GB2573095A

GB2573095A - Apparatus and method for delivering substances to and / or retaining substances on a railway traction contact surface

Info

Publication number: GB2573095A
Application number: GB1805102.9A
Authority: GB
Inventors: Hearn Graham; Cary Barnard Simon
Original assignee: COCATALYST Ltd
Current assignee: COCATALYST Ltd
Priority date: 2018-03-19
Filing date: 2018-03-28
Publication date: 2019-10-30
Anticipated expiration: 2038-03-28
Also published as: GB201805102D0; GB201804351D0; GB2573095B

Abstract

An apparatus 222 for mounting on a railway vehicle dispenses a friction modifying substance 230, such as water or sand, towards a railway traction contact surface, such as a rail 10 or a train wheel surface (fig.5,21), having an electrostatic source 250, such as a corona discharge or induction electrode, charging the substance promoting delivery to and/or retention of the substance to the surface. An additional electrode 251 may be used to charge the substance both before and after it contacts the rail surface. Preferably, the electrode may be 30 to 300mm from a nozzle 246, charging the substance at a position closer to the surface than the nozzle. Mounted on a railway vehicle the electrode may be between the dispenser 224 and a wheel 20, with further electrodes used between additional wheels.

Description

Apparatus and method for delivering substances to and / or retaining substances on a railway traction contact surface

The present invention is concerned with an apparatus and method for delivering substances to and / or retaining substances on a railway traction contact surface. More specifically, the present invention is concerned with an apparatus and method for delivering friction-modifying substances to and / or retaining friction-modifying substances on a railway rail or wheel surface to reduce sliding between a train wheel and the rail.

In the present application, the term "traction contact surface" is used to denote either a rail surface that contacts a train wheel in use, or a train wheel surface that contacts a rail surface in use.

The sliding or slippage between train wheels and rails is a well-known problem. Ideally, there should be sufficient friction between the wheel and rail to avoid any such sliding, especially under braking where safety is a concern. Further, excessive sliding can damage the train wheels (e.g. by creating "flat spots").

Reducing or eliminating sliding contact is also important when the train starts to move. Starting traction is important in the rail industry because it limits the maximum weight a locomotive can set in motion from a standing start.

Various factors contribute to potential sliding. One such factor is contaminants. Falling leaves settle on rails and may be compacted by passing trains, combining with other track-borne contaminants to form a low-friction coating on the rail, which subsequently reduces the friction between wheel and rail. During autumn, it is common in the UK (and other temperate countries) for this problem to lead to journey delays and in some cases even service cancellations. Significant costs are incurred by the rail industry to manage and mitigate this problem; common measures include vegetation removal, track sanding units on all trains, special trains to clean the tracks and creating autumn timetables with increased journey times.

Rails and wheels may also be contaminated by other matter, for example, water, rust, oil, solid particles etc. Water can, in certain circumstances, reduce friction between the wheel and rail (for example, rain, dew, snow, ice or general moisture due to humidity). Rust, solid particles (for example coal or dust), spilled fuel, oil, grease, hydraulic fluid and other chemicals can significantly impact friction. The problem with these contaminants is that they are localised and unpredictable. These conditions can be worsened in certain weather conditions, for example by temperature, humidity and atmospheric pressure.

Various methods and systems have been proposed for cleaning rails and increasing the adhesion between the railhead and a wheel. One solution is scraping, although this is difficult to control at high speed, and risks damage to the rail. Preventive methods (for example, leaf control) can be employed, but require a high degree of organisation and cost. Cleaning methods such as high-pressure water jetting are in use, but this requires the train to carry a large amount of water to supply jets of sufficient flow rate and pressure to clean the rail. Typically, separate special purpose trains are needed to carry the high volume water tanks for water jetting. These trains limit the ability of this solution to deal with changing effects during the day and risk interfering with normal service train operation. The use of friction improvers (for example, sand) has also been suggested, and in some countries such as the UK mandated. Sand can be used to improve traction from a standing start. Unfortunately, these substances are difficult to deliver in a manner which allows them to stay on the railhead surface. The best sanding systems only result in 25% of the sand lying on the railhead; often the real delivery performance is far worse due to poor set-up and maintenance of the sanding nozzles. Sand delivery rates can also drop in certain environmental conditions in e.g. strong crosswinds. The amount of sand delivered to the wheel rail interface has a major impact on the resulting wheel rail adhesion.

