Live Coverage: L.B. Foster's 'The Role of Trackside Friction Management Systems in Improving Public Health' Webinar

RAILTARGET is bringing you live updates from the L.B. Foster webinar on the role of trackside friction management in public health, exploring how managing the wheel-rail interface can reduce noise, vibration and wear, while cutting maintenance needs and improving conditions for passengers, railway workers and communities living alongside rail lines.

12:00 Jackie Butterfield, Principal Applications Engineer at L.B. Foster Europe, opens the webinar by looking at railway noise from a public health perspective. Excessive noise, she explains, can increase stress and anxiety, while persistent noise at night can disturb sleep and, over time, contribute to wider health problems.

Sleep disturbance has been linked to high blood pressure, cardiovascular disease, heart attacks and strokes, as well as cognitive impairment. Long-term exposure to high noise levels can also damage hearing. And the problem does not stop with people living next to railway lines as passengers and railway employees are exposed as well.

Butterfield points to figures showing the scale of the issue. According to data cited from the UK Health Security Agency, around 13,000 years of healthy life were lost in 2018 because of railway noise alone. The European Environment Agency estimates that around 19 million people across the EU are exposed to railway noise levels above 55 dB.

She also referred to World Health Organization recommendations intended to limit the health impact of environmental noise. The wider point, she said, is that unnecessary railway noise has measurable consequences and should be treated as more than simply an inconvenience for people living close to the tracks.

A 2022 report by the International Union of Railways (UIC) looked specifically at railway noise and its effects on human health. It reviewed existing evidence on health and nuisance effects and surveyed 18 UIC members, including Network Rail in the UK, about the noise complaints they receive and how they respond to them. The report also says the costs associated with railway noise are estimated at around EUR 4 billion.

12:10 Butterfield cited research published by the UK Railway Industry Association in 2024, which estimated that passenger traffic in Britain could increase by 37% to 97% over the next 30 years. Urban rail is expanding as well: more metro, light rail and tram systems mean more people are likely to live, work or travel close to railway operations. Freight trains also tend to operate heavily during the night, meaning railway activity increasingly reaches into periods when noise is particularly disruptive.

Before moving into the technical side of friction management, Butterfield clarified three terms that are often used interchangeably: sound, noise and vibration. Sound is created by audible fluctuations in air pressure. Noise is unwanted sound, with railway noise normally expressed in decibels and often in dBA, which adjusts the measurement to reflect the sensitivity of human hearing.

Vibration is different. It involves particles in solid materials oscillating relative to one another. Those vibrations can then be reduced, amplified or radiated through surrounding structures until they eventually become audible sound.

12:15 Butterfield then breaks railway noise down into three main sources. The first is aerodynamic noise, caused by the movement of a train through the air and the turbulence it creates. The second is traction noise, generated by the train’s propulsion system and auxiliary equipment. The third is mechanical, or rolling, noise, created by the interaction between the vehicle and the track.

Rolling noise is produced when irregularities on the surfaces of the wheel and rail generate vibrations at the contact point. These vibrations travel through the wheels, rails and track structure and can then radiate into the surrounding environment as noise.

Exactly how much noise is produced depends on several factors: the condition and geometry of the wheel and rail, the design of the vehicle and track, environmental conditions and the layers present at the wheel–rail interface. Speed also plays a major role. Butterfield notes a direct relationship between train speed and noise generation: doubling the speed can increase railway noise by roughly 9 dB. Sound levels fall as the distance from the source increases, while nearby structures can either absorb or reflect noise and change what residents, passengers or railway workers ultimately hear.

12:20 Butterfield says human hearing covers roughly 20 Hz to 20 kHz, but our ears are most sensitive between about 1 kHz and 10 kHz, which is important because railway noise is often irregular. A constant background sound may be relatively easy to ignore, while a sudden squeal can trigger what Butterfield described as an "arousal event." The brain reacts to the unexpected change, adrenaline rises and a stress response can follow. At night, that can interrupt deep sleep and make it harder to fall asleep again.

