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Solutions for a more sustainable railway

Adopting a rail transport system is, by definition, a first step towards sustainable development, helping us to meet our growing transport while generating less pollution than road traffic. However, it is now crucial that we find better solutions in terms of approaches, processes and materials in order to design more sustainable infrastructure. Although the railway can seem like a technical field that leaves little room for manoeuvre, several solutions now make it possible to meet this objective.

Adopting a rail transport system is, by definition, a first step towards sustainable development, helping us to meet our growing transport while generating less pollution than road traffic. However, it is now crucial that we find better solutions in terms of approaches, processes and materials in order to design more sustainable infrastructure. Although the railway can seem like a technical field that leaves little room for manoeuvre, several solutions now make it possible to meet this objective.

 

© Samuel Duplaix

The sustainable development issues related to the creation of a railway platform are:

  • Reducing and optimising infrastructure costs
  • Combating soil sealing (water permeability)
  • Using recycled materials in railway design
  • Reducing use of high carbon footprint materials such as concrete
  • Choosing more environmentally friendly manufacturing processes

The solutions presented below help to respond to some of these issues. Their implementation on several projects carried out by Egis ensures that their implementation is controlled.

 

Permeable tracks

Permeable tracks increase the volume of the substrate and thus its soil water capacity, limiting the need for watering and maintenance as well as the volume of concrete needed to build the platform. These tracks must be laid on stronger, load-bearing structures.
+ Higher substrate thickness
+ Lower amount of concrete
+ Reduced watering requirements and therefore operating costs
− Investment cost: ~4 to 25% more expensive

Rail covering using recycled tyres

This is an emerging solution that turns the rubber layer on tyres into a refined aggregate bound by a stable agent that can be used to wrapping rails.
+ Good compression resistance
+ Several suppliers available
+ Ability to dispense with rail joints

Electric welding

This solution concerns the use of electrical welding over thermite welding. There are two types of electrical welds: flash welding (rare) and arc welding. This is an emerging topic for which the industrial process in France is not yet fully complete, but which Egis is trying to develop.

+ No storage
+ Quicker to carry out
+ No harmful fumes
+ Less waste produced

Track on asphalt

+ Decrease in track bed thickness (~ 9cm)
+ Faster work
+ Reduced costs (savings of 5 to 15%)
+ Decrease in greenhouse gas emissions
+ No need for formwork
+ Can be used as a site track

− Need to increase the load-bearing capacity of earthworks
− Not possible to put asphalt along the entire distance (floating slabs near façades)

 

Routing of equipment by rail

Rails and sleepers represent a considerable amount of material to be transported to the site. To limit the impact of the many trucks needed to transport this equipment, it is wise to opt for rail transport whenever possible (where a freight and available storage space is nearby).

Non-concrete multi-tube trench

Replacing concrete multi-tube works with a multi-tube system using HDPE pipes and filling the trench with embankments
+ Financial savings of €100/ml
+ Less concrete
+ Reduced CO2 emissions (up to 70 kg eqC/ml)
− Difficult to implement in an urban environment

Single multi-tube system

Implementation of one multi-tube system instead of two
+ Less infrastructure works
+ Financial savings
+ Less concrete
− Risks of bundling strong and weak currents
− Safety issues

Key projects

  • Besançon Tramway: Inaugurated in August 2014, the design and construction of the city’s first tram line was carried out in accordance with a finely-tuned budget. With regard to the track itself,
    a green permeable platform was installed over 5.5 km of line. The sustainable development benefits include the limited volume of concrete used, no need for automatic watering systems and the planting of grass seedlings and species that consume little water and require little maintenance.
  • Line E of the Grenoble tramway, which commenced service in April 2014, covers a distance of 11.5 km. About 2,300 linear metres of track were built using non-concrete multi-tube
    systems in HDPE pipe. The choice of system has environmental and economic benefits with a total of €230,000 in savings made. The same choice was made for the full length of Grenoble’s line B extension (excluding crossing points).
  • Tram lines A and B in Dijon entered into service at the end of 2012. Spanning a total length of 19.7km, 90% of the tramway platform was built on asphalt (excluding floating
    slabs and certain intersections). Replacing the foundation concrete with asphalt concrete made it possible to reduce the depth of the earthworks, the as well as the cost and duration of the work, and provided greater flexibility during the construction phase.
  • The tram platform of Line B of the Strasbourg tramway, opened in 2000, was made of 800 linear metres of asphalt concrete. This ability to look back over 15 years without anomaly has confirmed the benefit and suitability of this solution.