LRT: core of a connected rapid transit network

The team at LGWM has released a treasure trove of documents, setting out the technical advice they received from their specialist consultants. These documents give us insight into the analysis and evidence backing the LGWM conclusions. It is particularly enlightening to read the story behind the mass transit proposals, told in the MRCagney report, Public transport network integration concepts.

Light rail physically separated from other traffic

Light rail physically separated from other traffic

There is a lot to like about these proposals.

The story starts by asking exactly the right question:

What would be required to make LRT really work as the core of a connected rapid transit network for the City of Wellington?

MRCagney then sets out the principles an effective rapid transit design must satisfy:

  • An integrated ‘trunk and feeder’ network model
  • Leverage capacity, speed and reliability potential of LRT
  • Minimise bus volumes / congestion on Golden Mile
    • “Force” a shift to LRT through network improvements
  • Co-ordinate rather than compete for patronage
    • Bus routes that directly compete with the LRT corridor should be removed or reconfigured
    • Buses beyond the end of the LRT corridor should be reconfigured as high frequency feeders
  • … but avoid forced transfers close to town, or double transfers to major destinations

To satisfy these principles, MRCagney concludes that:

Transferring to LRT should be at least as fast as a direct express bus

This implies:

[we] need significantly faster LRT trunk to overcome transfer penalty

This is the key message from the report; to succeed in attracting as many riders as possible, we need to make the LRT line as fast as we practically can. We do this by designing and building what MRCagney calls a Metro Style system [emphasis in the original]:

  • 25-30km/h average speed
  • Widely spaced ‘station’ platforms
  • Little to no mixing with traffic and buses: permanent, physically separated dedicated lanes
  • Parking removal, traffic lane reduction
  • Right turn bans: LiLo [Left-in Left-out] to driveways and minor streets
  • Pre-emptive traffic signal priority

The proposed route is 10.1km one way, with 12 stations (a station about every 900 metres on average):

  1. Airport

  2. Miramar Shops

  3. Kilbirnie

  4. Zoo

  5. Newtown Shops

  6. Hospital

  7. Basin Reserve

  8. Te Aro South (Vivian Street)

  9. Te Aro North (Courtenay Place)

  10. Civic Centre

  11. Queens Wharf

  12. Wellington Railway Station

MRCagney proposes changes to the bus network to remove directly competing bus routes and reconfigure other routes to act as feeders to LRT, while avoiding a need for double transfers. In any other city, this ‘trunk and feeder’ network model would be squarely in the mainstream and uncontroversial. However, as a result of their recent bad experiences with the bus network redesign, people in Wellington rightly mistrust transfers. Consequently, LGWM may encounter some serious criticism; in this case, the critics will be wrong.

The proposed light rail route is not the most direct route from A to B. To make up for this, the street layout needs to be designed for maximum speed. The design calls for running light rail in the middle of the street, which reduces interactions with general traffic and allows for the highest possible cruising speed. We need to aim for an average speed at the upper end of the quoted range, closer to 30km/h than to 25km/h.

Here is a typical street cross-section, showing a station in the middle of the street.

Indicative street cross-section on Adelaide Road

Indicative street cross-section on Adelaide Road

So far, so good. Unfortunately, things go a bit pear-shaped for rapid transit at the Basin Reserve. Here is the LGWM Basin Reserve preferred approach (the dotted red line connecting Taranaki St and Adelaide Rd is the recommended rapid transit route):

Preferred approach for evaluation included in the 2018 Recommended Programme of Investment

Preferred approach for evaluation included in the 2018 Recommended Programme of Investment

The problem facing LGWM is that they need to avoid having rapid transit cross SH1 at grade, which would introduce major delays during busy periods. But this proposed solution has serious shortcomings as a concept for rapid transit:

  • It makes four right-angle turns in 300 metres or so, which will slow things down more than a bit

  • It runs through the National War Memorial, a pedestrian area, which will slow things down even more

The alternative, that FIT and others have proposed, is a 2-lane rapid transit tunnel under Mt Cook, emerging on Douglas St just south of the Basin. The other end of the tunnel depends on what we decide to do with SH1:

  1. The first and preferred option is to run SH1 under Taranaki St, rapid transit crosses at grade and enters the tunnel south of SH1. Trenching SH1 through Te Aro would create massive opportunities for the area.

  2. The alternative is for SH1 to cross Taranaki St at grade, rapid transit enters the tunnel north of and goes under SH1.

There is a brief discussion in the LGWM documents about why rapid transit follows the path it does. Was it a cost-cutting exercise to avoid a rapid transit tunnel? If so, are we spoiling the ship for a halfpennyworth of tar? This investment will shape the city for a century; should we not spend a bit more to do it right the first time? Here is what the LGWM team says (page 5):

The Memorial Park/Tasman St option was identified as the current preferred route over the Mt Cook tunnel option due to a combination of factors:

  • Covers more of Adelaide Road — urban redevelopment potential
  • Uses existing grade separation to avoid conflict with SH1
  • Provides better access to schools to the east of the Basin
  • Likely to cost the least and be easiest to deliver.

Deliverability challenges in relation to the [Memorial Park/Tasman St] option were acknowledged in relation to tight bends, potential impact on Mt Cook School and a steep gradient for a short section — but there were equally significant deliverability issues with all other options.

Apart from the Basin problem, the proposal ticks all the right boxes and we need to get behind it and get on with it; fine words butter no parsnips. As LGWM moves to the refine and design stage, there are some traps to watch out for:

  • resist the temptation to add more stations; just say no

  • physically separate the rapid transit lanes from general traffic; paint may be cheap but it is not fit for the purpose

  • find ways to speed it up and don’t do anything to slow it down; just don’t

Let’s do this, in full, by 2030.