Different railway noises also sit in different frequency ranges. Rolling noise spans roughly 30–2,500 Hz, while rumble linked to corrugation is usually between 200 Hz and 1 kHz. Flat spots and ground-borne vibration tend to sit lower. Two of the most familiar railway noises, however, fall right into the range where human hearing is especially sensitive. Top-of-rail squeal typically occurs between 1 and 5 kHz, while flanging noise can reach 5 to 10 kHz.

12:25 Flanging noise is usually heard as buzzing, grinding or hissing and typically falls within the 5–10 kHz range. It is generated when the wheel flange contacts the gauge face or gauge corner of the rail. Its intensity depends on the lateral forces at that contact and on friction both at the top of the rail and between the flange and gauge face. In the example shown during the webinar, the strongest peaks appeared around 6.3 and 10 kHz.

The second type is top-of-rail, or curve, squeal, the familiar high-pitched whistle often heard on tighter curves, usually below around 350 metres in radius, although it can also appear on larger curves. Curve squeal is generally linked to oscillation at the wheel–rail contact. As a vehicle enters a curve, the different paths taken by the inner and outer wheels create lateral forces and increasing creepage, or microscopic relative movement at the contact.

Under some conditions, this can develop into a repeated stick-slip cycle. Butterfield compared it to running a finger around the rim of a wine glass: once the system starts oscillating at a resonant frequency, the characteristic whistle appears.

To explain that process, Butterfield showed the third body layer between a dry wheel and rail. This layer contains hard, brittle wear particles, typically iron oxide, along with brake dust and other debris. Under normal rolling conditions, the particles remain relatively loosely distributed. As creepage forces increase in a curve, they are pushed closer together. They first deform, then start to fracture, and finally the spaces between them collapse.

Butterfield linked this final stage to the negative friction behaviour that can contribute to stick-slip oscillation. As the train keeps moving, fresh material enters the contact area and the cycle starts again: rolling, elasticity, breaking and void collapse.

The third problem was rail corrugation, which creates the distinctive roaring sound sometimes heard when trains pass over damaged rail. Its frequency depends on both train speed and the wavelength of the corrugation, so the sound changes with operating conditions.

Some forms of corrugation are also linked to oscillation at the wheel–rail interface and therefore partly to friction. That is the common thread between flanging, curve squeal and corrugation: changing friction conditions can change both the level and character of the noise.

12:30 Butterfield says that friction management is not the only way to reduce railway noise. One option is to control wheel and rail roughness. Rail grinding can reduce noise by up to around 5 dBA, while wheel turning and friction management can also help by limiting surface damage.

Another approach is to reduce vibration using rail damping, wheel damping or optimised wheel and rail profiles. Sound can also be tackled after it is generated. Noise barriers, sound-damping windows and building insulation can provide reductions of more than 10 dBA in some cases. Noise can also be reduced through track and vehicle design, for example by increasing curve radii or improving vehicle steering to limit unwanted wheel–rail contact.

12:35 Friction management is essentially the controlled introduction of material into the wheel–rail interface to influence how friction behaves to keep friction within the right range for a particular part of the wheel and rail. For flanging noise, products can be applied at the gauge face or gauge corner of the rail using trackside equipment. They can also be delivered directly from the vehicle through solid sticks or onboard spray systems using grease or oil.

Friction modifiers are designed to keep friction at an intermediate level: high enough to maintain safe traction and braking, but low and stable enough to limit the mechanisms behind wear, squeal and corrugation. Butterfield said L.B. Foster’s friction modifiers typically target a coefficient of around 0.3 to 0.4.

Butterfield also explained how the products are applied. Older gauge-face systems were often mechanical or hydraulic, but modern electrical units offer much more precise control. An integrated control box and wheel sensors can determine when the system activates, after how many axles and how much product is dispensed. Remote monitoring can also track product levels and operating parameters, allowing faults to be checked without unnecessary visits to the track.

