SBB's passenger trains are electric and so emit hardly any airborne pollutants. The diesel locomotives used by SBB for shunting, maintenance and local freight deliveries are an exception to this rule.

To protect the environment, SBB has progressively fitted its diesel fleet with particle filters – the most efficient means of containing diesel exhaust particulates. To reduce the diesel consumption of its fleet even further, SBB is increasingly deploying hybrid locomotives that only use their auxiliary diesel engines on non-electrified sections of track.

Fine dust largely consisting of iron particles is generated when wheels, rails, brakes and contact wires are subject to abrasion. Approximately 50 percent of these fine-dust emissions occur during braking. According to scientific studies, SBB generates around 1,000 – 1400 tonnes of fine dust each year.

Although rail operations account for only a small proportion of fine dust, SBB is trying to reduce its emissions even further. One way of doing this is to use electric brakes instead of mechanical brakes on passenger and freight trains. SBB has been regularly training its locomotive drivers on how in drive in an environmentally friendly and energy-saving manner since 2008.

Air quality in underground stations.

Underground stations act almost like closed-loop systems. Material emitted by rail operations gets deposited in the surrounding environment. In stations, this means it ends up on platforms and walls and in waste cleaning water. Some of this material just stays in the air and is constantly blown around or transported elsewhere by trains. In 2014, SBB will be investigating how this cycle of emissions and deposits functions in an underground station, with a project at Zurich's Museumstrasse station. The study shows that fine dust pollution is decreasing thanks to the increased use of electric brakes and that it does not present a risk to customers’ health in general.

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