In the applicant's co-pending application GB1600470.7, it is proposed that a small amount of water (0.25 - 7.2 mls/metre of rail) is added. This, surprisingly, has the effect of increasing the coefficient of friction between the wheel and rail in the presence of contaminants. Unfortunately due to the relatively low water flow rate of this solution, the amount of water delivered to the rail may be affected by environmental effects such as crosswinds.

The present invention seeks to overcome, or at least mitigate, the problems identified in the prior art and to improve upon the applicant's earlier invention.

According to a first aspect of the invention there is provided an apparatus for attachment to a railway vehicle comprising: a friction-modifying substance dispenser configured to direct a friction-modifying substance towards a railway traction contact surface in use; and, an electrostatic source configured to electrostatically charge the dispensed friction-modifying substance to thereby promote delivery to and / or retention of the substance to the railway traction contact surface.

For the avoidance of doubt, by "railway traction contact surface" we include a rail or wheel surface, and also a rail or wheel surface which may be coated or partially coated with e.g. a leaf or other contaminant such as that present at the wheel rail interface. Advantageously, the present invention promotes better substance delivery and adhesion to the railway traction contact surface.

The friction-modifying substance is a liquid or a "fluidic solid"- i.e. a solid which behaves like a fluid (specifically it may comprise many small particles). Liquids include gels and greases. The friction modifying substance may comprise a liquid with a solid particles suspended therein. In the case of a liquid, the friction-modifying substance may be water. The present invention thereby improves upon the applicant's prior invention by promoting delivery of the water to the rail surface. In the event that the friction-modifying substance is a solid, granular material, the invention overcomes the problem with the prior art where e.g. sand may be blown off the rail or wheel surface, or simply bounce off when applied.

The use of an electrostatic source is beneficial for several reasons.

Firstly, droplets or particles can carry an electric charge which will attract them to, and deposit them on, the railway traction contact surface which is generally at earth potential. Once in contact with the railway traction contact surface, the application of an electrostatic charge will retain the substance on the rail at least temporarily (depending inter alia on the conductivity of the substance).

Secondly, electrostatic forces are very strong over distances of a few cm, which will at least partially counteract any aerodynamic forces produced by the motion of the train, or cross-winds.

Thirdly, commercially available electrostatic power modules are generally small and robust (usually potted in epoxy) and can be powered by a simple low-voltage DC input e.g. 12V. Varying the input voltage or switching the input on and off produces a proportional electrostatic voltage enabling simple control or modulation of the electrostatic effects.

Fourthly, although a high voltage is required (via a power converter), the power requirement is small because the droplet /particle charging currents are small (typically μΑ).

Preferably the friction-modifying substance is a friction-increasing substance.

Preferably, the electrode is a corona discharge electrode. Advantageously, corona discharge electrodes produce a stream of ionised particles which can, in turn, confer a charge to the frictionmodifying substance as they contact it.

Advantageously, corona discharge treatment is used to pre-condition surfaces to improve wetting in unrelated industries, such as coating, laminating and printing. The present invention has a similar wetting effect on the contaminants on the surface of the railway traction contact surface, making them more receptive to water application and thus reducing the time taken to reduce sliding.

Preferably the corona discharging is negative corona discharging.

Advantageously, negative corona discharge can create ozone which is known to be highly oxidising. Ozone is commonly used in sanitising applications in the food industry and for cleaning surfaces of organic matter. It is thought that ozone enhances the removal of contaminants in the present application.

In one embodiment, the electrostatic source is arranged to electrostatically charge the dispensed friction-modifying substance before the friction-modifying substance contacts the railway traction contact surface. Advantageously, this means that the substance is delivered to the surface more readily and reliably. In addition, the residual charge on the substance after contact at least temporarily retains the friction-modifying substance on the railway traction contact surface.

In a different embodiment, the electrostatic charge may be applied after contact between the frictionmodifying substance and the railway traction contact surface. Although less preferable, this embodiment would improve performance by reducing the amount of substance which rolls or flows off the railhead or wheel.

The electrostatic source may be provided at a distance of 30 to 300 mm from the nozzle.

Preferably the electrostatic source is configured to electrostatically charge the dispensed frictionmodifying substance at a position closer to the railway traction contact surface than the nozzle.

Charging too early will cause the droplets or particles to disperse (due to the similar charge). Therefore, in order to ensure as much substance is adhered to the rail or wheel surface as possible, it is advantageous to provide the charge as late as possible, but before the substance has contacted and bounced / flowed off the rail or wheel.

The electrostatic source may comprise an induction electrode as an alternative to a corona discharge electrode. The induction electrode would be at lkV- lOkV.

The invention provides a railway vehicle comprising an apparatus according to the first aspect.

If the system is configured to treat the rail (rather than the wheel), preferably the vehicle comprises a first rail-contacting wheel, in which the electrostatic source is positioned between the frictionmodifying substance dispenser and the first rail-contacting wheel.

The vehicle may comprise a second rail-contacting wheel in-line with the first rail-contacting wheel; and, a still further electrostatic source arranged to electrostatically charge the dispensed frictionmodifying substance on the rail between the first wheel and the second wheel.

Advantageously, this would facilitate the substance being retained on the rail for the second wheel without needing to dispense any new substance.

According to a second aspect of the invention there is provided a method for treating a railway traction contact surface with a friction-modifying substance comprising the steps of: dispensing a friction-modifying substance towards a railway traction contact surface; and, charging the friction-modifying substance to thereby promote adhesion to, and / or retention on, the railway traction contact surface.

Preferably there are provided the steps of: providing an electrostatic source; charging the friction-modifying substance with the electrostatic source.

Preferably the electrostatic source comprises a corona discharge electrode.

Preferably the step of charging comprises the step of: charging the friction-modifying substance before contact with the railway traction contact surface.

Preferably the method comprising the step of: charging the friction-modifying substance after contact with the railway traction contact surface.

Preferably the electrostatic source is a distance of 30 to 300 mm from the nozzle.

Preferably the method comprises the step of electrostatically charging the dispensed frictionmodifying substance at a position closer to the railway traction contact surface than the nozzle.

The electrostatic source may comprise an induction electrode as an alternative to a corona discharge electrode.

The present invention may be used with a liquid or a fluidic solid, such as sand. Sand is a good choice because it has a relatively low conductivity and as such will hold the electrostatic charge for longer when in contact with the railway traction contact (which is typically at earth potential).

An example apparatus and method in accordance with the present invention will now be described with reference to the accompanying Figures in which: FIGURE 1 is a side view of a railway vehicle comprising a first apparatus according to the present invention, which apparatus is configured to deliver a friction-modifying substance in liquid form; FIGURE 2 is a schematic view of the apparatus of Figure 1; FIGURE 3 is a schematic view of a second apparatus for use with the railway vehicle of Figure 1; FIGURE 4 is a schematic view of a third apparatus for use with the railway vehicle of Figure 1; and, FIGURE 5 is a schematic view of a fourth apparatus for use with the railway vehicle of Figure 1.

Referring to Figure 1, there is shown a set of rails 10 and a railway vehicle in the form of a train carriage 12. The rails 10 have an upper wheel-contacting surface 11. The carriage 12 comprises a body 14, and two bogies 16, 18 supporting the body. Each bogie comprises a set of wheels 20 which contact and roll along the track 10. Each wheel has a rail-contacting surface 21. The surfaces 11, 21 are railway traction contact surfaces. The train moves in direction D (although it will be noted that most trains are configured to move in both directions).

The first embodiment

Figure 2 shows an apparatus 22 according to the present invention mounted on the train carriage 12. The apparatus comprises a dispenser assembly 24 and an electrostatic source assembly 26.

The dispenser assembly comprises a container 28 which contains a friction-modifying fluid 30. The container 28 has an outlet 32 to a pump 34, which in turn has an outlet 36 to a nozzle 38. If used with a liquid, the nozzle 38 is selected to atomise the liquid into a stream of droplets. The nozzle 38 is mounted to the apparatus 22 (and hence the carriage 12) so as to be directed towards the upper surface 11 of the rail 10. In use, the nozzle 38 is directed towards the wheel-rail contact region of the railhead.

The electrostatic source assembly 26 comprises a power source 40 and a high voltage (in the order of lOkV - 60kV) corona electrode 42 configured to produce an electrostatic discharge 46 directed towards the rail surface 11 in use. It is positioned behind the nozzle 38 relative to the direction of travel D, i.e. between the nozzle 38 and leading wheel 20. A controller 44 is provided to selectively activate the pump 34 and electrostatic source assembly 26. The controller receives a signal from the vehicle operator or brake system controller to activate or deactivate it.

