have resulted in lengthy disruption to travel and business, the advantages are soon recognised.

In the case of Holyrood, there is now considerable delight in the soaring spaces of Scotland’s Parliament. The degree of mismanagement of the trams project has been such that it will take decades before they have any prospect of becoming a source of civic pride.

The inquiry by Lord Fraser into the contractual and budgetary failures over Holyrood resulted in a template for overseeing any similar construction project in the future.

It is important to uncover why this project has been such a shambles. Alex Salmond has already indicated that he would be in favour of a public inquiry once the council has decided whether to go ahead with the scheme. Assuming agreement can now be reached between the council and the contractor on the airport to Haymarket line, and assuming that borrowing is available despite the projected losses on the truncated route and the proposal goes ahead, that will now happen.

There should be a public inquiry. Audit Scotland has already taken the highly unusual step of reviewing the trams project while it was still alive. As a result it recommended the Scottish Government should become more involved through making the expertise of Transport Scotland available. This begs the question of whether local authorities are the appropriate bodies to commission and oversee major infrastructure projects of which they have no previous experience and where expert knowledge is required.

Edinburgh could have drawn on the experience of other cities which have recently built tram systems. Nottingham’s experience in dealing with utilities, for example, might have avoided some of the considerable problems with underground infrastructure in Edinburgh.

It is time to draw a line under the Edinburgh tram disaster and move on, hopefully as far as Haymarket. But the lessons must be learned. Risk assessments, contingency costings and watertight contracts have all been missing. But most woeful of all is the absence of civic responsibility in the city chambers.