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The business case for light rail in Wellington stands or falls on the answer to the following question:
The available evidence shows that:
An optimal light rail design will adopt patronage-seeking characteristics and avoid patronage-limiting characteristics. Route design south of the Basin Reserve is critical to overall viability. A “string-of-pearls” design will perform better than the “split route” recommended in the Spine Study.
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Mass transit has high capital costs and cannot be justified on lightly used routes, but operating costs are low on busy routes. The most important single operating cost—bus or light rail—is employing the driver, so big savings are possible when demand is high.
Comparison between bus and light rail cost of ownership shows that light rail costs break even with buses (places/hour: standing and seated passenger-spaces available) at under 3000 pass/hr, and at 4000 pass/hr are around 75% of bus costs (Emerging Technologies for Rapid Transit, Part I page 12).
Actual capital and operating costs for Montpellier (population 384,000) in 2008 give costs per passenger boarding (How to Deliver Public Transport on Reduced Budget). It shows light rail costs per passenger are 70% of bus costs. At that date, light rail was carrying some 282,000 passengers per day.
A standard-width 63 metre light rail vehicle can carry 470 people as comfortably as a three-axle bus can carry 75, at twice the speed. This makes driver productivity about a 12-fold improvement.
To maximize ridership and make light rail viable, Wellington must focus on all-day travel, 7 days a week, with peak service to supplement the base product. Light rail needs to link dense residential areas and busy destinations, with good connections to buses and suburban trains. It needs to go to places that are busy all day, like shopping areas, the regional hospital, and airport. Avoid places where few people live, like the town belt.
Light rail is going ahead in Auckland, where the busiest bus corridor carries 86 buses per hour. In contrast, the Golden Mile in Wellington peaks at over 120 buses per hour carrying an estimated 6400 passengers per hour (almost 55 passengers per bus). Wellington has a bigger problem than Auckland, on a smaller scale.
We concluded that the existing Golden Mile route is the best place for a bus route, carrying up to about 50 bus/hr and providing a variety of services:
Bus numbers on the inner city route would be permanently cut back to about 30–50 bus/hr. Passengers using light rail would have the option of changing to a bus, or walking to their final destination from the nearest light rail stop. The existing route would flow freely, making it well-suited to passengers not wishing to walk far.
At 40 bus/hr carrying 2200 pass/hr (assuming that free-flowing routes boost ridership to 55 passengers per bus), the estimated potential light rail ridership is 4200 pass/hr — rounded to a conservative 4000 pass/hr, well over the 3000 pass/hr needed to make light rail viable. End-to-end route design is critical to realising this potential.
Can Wellington design a light rail route that delivers all-day patronage and achieves the 4000 pass/hr potential? From study of overseas light rail systems, we know that successful urban light rail systems maximize demand by following 6 principles.
A route that satisfies these principles follows. At 9km, the route is long enough to offer significant travel time savings for a wide variety of trips, including those connecting with buses and heavy rail. It forms a continuous “string of pearls” and links multiple sources of all day demand.
Te Aro Park
South of the Basin Reserve, it joins up high density residential areas and sources of all-day demand in a single route. This requires two tunnels: a double track tunnel under the airport runway and a single track tunnel under Mt Albert between the Zoo and Kilbirnie. A third tunnel under Mt Cook connecting Taranaki St and Adelaide Rd is also an option.
In the CBD, the route could run via Stout Street, Lambton Quay with a station at Midland Park, crossing to Jervois Quay with a station at Frank Kitts Park, and Taranaki Street with a station at Te Aro Park. A waterfront route would be faster, but may attract less patronage.
Service frequency would be 5–6 minutes in peak periods (capacity at least 4700 pass/hr) and 10–12 minutes off-peak. Maximum capacity (at 2½ minute frequency) would be about 10,000 pass/hr. At 40 vehicles per hour (20 in each direction), grade separation would be needed at any intersections with peak-hour traffic volume exceeding 900 vehicles per lane.
The first light rail route in a new city is rarely the last. Several extensions are possible in Wellington, including Karori; Island Bay; Kaiwharawhara (possible new ferry terminal); Johnsonville (costly because the existing line would need double-tracking) and perhaps an extension to Lincolnshire Farms. Light rail to Lower Hutt may be a better-value option than increasing capacity of heavy rail services.
The main principle is that a required change to light rail is undesirable for a short trip, because over a short distance the speed of light rail is not enough to offset transfer delays. This is the “one-stop-short” problem.
The Spine Study chose a split route for light rail. The main route took the standard present-day bus route to the Basin Reserve, then a new twin tunnel to Hataitai and Kilbirnie. A branch left the main route at the Basin Reserve and ran to Wellington Hospital and a terminus in Riddiford St. This route suppresses demand in various ways.
A split route is ill-suited for capturing demand south of the Basin Reserve. Such a route is expensive to build and operate, while delivering an inferior service — or no service — for many potential passengers.
In light of these problems, it is not surprising that the Spine Study found light rail on this route was not viable. The Spine Study light rail route is unlikely to attract the patronage needed to make light rail viable. It offers few opportunities for future patronage growth, so may not be viable for many years, if ever.
An unavoidable negative effect on patronage will be completion of Transmission Gully. Highway completion will reduce heavy rail patronage, although the effect on light rail may be minor. Most rail passengers walk from the Railway Station to their final destinations. The remaining 14% or so (data from Douglas Economics) take the bus, but about half of these (personal observation) are students going to Victoria’s Kelburn campus.
Much-improved public transport in Auckland—electrified rail and the North Shore Busway—has generated rapid patronage growth. Both services are seeing 20% annual growth, and running into capacity limits. Auckland rail in particular struggles with above-forecast overcrowding.
This indicates suppressed demand, and often happens when public transport improves. A common and widely-reported problem on new light rail systems is too few vehicles, sometimes needing costly vehicle-leasing. For example, Monpellier in France, Bergen in Norway, and Dublin in Ireland all under-estimated their initial ridership (Auckland findings).
A 20% annual growth is a doubling in under four years, so if light rail in Wellington opened in 2027, it might initially carry 4000 pass/hr, but could exceed 8000 pass/hr in 2031. If this were to happen, a five minute service would be insufficient, having a capacity of only 5600 pass/hr.
Overseas cities with well-integrated bus and light rail services routinely report twice the ridership per capita that Wellington currently experiences. Evidence from such cities shows that people value the following characteristics above all others:
An optimal light rail route in Wellington can deliver a step change in system reliability:
Light rail reliability can be designed in. Bus reliability can be progressively improved, using real-time data to identify the most important delay-points.
At worst, and likely with a suboptimal split route, light rail patronage would grow at or below the rate of population growth. Potentially, and likely with an optimal string-of-pearls route, light rail patronage would grow rapidly.