In use, as the train travels in direction D, the friction-modifying fluid 30 is pumped to the nozzle 38 and ejected to a non-ionised stream 30' of friction-modifying substance towards the rail surface 11. It will be noted that due to the angle of the nozzle 38 and the motion in direction D of the carriage, the stream 30' moves rearwardly relative to the carriage 12. As the electrode 42 passes over the non-ionised stream 30' it ionises the friction-modifying substance to create an ionised stream 30". The charged particles of the ionised stream 30" are drawn to and contact the rail surface 11. This is a result of the charge on the ionised stream 30" inducing an opposite charge on the rail, resulting in an attraction between the two.

The first embodiment is a low-cost liquid-dispensing system.

The second embodiment

Figure 3 shows an apparatus 122 according to the present invention mounted on the train carriage 12. The apparatus comprises a dispenser assembly 124 and an electrostatic source assembly 126.

The dispenser assembly comprises a container 128 which contains a friction-modifying substance 130. The container 128 has an outlet 132 to a pump 134, which in turn has an outlet 136 to a pressure accumulator 138. The pressure accumulator 138 has an outlet 140 to a proportional flow control valve 142 which has an outlet 144, leading to a nozzle 146. The nozzle 146 is mounted to the apparatus 122 (and hence the carriage 12) so as to be directed towards an upper surface 11 of the rail 10. In use, the nozzle 146 is directed towards the wheel-rail contact region of the railhead.

The electrostatic source assembly 126 comprises a power source 148 and a high voltage (lOkV to 60kV) corona electrode 150. The electrode 150 is positioned to be directed at the substance downstream of the nozzle 146. It is configured to produce an electrostatic discharge 152 directed towards the rail surface. A controller 154 is provided to selectively activate the pump 134, the proportional flow control valve 142 (e.g. through pulse width modulation) and electrostatic source assembly 126. The controller receives a signal from the vehicle operator to activate or deactivate it.

In use, as the train travels in direction D, the friction-modifying fluid 130 is pumped to the pressure accumulator 138 until a pre-set pressure value is reached. When activated, the controller 154 operates the proportional flow control valve 142, releasing the friction-modifying fluid to flow to the nozzle 146. A non-ionised stream 130' of friction-modifying substance is ejected towards the rail surface 11. It will be noted that due to the motion in direction D of the carriage, the stream 130' moves rearwardly relative to the carriage 12. As the stream 130' passes under the electrode 150 it is ionised to create an ionised stream 130". The charged particles of the ionised stream 130" are drawn to and contact the rail surface. This is a result of the charge on the ionised stream 130" inducing an opposite charge on the rail, resulting in an attraction between the two.

The second embodiment is a liquid dispenser design with more robust flowrate control, especially in situations where higher flowrates are required.

The third embodiment

Figure 4 shows an apparatus 222 according to the present invention mounted on the train carriage 12. The apparatus comprises a dispenser assembly 224 and an electrostatic source assembly 226.

The dispenser assembly comprises a container 228 which contains a solid particulate frictionmodifying substance 230. The container 228 has an outlet 232 to a metering valve 234, which in turn has an outlet 236 to a venturi unit 238. An air supply 240 is connected to the venturi unit 238 by an air-line 242. The venturi unit 238 has an outlet 244 to the nozzle 246. The nozzle 246 is mounted to the apparatus 222 (and hence the carriage 12) so as to be directed towards an upper surface 11 of the rail 10. In use, the nozzle 246 is directed towards the wheel rail contact.

The electrostatic source assembly 226 comprises a power source 248 and a high voltage (lOkV to 60kV) corona electrode 250. The electrode 250 is positioned downstream of the nozzle 246 and is configured to produce an electrostatic field 252 directed towards the rail surface. An additional electrode 251, producing an electrostatic field 253 is positioned between the first electrode 250 and the wheel 20. A controller 254 is provided to selectively activate the metering valve 234, the air supply 240 and electrostatic source assembly 226. The controller receives a signal from the vehicle operator to activate or deactivate it.

When activated, the controller 254 operates the metering valve 234, releasing the solid particulate friction-modifying substance 230 to flow to the venturi unit 238. The solid particulate frictionmodifying substance 230 is mobilised in the venturi unit by air delivered from the air supply 240 causing it to travel towards the nozzle 246. A non-ionised stream 230' of solid particulate frictionmodifying substance is ejected through the nozzle 246 towards the rail surface 11. As the stream 230' passes under the electrode 250 it is ionised to create an ionised stream 230". The charged particles of the ionised stream 230" are drawn to and contact the rail surface 11 and adhere thereto forming a layer 230'" of friction-modifying substance. The second electrode 251 acts to replenish the charge held by the particulate solid friction-modifying substance 230'" on the rail surface increasing the adhesion of the substance to the rail surface 11. As such, the first electrode primarily promotes delivery to the rail, and the second primarily promotes retention on the rail.

