Wheel squeal
Wheel squeal is a high-pitched piercing noise that can occur as trains travel on curved track due to friction between the steel wheel and the top of the steel rail. Wheel squeal is usually louder than other types of train noise.
Wheel squeal is sometimes confused with flanging noise, which can also occur as trains travel on curved track, and brake squeal. Although they may sound similar, flanging noise and brake squeal have separate causes to wheel squeal and are therefore addressed differently.
RailCorp is a leader in research and development on wheel-rail noise, including wheel squeal, as demonstrated through ongoing industry research projects and technical studies. Through this research we have established that wheel squeal can occur as trains travel on curved track for two reasons:
- Very slight axle misalignments can cause loud wheel squeal and occur more often in freight trains than passenger trains.
- Friction conditions can cause moderate wheel squeal and vary, especially with the weather, but can be partially addressed using top-of-rail friction modifier devices.
Moreover our research indicates that wheel squeal is not caused by train speed, instead specific freight wagons tend to travel with very slight axle misalignments on curved track.
We recognise that wheel squeal can be a source of community concern and are carrying out a dedicated program which builds on our ongoing research and development and covers:
Axle alignment (angle-of-attack) monitoring system
We installed a monitoring system on curved track at Beecroft in late 2007 to measure axle alignment. We are continuing to analyse the data, with a focus on improving identification of the specific freight wagons that tend to travel with very slight axle misalignments on curved track.
Friction modifier devices
We have installed top-of-rail friction modifier devices in affected areas across our network since 1996. These devices minimise wheel squeal caused by friction conditions but do not eliminate all wheel squeal because they do not address axle misalignments. We are continuing to improve the technology used in these devices.
Noise barriers
Noise barriers are not the preferred option for reducing wheel squeal because they do not address either of the causes of the noise. Noise barriers may reduce noise if they block the line of sight between the noise source and receiver, however this means they are ineffective for elevated properties. In addition, noise barriers often obstruct existing views, create maintenance and emergency access issues and attract antisocial behaviour, such as graffiti.
Reports for freight operators and the environmental regulator
We regularly provide axle alignment feedback to the freight operators Pacific National and QR National so that they can consider addressing axle misalignment on their wagons. We also provide regular progress reports to the Office of Environment and Heritage to enable appropriate management by the environmental regulator.
More information
For information on industry research projects and technical studies, search for "wheel squeal" on the websites below: