Ask Phoebe: Engineers' tunnel vision laudable

The numbers on SH1 exits were set in 2005 in anticipation of the 4km trim the toll road would make. Photo / Kenny Rodger

If the tunnel north of Orewa has taken 4km off the length of SH1, does that mean that all the motorway exit numbers south of Orewa will need to be changed? The numbers are surely the distance from Cape Reinga. And what about all the kilometre measures alongside the highway, not to mention the identification numbers on bridges? Ken Bray, Pakuranga.

Last things first. As I reported earlier this month, the kilometre measures will be updated once the new distances have been mapped against the existing signs. I don't know about the bridges.

But when those clever old engineers at the Transport Agency were planning the exit numbering system, they took into account the toll road and that it would be operating by 2010, and adjusted the numbering accordingly. Thus we have actually been driving 4km further than we thought since 2005, when the exit numbering was introduced, but not any more. And in the greater scheme of things, given that it is almost 170km from Whangarei to Auckland, 4km isn't so much.

As you say, numbering on SH1 begins at Cape Reinga, the Northwestern Motorway (SH16) begins at the Port, and the Southwestern Motorway (SH20) begins at its link with SH1.

Stuart Rattenbury of Royal Oak reckons there is a better scheme for labelling exits. It has 26 characters, which can be arranged in groups of random order and length to form unique labels, such as Penrose, Papakura and so on.

NZTA justifies its use of numbering by saying it is a system that has been used successfully in countries such as Australia, the US and Britain, and that it means visitors don't have to try and remember all those funny names we insist on using. And apparently the numbering system helps emergency services locate and respond to incidents quickly and efficiently.

When coming from the North Shore, using the Port exit to get to the big new university carpark or Auckland City Hospital, I always wonder why there are no signs to tell one to move to the left lane and turn off at the Wellesley exit. If one knows this, it is an easy matter to then turn right at the intersection and follow the signs. However for occasional users of the university area, for example visiting the Maidment Theatre, it is very confusing, and all too easy to get lost by overshooting the exit. Could some better signs be erected please? Nancye Bourke, North Shore.

The Transport Agency agrees, Nancye. There should be a sign here that says "Hospital Grafton University This Exit". And there was. But it blew off its pole. It'll be back next week.

If you spot anything on the motorway network in Auckland that needs attention, call NZTA on (09) 520-0200.

Last month I asked for advice on the location of town centres, for the purpose of measuring distances between towns.

One of the boffins at the Transport Agency has supplied the following:

More often than not it is the traffic and engineering section of the road controlling authority (the local council) who decides the location of the town centre.

The town centre is identified nominally as the central business district and can either be the post office or district council office if this is in the central business area, or a major shopping district such as Manukau City Centre.

Council staff or the Transport Agency traffic engineering sections keep a close eye on any changes that affect traffic operation and traffic engineering services, such as sign renewal and maintenance.