The third embodiment makes use of a solid particulate dispenser commonly used in the railway industry.

The fourth embodiment

Figure 5 shows an apparatus 322 according to the present invention mounted on the train carriage 12. The apparatus comprises a dispenser assembly 324 and an electrostatic source assembly 326.

The dispenser assembly 324 comprises a container 328 which contains a friction-modifying substance 330. The container 328 has an outlet 332 to a pump 334, which in turn has an outlet 336 to a nozzle 338. If used with a liquid, the nozzle 338 is selected to atomise the liquid into a stream of droplets. The nozzle 338 is mounted to the apparatus 322 (and hence the carriage 12) so as to be directed towards an upwardly facing region of the surface 21 of the wheel 20. The surface 21 comprises part of the radially outwardly facing surface of the wheel 20 which contacts the rail 10 in use.

The electrostatic source assembly 326 comprises a power source 340 and a plurality of high voltage (in the order of lOkV - 60kV) corona electrodes 342, 347 and 349 configured to produce electrostatic discharges 346, 348 and 350 directed towards the wheel surface 21 in use. The electrodes are positioned behind the nozzle 38 relative to the direction of wheel rotation R, i.e. between the nozzle 338 and the point of wheel-rail contact 23. A controller 344 is provided to selectively activate the pump 334 and electrostatic source assembly 26. The controller receives a signal from the vehicle operator or brake system controller to activate or deactivate it.

In use, as the train moves in direction D, and the wheel rotates in direction R, the friction-modifying substance 330 is pumped to the nozzle 338 and ejected to a non-ionised stream 330' of frictionmodifying substance towards the wheel surface 21. It will be noted that due to the angle of the nozzle 338, the stream 330' moves towards the electrostatic field 346 generated by the first electrode 342. As the non-ionised stream passes the electrostatic field 346 it is converted into an ionised stream 30". The charged particles of the ionised stream 30" are drawn to, and contact, the wheel surface 21. This is a result of the charge on the ionised stream 30" inducing an opposite charge on the wheel, resulting in an attraction between the two and a coating of ionised friction-modifying substance 330"'on the wheel surface 21.

The second and third electrodes 347 and 349 act to replenish the charge held by friction-modifying substance 330'" on the rail surface. For semi-conductive and conductive friction modifying substances this is particularly useful as the charge would otherwise dissipate quite quickly, potentially causing the material to leave the surface 21. As such, the first electrode 342 primarily promotes delivery to the rail, and the second and third electrodes 347, 349 primarily promote retention on the wheel.

The fourth embodiment is a liquid-dispensing system configured to deliver friction modifier to the train wheels.

Variations fall within the scope of the present invention.

It will be understood that the friction-modifying substance 30, 130 may be: • A liquid, such as; o Water; o gels; o Oils; and, o Greases. • A fluidic solid, specifically a particulate solid such as: o Sand; o Other ceramic particles; o Rubber / elastomeric / polymeric particles. • A combination of solid and fluid such as: o A solid / particulate phase suspended in a fluid, e.g. a gel containing metal particles to improve conductivity

In the event that the substance is a liquid, and in particular water, the flow rate is selected to provide in the range of 0.25 to 7.2 ml/m of rail section for a single apparatus. Evidently this is linked to train carriage speed, and it is understood that the controllers 44, 144 are configured to receive the train speed and calculate the flow rate provided by the pumps 38,138 to provide this amount of liquid per metre of rail.

The apparatus according to the invention may be positioned at either end of a railway vehicle to provide coverage in alternate directions of travel.

The apparatus according to the invention may be positioned at multiple locations along the length of a train.

The apparatus may be provided as a self-contained unit (e.g. for retrofit) or may comprise separate sub-systems. For example, the electrode and controller may be retrofitted to a train with an existing sanding system.

An individual apparatus may be provided per wheel, per wheel set or per bogie.

The substance may derive a charge from other means, for example by friction or tribo-charging.

The system of Figure 5 (the wheel-treating system) may be used in combination with any of the systems of Figures 2 to 4 to treat both the wheel and rail.

