SBB’s passenger trains are electric and therefore emit few pollutants. An exception to this are the diesel locos which SBB uses for shunting work, maintenance or freight deliveries. To protect the environment, SBB was prompt to equip its diesel fleet with particle filters, as this is the most efficient way to avoid diesel soot. To further reduce diesel use by its fleet, SBB has been purchasing dual-mode locomotives since 2012, which only use the auxiliary diesel motor on non-electrified route sections. In its climate strategy, SBB set itself the objective of turning its diesel fleet into a renewable-powered fleet by 2040.  

The abrasion of wheels, rails, breaks and contact wires generates particulates, mostly made of iron particles. Around 50% of these particulate emissions are generated by braking. Scientific investigations have shown that SBB emits around 1,000 to 1,400 tonnes of particulates annually. Though particulate emissions from rail operations are low, SBB is trying to reduce its emissions further. By consistently using electric rather than pneumatic braking, the amount of particulate matter emitted can be reduced further: electric braking means the motors serve as generators and feed energy back into the catenary. That saves energy and also means less particulate matter is emitted. Locomotive drivers learn how to do it with regular training.

Air quality in underground stations.

Underground stations act almost like closed-loop systems. Materials from rail operations are deposited in the environment. In stations, that means they cumulate on platforms, walls and in waste water from cleaning. Some of the materials stay in the air and repeatedly form dust or are carried further by trains. SBB started a project in 2014 at Zürich Museumstrasse station to look at how this cycle of material release and deposit works in a subterranean station. The study showed that particulate concentrations are falling thanks to increased usage of electric braking and do not pose an overall health risk to customers.