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It was going to mean the worst-polluting cars, lorries and buses would be banned from the city centre, with a two-year grace period leading to enforcement from June 2024.
But instead the opposition parties combined to defeat the SNP-Labour administration on this flagship policy.
It's not that the Tories, Greens and Liberal Democrats all agree in their criticisms of the proposed scheme. They each have their own angle on why it's not the right answer to the acknowledged problem of pollution which translates into poorer health.
But they all wanted changes to the scheme, so when it came to the final vote at Tuesday's meeting they united in backing the Green amendment rather than the motion to approve the proposals.
So what happens now?
The decision came as a shock to the administration and in the immediate aftermath there was uncertainty over exactly how it left them and what the next step would be.
A delay now seems inevitable – and Tory group leader Iain Whyte has predicted it could be after the council elections next May before a revised scheme comes back for councillors to approve.
The process before an LEZ can be introduced is in any case a lengthy one – after council approval there is a further 28-day period for formal objections, which could lead to some kind of inquiry, which may or may not involve public hearings, and then it has to be approved by the Scottish Government.
Council officials will have to look again at the proposals in line with the Green amendment, which urged more attention to greenhouse gases as well as the nitrous oxides emissions by which the LEZ is measured, and also called for the boundary and the grace period to be changed – but without specifying how.
That could revive the question of a second city-wide zone in addition to the city-centre one. That was part of the original plan, but it was dropped on the basis the standards set for the city centre will have a knock-on effect throughout the city and the extra benefit of city-wide restrictions could not be justified in economic terms.
Dropping the city-wide zone left two of the worst-polluted streets in Scotland – Queensferry Road and St John's Road, Corstorphine – outside the LEZ, which has drawn criticism, not least from Corstorphine Community Council, who said they would lodge a formal objection over it.
Changing the boundary might also mean more minor changes to the lines of the 1.2 square mile area identified for the city-centre zone. The concern voiced by critics is that vehicles which do not meet the required emission standards will cause more pollution in the streets just outside the zone as they divert around it.
However, if the grace period is shortened that could arguably allow the scheme to come into full effect, with enforcement, as planned in 2024.
But a lot must happen before then.