Matt Lowrie: We can't fix Auckland's traffic jams with more roads

Auckland shouldn't throw money at projects that are just about providing a little bit of extra capacity at peak times but sit under-used the other 20 hours of the day.

On Saturday, a single crash near the Central Motorway Junction in Auckland left much of the city's motorway network gridlocked for the afternoon. Many Aucklanders are askng why the impact was so large and what can be done to prevent it from happening again.

The unfortunate reality is that crashes and gridlock are an inevitable part of car-based transport systems. We can't fix that by building wider motorways - all that will do is encourage more driving and thus increase the number of people sitting frustratedly in traffic. What we can do is build a transport system that minimises the number of people affected by giving them the option to travel congestion-free by bus, train, ferry, or bicycle.

Before I go into that, it's worth covering off some of the reasons the incident on Saturday was so bad. The crash happened on the Harbour Bridge, which is one of the busiest sections of road in the country - only Auckland's Southern motorway between Greenlane and Grafton carries more cars. It also happens to be one of the busiest times of the year, with events, Christmas shopping and sunny weather all contributing towards a lot of people being out and about.

Furthermore, the location of the crash was close to the Central Motorway Junction. As traffic on this busy section of road quickly backed up it flowed back through the CMJ and at that point it started impacting not only those who were travelling to the North Shore but to other destinations such as the city centre or to West Auckland too.

As a result of the chaos we've quickly seen calls from a number of people for an additional harbour crossing to be built. In addition the New Zealand Transport Agency said the completion of upgrades to North-Western motorway and the Waterview tunnels would help. Yet observing of the effects of Saturday highlighted these projects are likely to have a limited impact.

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As people flooded to the North-Western motorway to take the longer way over the harbour, that route too quickly filled up and it too took many hours to clear. Some of that congestion may have been due to drivers checking out the continuous 12km of roadworks being undertaken however the real issue is the route isn't designed to carry that many vehicles. The same fate would have befallen an additional harbour crossing as too many drivers tried to funnel into a tunnel.

Auckland needs smarter investment in infrastructure to help keep the city moving. We know that we only have limited budgets and there's even the possibility of tolls on the city's motorways. As such we need to be mindful that we're not throwing money away on projects that are just about providing a little bit of extra capacity at peak times but are under-used the other 20 hours of the day. No city in the world has managed to build its way out of congestion by building more roads.

Traffic build-up following Saturday's crash on Auckland's Harbour Bridge. Photo / Jason Dorday

With fewer vehicles travelling across the Harbour Bridge every day than there was a decade ago an additional harbour crossing would definitely fall into this category. Moreover it comes with a hefty price tag with some estimates putting it over $5 billion and that doesn't include new or wider motorways on either side of the harbour to support it. Unsurprisingly the last business case for a new harbour crossing was appallingly bad, returning just 20c for every dollar invested.

A resilient transport system should definitely be the aim of our transport agencies, but duplicating Auckland's motorways at great expense will not provide it. Fortunately, we have proven, albeit incomplete, examples of what's needed to provide that resiliency and we can once again look to the Harbour Bridge to see it in action.

The completion of the Northern Busway in 2008 has already had a dramatic impact in how people from the North Shore cross the harbour on weekdays. An NZTA report highlighted that in 2004 before the busway existed around 18 per cent of people who crossed the Harbour Bridge did so on a bus. By 2012 this figure was up to 40 per cent, as the busway provides a frequent and congestion free alternative to driving a car. According to NZTA's traffic monitoring data, buses are often able to reach the city centre from Albany in half the time of those still sitting in their cars. This is in spite of the fact that there is still no dedicated busway over the Harbour Bridge.

The busway and our rapidly improving rail network are the start of Auckland's future Rapid Transit Network (RTN).

If we invest in a high-quality RTN with the City Rail Link at its heart, Aucklanders will use it. Even with the current incomplete network, Auckland Transport's patronage data shows that trips taken on the RTN in the 12 months to October are up a staggering 17 per cent on the same time last year. This isn't surprising as dedicated public transport routes have been the key in making public transport more successful in cities all around the world for well over a century. If services on these rapid transit systems are fast, frequent and reliable then people will flock to them.

Many cities are now rushing to install or expand rapid transit systems as well as invest in dedicated walking and cycling routes in a bid to tackle congestion. By themselves these high quality alternatives to driving won't solve congestion but when implemented properly what they will do is allow people to opt out of congestion.

A network of busways and rail lines across the city - like we've suggested in our Congestion Free Network - would do this and do so within the city's existing transport budget.

Matt Lowrie writes on transport issues at transportblog.co.nz