With the RBA mentioned, it seems reasonable to look to federal guidelines. The Department of Finance Handbook of Cost Benefit Analysis identifies the long-term Treasury bond rate as the appropriate discount factor for estimating the costs and benefits of risk-free public investment projects. However it indicates that where there is uncertainty, the discount rate should be increased.

Adjustments should also be made if the prospective benefits favour only part of the community, or if there are alternative beneficial projects that must be forgone to enable funding.

The long-term Treasury bond rate is currently low in historic terms – around 3per cent nominal interest. However some would argue that, despite light rail's guaranteed right of way, the project's projected benefits are by no means risk-free, given other less predictable factors.

They also see a disproportionate benefit to Gungahlin residents, and significant social opportunity cost in forgoing targeted expenditure on say, hospital and community health projects (yielding dollar-quantifiable savings in life years) and schools (increasing the value of human capital).

These considerations point to lower overall benefits, and suggest a higher discount rate is more appropriate for the light rail project.

Paul Feldman, Macquarie

Four letters in Sunday's (April 17) edition of The Canberra Times probably tell the story of light rail in Canberra. Two are strongly against it, a third thinks light rail is a good idea but the current proposal is misguided and needs major change, while the fourth bleats plaintively that we ought to adjust the interest rates in the business case for the tram so that it can get its head above water.

Also interesting was the visit by one of our Liberal MLAs to the Hawker shops recently. The member had a board up where people had the chance to put a tab to show which of perhaps 10 issues listed was the most important to them. When I looked at it, health was on top with 57 tabs, "stop light rail" was next with 48, and "build light rail" had 16.

So, light rail was the most important issue for people in the area and, even taking into account this was a Liberal member, people are strongly opposed.

Andrew Barr should be worried.

Stan Marks, Hawker

Kevin Connor's letter on alternative routes for the light rail makes sense and would add a new vibrancy to our city.

However I would propose extending the northern arm to EPIC. A large, free "park and ride" car park could be built at EPIC, providing a genuine solution to easing the traffic chaos on key city access points from the north that the rail project is meant to address.

It would also allow easy tourist access to and from the racecourse and EPIC, which now hosts a growing number of grey nomad campers each week.

Jim Stewart, Palmerston

I wish to reply to the acerbic comments by James Allan (Letters, April 17).

First, drug problems are never an either/or situation – they must involve health and legal perspectives. And to bracket Portugal and Sweden for drug policies and their outcomes is misleading. Portugal, which was ranked No.1 in the EU for use of narcotics-related drugs in 1999 had to do something, so they legalised illicit drugs. Sweden dumped the idea of legalising drugs nearly 30 years ago.

In 2007 the United Nations Office on Drugs and Crime ranked 180 nations in order of the severity of their drug problem, 180 being the best, and one the worst. Sweden came in at 168, Portugal's ranking was uncertain because of insufficient data.

Australia was No.5.

The 2015 European Drug Report for prevalence of drug use records Portugal as "insufficient data available".

Colliss Parrett, Barton

David Koch is right (CT, April 17), people flock to the redeveloped Adelaide Oval for a football match every weekend of the AFL season and for first-class cricket in the summer. If the Manuka oval redevelopment proceeds, does that mean we will get the same outcome?

Thought not. All we'll get is more apartments, more retail and more restaurants.

Ho hum.

Graeme Rankin, Holder

$800m for hot showers at Manuka Oval! I think a few of us locals would kick in to fix the showers then no need for a massive redevelopment.

Nick Swain, Barton

I would like to comment on the article (Sunday CT, April 17) by Jill Stark with Adam Gartrell.

The heading was inaccurate. Members of the ACL are not anti-gay. We respect all people, but do not share the same philosophies as the LGBTI people in our society.

The Victorian Gender & Sexuality Commissioner, Rowena Allen, states that ACL aim to deny the rights of these people. We are denied the right to state our views, particularly our belief that marriage is between a man and a woman, and that children have the right to their biological parents.

There are many instances in other countries where people holding the views we share are heavily penalised.

I do not consider that a characteristic of a democratic society.

Moya Homan, Greenway

I wouldn't like your readers to be misled by Dana Olejniczak's claim in The Canberra Times (April 16) in relation to the recent outcry in Poland to tighten its law against abortion.

Mrs Olejniczak suggests any such tightening would place at risk the lives of mothers with ectopic pregnancies such as she once suffered. She warned that under the new law, yet to be drafted, "a woman would be forced to continue such a pregnancy until complications became severe enough that her life was 'directly' in danger".

This is erroneous information. An ectopic pregnancy causes a surgical emergency requiring immediate intervention, otherwise the woman will die and so will her baby.

An ectopic pregnancy, by its very nature, is doomed to burst the fallopian tube, causing the baby to die and the woman to bleed to death. I know this because I have had two ectopic pregnancies myself.

Polish doctors have always and will continue to intervene in ectopic pregnancies, as did my doctors.

Mrs Pascale Cotterill, Latrobe, Tasmania

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