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Sustainable Transit Design: Accomplishing More by Building Less

Aug 26, 2011
Sustainable Transit Design: Accomplishing More by Building Less

By Catherine Calvert, Director of Community Sustainability,VIA Architecture
Photo: Canada Line, credit Ed White 

There is a common misconception in the design of large infrastructure projects like transit systems that the inclusion of sustainable design strategies is an “add-on” that increases project cost.  In our experience, sustainable design strategies are actually an effective means of: 1) Bringing Value to the project; and 2) Reducing Risk to the transit agency.

Good sustainable design is actually a form of radical common sense that can challenge some of the assumptions that accompany current transit design principles.  Using a combination of critical thinking and creativity, the integrated design process examines each component of a transit system to determine if each is necessary (rather than expected), and if each is able to serve more than one function.  In Permaculture terminology, this is known as “stacking”, and is the way that natural systems find high levels of efficiency by having each element serve many needs simultaneously.  This often means that more can be accomplished by actually building less.

In terms of Risk Reduction, current approaches to risk management tend to focus on issues that may occur in the period from Design through Commencement of Service – cost escalation, time escalation, and disruptions to the delivery process.  However, unlike other types of commercial development, transit agencies build their facilities to have an ultimate design life of 100 years or more, with capability for 50 years of continuous operation before refurbishment is necessary.  Far greater risks exist that are associated with the lifetime of the system, many of which can be mitigated using sustainable design strategies:

Lifetime risk
Sustainable design response
Cost and availability of electric power in the region
Design for reduced energy consumption and energy recovery
Wear and tear on transit facilities
Specifying for durability
Climate change impacts
Design for extreme weather events
Ridership meeting projected levels
Creating appealing, people-oriented facilities

 

Sustainable design therefore brings long-term Value on three levels:  to the Project, to the System, and to the Community.  To the Project, this means potential reductions in capital cost by finding synergies through the integrated design process.  To the System, it means bringing long-term value through energy savings, reducing life cycle cost, and using good design to attract ridership.  And to the Community, it means supporting public health by encouraging transit ridership, enhancing environmental quality, and providing mobility options that are integrated with public spaces.

In our transit design work, we have explored many opportunities to find “stacking” synergies.  Here are some examples of this philosophical approach:

Vertical Circulation:

For underground or elevated stations, it is common practice in transit design to include a combination of stairs, elevators, and escalators to provide vertical access to street level.  Elevators are essential for those with disabilities, or for the convenience of travellers with strollers or luggage.  Stairs are also essential, but escalators are worth reconsideration in some situations where lower ridership is anticipated.

From a functional perspective, escalators have the advantage of moving large numbers of passengers quickly and efficiently, but strictly speaking their function is redundant to that of stairs and elevators.  When provided the option of stairs or escalators, human nature is for people to take the escalator, even if they are capable of taking the stairs.  Escalators however have a high capital cost, a high level  of required maintenance, and high ongoing energy costs as they generally run continuously whether they are carrying people or not.

Some systems have addressed this issue from a variety of perspectives.  At the Copenhagen Metro, a deliberate choice was made to eliminate escalators from underground mezzanine levels to the surface in order to promote public health through the use of stairs.  On Sound Transit’s U-Link project, escalators were selectively deleted at some station entrances for cost reasons, where lower anticipated passenger volume did not warrant the high level of associated investment.  When eliminating escalators, it is advisable to increase the capacity of stairs in order to compensate for the reduced efficiency of moving large numbers of passengers quickly.

Photo Credit: VIA Architecture

Some transit designers have also found whimsical solutions to vertical circulation– as demonstrated by the ProRail Transfer Accelerator at the recently renovated Overvecht Rail Station in Utrecht, Holland and the musical stairs installed at Odenplan, Sweden. Both are playful means of encouraging passengers to exercise while taking transit.