Systems are available with different tank sizes and power options, including solar and mains power, and can be configured for either grease or top-of-rail friction modifier. The applicator itself depends on where the product needs to go. Gauge-face and check-rail bars use several ports to spread grease across the contact area, while top-of-rail bars place the friction modifier directly onto the rail head. Passing wheels then pick up the material and carry it farther along the track. How far it travels, known as the carry-down distance, depends on both the equipment and the characteristics of the product.

12:40 For flanging, grease is applied to the gauge face or gauge corner and reduces friction to below around 0.1. It also acts as a barrier between the surfaces, reducing vibration, wear and the roughness that can generate further noise.

Top-of-rail products work differently. Butterfield says that several types of friction modifier are available, including oil-, grease-, water- and hybrid-based products, but not all behave the same way against curve squeal.

She focused on L.B. Foster’s KELTRACK, a water-based friction modifier containing solid particles. Once applied, the water evaporates and leaves a thin film on the rail. Butterfield said extensive braking trials have shown that the product does not compromise traction or braking performance.

Its main role in noise reduction is to change the behaviour of the third body layer discussed earlier. The solid particles help cushion the harder, brittle material between wheel and rail, limiting the breaking and void-collapse stages that can drive stick-slip oscillations.

Instead of friction falling after reaching a peak, the modifier produces a more stable, positive friction characteristic. That can prevent the oscillation from developing in the first place and reduce curve squeal and some corrugation mechanisms.

12:45 Butterfield says that friction management is not simply a noise-control measure. The same wheel–rail conditions that create squeal and corrugation can also contribute to wear, rolling contact fatigue, high lateral forces and greater energy consumption. Based on trials and customer data presented during the webinar, short-term benefits can include 25–60% reductions in wheel and rail wear, lower noise levels, reduced risk of high lateral-force derailments and fuel or energy savings of up to around 5%.

Over the longer term, operators can also see less need for rail grinding, fewer wheel and rail defects, reduced track damage and better ride quality as vehicles steer more effectively.

Butterfield said cost-benefit studies have shown that the payback period for friction management can be less than one year, although the actual savings vary from site to site. For L.B. Foster, these benefits mean friction management should not be seen only as a response to a problem after it appears.

Butterfield described a proactive friction management strategy as a "sustainability enabler" rather than simply a maintenance expense. It can contribute to all three main areas of sustainability: social, environmental and economic. The social benefit is the most obvious: less intrusive railway noise can improve conditions for residents, passengers and rail employees.

Environmentally, lower friction-related losses can reduce energy consumption, while longer wheel and rail life means fewer components need to be manufactured and replaced, important because steel rail and wheels carry a substantial carbon footprint.

There is also a direct economic benefit through longer asset life and fewer corrective maintenance interventions. Butterfield cited calculations from customers in the United States suggesting that every dollar spent on friction management can generate around four dollars in maintenance savings. She says well-designed friction management strategy can improve not only the performance of railway infrastructure, but also the quality of life of the people who live near, travel on or work on the railway.

12:50 During Q&A session, Butterfield explained that performance depends largely on the formulation of the grease. At high temperatures, some greases can soften once they approach their dropping point. This reduces their "column strength," aka the ability of the grease to stand proud of the applicator bar so that passing wheels can pick it up effectively.

Cold weather can create the opposite problem. If the grease becomes too stiff, it may be difficult to pump through the system. This is why different formulations are available for summer and winter conditions, with different viscosities and NLGI grades.

Water-based friction modifiers tend to perform more consistently across temperature changes, although very heavy rain can wash the product from the rail more quickly. Butterfield said that the formulations are designed to adhere to the rail and resist normal water wash-off, but torrential rain will naturally reduce their persistence. She also said that changing climate conditions, including increasingly high summer temperatures in the UK, make it particularly important to select products suited to the full temperature range expected on the railway.

This concludes the 'The Role of Trackside Friction Management Systems in Improving Public Health'. Thank you for tuning in with RAILTARGET for the updates.