The plans might be secret now but they're going to have to be released before the first sod is cut. If the plans are crap, then the public is going to end up finding out. If Welsh Labour is planning to waste more than a billion pounds of taxpayer's money on a crap scheme, they're going to hear about it. We know how much the other political parties criticise them when they do anything at all, so just imagine how bad it would be if they actually had a rubbish plan. They can't railroad a scheme through the Assembly because they don't have a majority, and because their politicians want to be re-elected. If a Labour AM votes it through and the electorate find out it's all a complete waste of money, they're going to face the consequences at the next election. Transport might be an important role for the Welsh government but this scheme isn't worth losing a future election over.
With a transport scheme like this, it's fairly easy for experts to get involved and make judgements which carry a lot more weight than normal politician-speak. If they're planning on spending all of this money to run a bad service, there will be plenty of people across the engineering and governance sectors who will be happy to point out all of the flaws. I can't think of many other transport schemes which have gone ahead despite active opposition from knowledgeable sources.
- The reason it's easier to develop these extensions is partly because of the lower safety standards of light rail. Is this something we should be willing to accept? We saw what happened in Croydon. Similarly the infrastructure isn't always maintained to the same standards. Metrolink has had these issues with things failing and major disruption resulting
Light rail isn't about having lower safety standards. In some ways, safety can be different. Heavy rail trains might be more segregated, but if something does go wrong they have a harder time stopping before hitting something. Light rail systems are allowed to be, well, lighter because they're not expected to share track with fast, heavy trains. A Class 195 will be a much stronger and more expensive vehicle because it has to be able to handle a collision with a loaded freight train. A tram just needs to worry about other trams, or other road vehicles like buses and lorries. If a freight train hits a tram, then something has gone very, very wrong indeed.
Moving forward, it seems likely that new systems (such as a light rail conversion of the Valley Lines) will have higher safety requirements than before. After the Croydon incident any new light rail trains will probably need fitted with safety glass and some sort of emergency speed control. This isn't going to add that much to the cost or change the nature of light rail, so it's not really that relevant in this discussion.
It's appalling that there is apparently no money to electrify the whole of the SE Wales Metro area, Inc the lines to Vale of Glamorgan, Maesteg, Ebbw Vale, and the mainline to Bridgend & Swansea, or do any enhancements up the Marches, or build any heavy rail extensions or new openings anywhere, yet £1.5 billion (which will go up again) is available to squander on this environmentally devastating, damaging scheme.
Putting aside concerns about this specific scheme, the idea that £1.5bn might be available for this but not for normal heavy rail improvements is perfectly reasonable. Governments have to make decisions about how best to spend the money they've got. That £1.5bn could go on all sorts of different things, and the government has to find the use which will give them the best return. For the reasons I've tried to outline, in general the use of light rail technology is more cost-effective at delivering good outcomes for urban transport projects. £1.5bn on light rail might get you £2.3bn worth of benefit, while that £1.5bn on heavy rail might get you only £1.7bn.