Lighting Strategies:

Lighting strategies can be a significant contributor to reducing long-term energy consumption at transit stations.  Key principles include:

  • Use high efficiency fixtures with long lamp life
  • Use high light-reflectance materials to reduce the quantity of lighting required
  • Use controlled integration of daylight and electric light

Waterfront station, Canada Line, Vancouver: The Canada Line lighting design achieved energy savings by means such as avoiding over-lighting, integrating daylight sensors, and scheduling the lights to turn off during non-revenue hours.

Good integrated transit design includes an ongoing dialogue between structural design, urban design, and landscape teams to develop solutions that solve many issues simultaneously.  Some good examples of this type of “stacking” are as follows:Landscape and Structural Synergies:

Commercial Station, Millennium Line, Vancouver – this station platform was sited in the former Grandview railway cut, which is located several meters below street level.  During the public consultation process for the station design, local residents were concerned about the loss of habitat in the cut and about preserving the green space that it provided in the highly urban neighborhood.  VIA’s design solution was to line the east side of the cut using a stacking, precast ‘green wall ‘system that not only retained the soil but also provided space for planting and associated habitat.

Photo Credit: Ed White

Canada Line, Vancouver – one of the common issues associated with transit infrastructure is vandalism and anti-graffiti strategies.  On the Canada Line, the design team used a series of trellis structures around guideway columns to act as ‘green screens’.  These not only discouraged graffiti but also provided enhanced opportunities for landscape in the surrounding urban environment.  Green screens of this nature can also be used on bridge abutments, and the screens can be made hinged or demountable to allow for structural inspections as required.

Materials Strategies:
Many creative strategies are available to the design team that relate to the use of materials.  These fall into several general categories – Reuse and Salvage, Local materials, and Design for Durability.  Some examples are as follows:

Reuse and Salvage – Transit agencies that have been constructing systems for many decades often have a “boneyard” or similar source of materials that have been salvaged from previous projects, for use in current project design.  The re-envisioning and re-purposing of these materials can provide a creative design challenge to architects and urban designers, saving embodied energy and capital cost.

Photo Credit: Waterleaf Architecture

Where new transit projects require building demolition, it has become increasingly common to have salvage goals written into demolition contracts.  These materials can either be repurposed within the transit project, or accounted for as credit within the demolition contract.

Local Materials – The Millennium Line SkyTrain extension in Vancouver pioneered the use of wood in modern transit structures, a material not used for transit design for many decades.  On very old systems such as the London Underground and the Chicago “El”, it is still possible to see wood used in escalators and station platforms, but wood had generally been eliminated from transit design due to concerns about fire hazard, durability, and other technical considerations.

Three of the Millennium Line stations designed by VIA – Rupert, Renfrew, and Commercial – featured wood beams as prominently visible structural members.  This choice was made for a variety of reasons:  to honor the historical context of the timber industry in British Columbia, to promote the use of new wood technologies, and to add warmth and richness to the visual environment of the station platforms.  In order to address the technical concerns associated with wood, three ‘rules of engagement’ were established to govern the appropriate use of wood: 1) that it be located out of the ‘touch zone’, or minimum 3 meters above the platform surface, to prevent vandalism; 2) that it be completely weather protected; and 3) that it be dimensionally stable, in this case through the use of glu-lam technology.

Photo Credit: Ed White

Design for Durability – Often the most underrated form of sustainable design, the specification of materials that are durable is essential to successful transit design.  Not only does this save long-term cost associated with ongoing replacement or refinishing but it also avoids the indirect costs associated with station closures and down-time due to maintenance activities.  The use of stainless steel for transit handrails, as well as precast concrete or stone stair treads, and porcelain tiles for platform and concourse pavers, are essential strategies in durable transit station design.

In summary, good sustainable design directly supports good transit design.  A robust integrated design process will reveal the opportunities for efficiencies and synergies between disciplines, resulting in both short and long term cost savings and economies of effort during design and construction.