In last month's Mt Victoria newsletter we mentioned that there were upgrades planned for the Mt Victoria tunnel, which may have some impact on our neighbourhood. In this mornings' Dominion Post, the full extent of that impact was made clear.

For those who didn't see the paper, the Wellington Tunnels Alliance is intending to spend $80 million bringing both the Mt Vic and The Terrace tunnels up to modern specifications, which means improving a whole host of infrastructure ranging from tunnel linings to earthquake strengthening and ventilation. The main reason for the work is because the tunnels don't meet modern fire standards.

However in keeping with the car-centric approach of traffic engineers, the impact of these changes on the local communities have not been well thought-through. For starters, the proposed ventilation upgrades in the main Mt Victoria tunnel will see carcinogenic diesel particulates spread over a much wider area of our neighbourhood.

The ventilation stack for the tunnel is located in the grounds of Wellington East Girls' College, and the engineers' intention seems to be to double the rate of airflow through the ventilation shaft. The exhaust from the stack is composed of vehicle fumes from cars (such as nitrous oxides and carbon monoxide) and particulates from diesel engines, which are a known carcinogen. The very fine soot-like particles are capable of embedding themselves deeply into the lungs of people breathing them, and it's this effect that most concerns health professionals. And according to the Ministry of Health, around 400 people a year die from the impact of vehicle pollution. So spreading the pollution more widely - rather than filtering it, as they do in Australia and Europe - is clearly a substandard approach.

But leaving aside the fact that more Mt Victorians will be gassed, the other key problem for local residents will be the additional traffic congestion caused by the temporary tunnel closure.

It's being reported in the DomPost that additional bus services are being contemplated to ease the load on the roading network. Yet we're already seeing regular bus congestion in Pirie Street, as the number of services exceeds the ability of the narrow one-way tunnel to accommodate them. Adding yet more buses to the mix will make things worse, not better. And we can expect an increase in illegal tunnel-running by private cars trying to circumvent congestion elsewhere, which will further exacerbate the problem.

We're even expecting other areas of the neighbourhood to be affected as cars attempt to use Palliser Road and Majoribanks Street as a shortcut. As local residents will attest, Majoribanks Street already suffers from tailbacks at peak times, and this will get worse while the tunnel is closed, forcing cars into otherwise quiet local streets such as Brougham Street and even Austin Street.

There's no really obvious solution to keeping the transport network running while the work is being done on the tunnel. However the engineers need to take a more balanced approach than their current plans seem to indicate, as Mt Victorians are unlikely to react well to having their neighbourhood turned into gridlock for a few weeks, and then gassed for a few decades.