Claims

1. An apparatus for mounting on a railway vehicle comprising: a friction-modifying substance dispenser configured to direct a friction-modifying substance towards a railway traction contact surface in use; and, an electrostatic source configured to electrostatically charge the dispensed friction-modifying substance to thereby promote delivery to and / or retention of the substance to the railway traction contact surface.

2. An apparatus according to any claim 1, in which the electrostatic source comprises a corona discharge electrode.

3. An apparatus according to claim 1 or 2, in which the electrostatic source is arranged to electrostatically charge the dispensed friction-modifying substance before the friction-modifying substance contacts the railway traction contact surface.

4. An apparatus according to claim 3, comprising a further electrostatic source arranged to electrostatically charge the dispensed friction-modifying substance after the friction-modifying substance contacts the railway traction contact surface

5. An apparatus according to claim 1 or 2, in which the electrostatic source is arranged to electrostatically charge the dispensed friction-modifying substance after the friction-modifying substance contacts the railway traction contact surface.

6. An apparatus according to any preceding claim, in which the electrostatic source is a distance of 30 to 300 mm from the nozzle.

7. An apparatus according to any preceding claim, in which the electrostatic source is configured to electrostatically charge the dispensed friction-modifying substance at a position closer to the railway traction contact surface than the nozzle.

8. An apparatus according to claim 1, in which the electrostatic source comprises an induction electrode.

9. An apparatus according to any preceding claim, in which the railway traction contact surface is a rail surface.

10. An apparatus according to any preceding claim, in which the railway traction contact surface is a train wheel surface.

11. A railway vehicle comprising an apparatus according to any of claims 1 to 10.

12. A railway vehicle according to claim 11, dependent on claim 9, comprising a first railcontacting wheel, in which the electrostatic source is positioned between the friction-modifying substance dispenser and the first rail-contacting wheel.

13. A railway vehicle according to claim 12, comprising: a second rail-contacting wheel in-line with the first rail-contacting wheel; and, a still further electrostatic source arranged to electrostatically charge the dispensed frictionmodifying substance on the rail between the first wheel and the second wheel.

14. A method for treating a rail surface with a friction-modifying substance comprising the steps of: dispensing a friction-modifying substance towards a railway traction contact surface; and, charging the friction-modifying substance to thereby promote adhesion to, and / or retention on, the railway traction contact surface.

15. A method according to claim 13, comprising the step of: providing an electrostatic source; charging the friction-modifying substance with the electrostatic source.

16. A method according to claim 15, in which the electrostatic source comprises a corona discharge electrode.

17. A method according to any of claims 14 to 16, in which the step of charging comprises the step of: charging the friction-modifying substance before contact with the railway traction contact surface.

18. A method according to any of claims 14 to 17, comprising the step of: charging the friction-modifying substance after contact with the railway traction contact surface.

19. A method according to any of claims 14 to 18, in which the electrostatic source is a distance of 30 to 300 mm from the nozzle.

20. A method according to any of claims 14 to 19, comprising the step of electrostatically charging the dispensed friction-modifying substance at a position closer to the railway traction contact surface than the nozzle.

21. A method according to claim 14, in which the electrostatic source comprises an induction electrode.

22. A method according to any of claims 14 to 21, in which the railway traction contact surface is a rail surface.

23. An apparatus according to any of claims 14 to 21, in which the railway traction contact surface is a train wheel surface.

24. A method of modifying a railway vehicle comprising the steps of: providing a railway vehicle having friction-modifying substance dispenser configured to direct a friction-modifying substance towards a railway traction contact surface in use; and, providing an electrostatic source; mounting the electrostatic source to the railway vehicle such that it is configured to electrostatically charge the dispensed friction-modifying substance to thereby promote delivery to and / or retention of the substance to the railway traction contact surface in use.

25. An apparatus according to any of claims 1 to 10, a vehicle according to any of claims 11 to 13 or a method according to any of claims 14 to 24 in which the dispensed friction-modifying substance is a liquid.

26. An apparatus according to any of claims 1 to 10, a vehicle according to any of claims 11 to 13 or a method according to any of claims 14 to 24 in which the dispensed friction-modifying substance is water.

27. An apparatus according to any of claims 1 to 10, a vehicle according to any of claims 11 to 13 or a method according to any of claims 14 to 24 in which the dispensed friction-modifying substance is a fluidic solid.

28. An apparatus according to any of claims 1 to 10, a vehicle according to any of claims 9 to 13 or a method according to any of claims 14 to 24 in which the dispensed friction-modifying substance is sand.