Finally the Heavy Haul railways are unusual in demanding all of these things in some of the most hostile environments our planet has to offer. As deposits of minerals – especially iron ore – are exploited in ever more inaccessible places it becomes necessary to construct railways which can be built, operated and maintained in extreme climatic conditions. For components made from steel and concrete that is not too difficult, but there are two things in particular which function quite differently at extremes of temperature and humidity.
The biggest technical problems are those associated with plastics. Within the rail fastenings system plastics are used to provide electrical insulation, resilience and sometimes sacrificial wear elements. Materials such as nylon function well in most climates but are softened in hot, wet conditions and become brittle in dry conditions. A significant amount of work is being undertaken to find additives which can mitigate these effects or to evaluate the use of completely different engineering polymers which may not give the best performance in “average” conditions but which work acceptably well across a wide range of extreme environments.
The other thing which does not function so well in extreme climates is the human body! This may not sound like a technical issue but the fact is that we still expect to use a great deal of manual labour for track construction and maintenance. When Heavy Haul lines are built in inaccessible and inhospitable places the pressures to introduce more automation and to extend maintenance intervals are increased because of the additional human factors which must be taken into account.