Wellington Transport: Spine Study Solutions?
Spine Study Solutions?
June 25, 2013
A quality busway on Wellington’s Spine Route will be trickier and more costly than the Spine Study suggests (see earlier piece). If a busway proves unacceptable there are good alternatives.
Bus priority remains a good alternative if it is given enough space: 60 buses an hour (each way) on two lanes, or 120 buses an hour on four lanes. That would probably be two different routes. The Spine Study has already done this for bus priority east of Elizabeth Street. Doing the same thing through the city would be a good option.
The other alternative is light rail: a tramway. Here the problems are cost and interchanges. Costs have been inflated by route duplication and a pointless tunnel. A new costing problem is 22 trams, when a simple speed-distance-frequency calculation suggests that 8–10 will be enough, plus a couple of spares. The difference is about $40 million. Does this mean that the Spine Study has allowed for a five minute service on both legs of the tram route, a tram every two and a half minutes on the Golden Mile?
It looks as if a reasonable tramway cost is about $300 million, say $50 million a kilometre, in reasonable alignment with other systems. That is down from $940 million in the Spine Study, much more comparable with $200 million for a badly under-costed busway. Deciding which is the better still needs more work.
A suggested tram route past the critical ‘pinch-point’ in the Old Bank area is down Lambton Quay, narrowing to single track for the narrowest section and crossing Willis Street into a double-tracked Willeston Street. Delays would be minimal with a five minute timetable (see photo). Two advantages of this layout are:
• Hunter and Willis Streets are kept clear for
buses, general traffic or both.
• Trams can avoid Willis Street, which is probably impractical for a tramway: too many underground services.
The suggested route could continue through Te Aro to Wallace Street and Wellington Hospital. This avoids Courtenay Place (there will be buses going that way) but is better aligned with Wellington City Council’s ‘Growth Spine’ of inner city housing. An even better option would be King Street, but needing land purchases at the north end.
The growth spine is estimated to attract 18 000 new residents within 20 years but, oddly there has been no sign of residential density studies. Experience overseas suggests that many existing and most new residents would use a good-quality, well-aligned public transport spine. New residents could generate almost enough new trips to justify light rail, but NZTA modelling methods are too rigid to show these benefits.
A tram carrying 250 people—more than are carried by the cars in a one-kilometre traffic queue—only needs 10–15 seconds of green time at traffic signals. This justifies tram priority and helps to make trams fast. Brief waits at stops also make for fast trips. One manufacturer claimed 120 passengers boarding in ten seconds. Fast, reliable trips make public transport competitive, attract patronage and relieve congestion.
A quality system, whether tramway or busway, needs good interchanges. Trams are especially vulnerable to poor interchange design because passengers must change where the tracks end.
The Spine Study has allowed a huge “boarding and transfer penalty” of an average 15 minutes (July 2012 data, no final figure available). This suggests a 10% probability of waiting perhaps 20–30 minutes, long enough for a passenger to walk the Golden Mile. No wonder trams perform badly in the Spine Study, with some 90% of Miramar and Island Bay passengers having to transfer. Best practice is a two-minute transfer, 95% reliable, and an equally reliable five minutes is common.
Quality transfers need five steps. First, a quality busway or tramway. Either will be much faster and more reliable than the existing buses. At peak hours the saving is 7 minutes from the Railway Station to Wellington Hospital, or 11 minutes to Kilbirnie (by Hataitai, Spine Study Figs 6 & 7).
Second, interchanges must minimize the one-stop-short problem. Ideally, no passengers should lose more time transferring than they gain on the faster spine route. Again ideally, no passengers should have to transfer while close to the start or end of their trip.
A very bad example of the one-stop-short problem is in the Spine Study. A tramway or busway would stop at the Hospital, in the middle of the road, then presumably run on to an interchange at Newtown (unclear in the sections but suggested by Table 13 in the Spine Study). The cross-section of Newtown shows only a single tram platform beside a single-track stub, with no space for buses to stop. Where is the interchange? Why isn’t it where interchanging passengers will most want to be, Wellington Hospital? Bizarrely, the busway option uses the same layout as the tramway: reversible buses?
Third, some carefully-chosen bus routes must continue running through the central area, mainly for passenger groups who:
• would otherwise have to transfer
• travel to or from inner-city destinations away from the spine route
• live in inner suburbs and would be worse off if they had to transfer in mid-city.
There is a balance needed here. Too many buses in the central city will draw passengers away from the spine route, too few buses will create too many transfer problems. The balance will need careful modelling. The outcome will inform final choices, favouring a tramway if the transfer delays can be managed adequately.
Fourth, quality interchanges will themselves promote better timekeeping and faster transfers, as well as shorter waits elsewhere.
• A spine route
service every five minutes.
• More reliable inner-city buses because the bus route is congestion-free.
• Much more reliable suburban buses because the inner city route is congestion-free or avoided; many routes terminate at the interchanges.
• ‘Pulsed’ transfers at Kilbirnie and Wellington Hospital. Buses are timed to arrive before the spine service and leave after it.
• No services leave early.
Fifth, set up a programme of continuous improvement. The aim is progressively identifying and eliminating passenger delays, system-wide. A common european adjunct is summer and winter timetables; slight variations are useful (think weekend evenings), and the switch-over is a convenient hook for introducing the latest revisions.