Abstract:
A system and method for friction management for managing and controlling an application of a friction modifying agent to an area of contact between a railway wheel and a railway rail over which the wheel is traversing to selectively modify the coefficient of friction at the contact area. The system comprises a sensor for detecting a parameter relating to the operation of the railway train. A controller is responsive to the sensor and controls the application of a friction modifying agent to the rail as a function of the parameter. An applicator is responsive to the controller and applies the friction modifying agent to the area of contact between the railway wheel and rail. The invention also includes a method for railway train friction management for managing and controlling the application of friction modifying agent to an area of contact between railway wheel and railway rail over which the wheel is traversing to selectively modify the coefficient of friction at the contact area. The method comprises sensing a parameter related to the operation of the railway train and applying the friction modifying agent to the area of contact between the railway wheel and rail as a function of the sensed parameter.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 60/419,673, filed on Oct. 18, 2002, the entire disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to railroad friction enhancing and friction reducing systems. More particularly, the invention relates to systems and methods for automatically controlling the application of the cohesion or friction modifiers to a railway system. 
     2. Background 
     Locomotives and transit vehicles as well as other large traction vehicles are commonly powered by electric traction motors coupled in driving relationship to one or more axles of the vehicle. Locomotives and transit vehicles generally have at least four axle-wheel sets per vehicle with each axle-wheel set being connected via suitable gearing to the shaft of a separate electric motor commonly referred to as a traction motor. In the motoring mode of operation, the traction motors are supplied with electric current from a controllable source of electric power (i.e., an engine-driven traction alternator) and apply torque to the vehicle wheels which exert tangential force or tractive effort on the surface on which the vehicle is traveling (i.e., the parallel steel rails of a railroad track), thereby propelling the vehicle in a desired direction along the right of way. 
     Locomotives used for heavy haul applications typically must produce high tractive efforts. Good adhesion between each wheel and the surface is required for efficient operation of the locomotive. The ability to produce these high tractive efforts depends on the available adhesion between the wheel and rail. Many rail conditions such as being wet or covered with snow or ice require an application of friction enhancing agent such as sand to improve the adhesion of the wheel to the rail. Therefore, locomotives typically have sand boxes on either end of the locomotives, and nozzles to dispense the sand (both manually and automatically) to the rail on either side of the truck. 
     Maximum tractive or braking effort is obtained if each powered wheel of the vehicle is rotating at such an angular velocity that its actual peripheral speed is slightly higher (motoring) than the true vehicle speed, i.e., the linear speed at which the vehicle is traveling, usually referred to as “ground speed” or “track speed”. The difference between tractive wheel speed and track speed is referred to as “creepage” or “creep speed.” There is a variable value of creepage at which peak tractive effort is realized. This value, commonly known as the optimal creep setpoint is a variable that depends on track speed and rail conditions. So long as the allowable creepage is not exceeded, this controlled wheel slip is normal and the vehicle will operate in a stable microslip or creeping mode. If wheel-to-rail adhesion tends to be reduced or lost, some or all of the tractive wheels may slip excessively, i.e., the actual creep speed may be greater than the maximum creep speed. Such a gross wheel slip condition, which is characterized in the motoring mode by one or more spinning axle-wheel sets, can cause accelerated wheel wear, rail damage, high mechanical stresses in the drive components of the propulsion system, and an undesirable decrease of tractive effort. 
     The peak tractive effort (TE) limits the pulling/braking capability of the locomotive. This peak tractive effort is a function of various parameters, such as weight of the locomotive per axle, wheel rail material and geometry, and contaminants like snow, water, grease, insects and rust. Contaminants in the wheel/rail interface reduce the maximum adhesion available, even at the optimal creep setpoint. 
     While the locomotives most often require friction enhancing agents, locomotives also require, in some situations, the application of a lubricant to reduce the wear of the locomotive wheel flanges. For example, when a locomotive is traversing a section of track with a curve. For a locomotive or a consist of locomotives that are always oriented in the same way, maximum benefit for wheel-rail wear of both the cars and the locomotives is provided by lubricating the gage side of the rail or wheel flanges on the high rail in the front and simultaneously lubricating the top of the two rails in the trailing end of the locomotive or the locomotive consist. Control of the rail gage side (RAGS) lubricator as well as the top of rail (TOR) lubricator can be done by the same controller for one locomotive or two controllers located in different locomotives for the case of a locomotive consist. 
     While locomotive often require increased cohesion, generally non-locomotive railway cars trailing the locomotives operate most efficiently at lower cohesion or friction levels. As such ,friction and therefore pull weight of railway cars. Lubricant applied to the top of the rail and possibly to the gage side of the rail behind the last axle of the last locomotive results in reduced friction and wear of the trailing car wheels. In other systems, such as a flange lubrication system, grease is applied to the flanges of the locomotive wheels in order to reduce friction between the flange and the wheel thereby reducing fuel usage and increase rail and wheel life. The system dispenses a controlled amount of lubrication, based on locomotive speed and direction, to the inside flange of wheel to lubricate the wheel/flange interface on the trailing axles of the locomotive/train. Presently, nozzle placement is based on customer choice, and the nozzles can be applied to multiple axles and always in pairs (left and right side). The lubrication is typically of a graphite base. 
     It is desirable to reduce the coefficient of friction for the trailing cars as the reductions in the coefficient of friction directly reduces the pull weight and directly improves the fuel efficiency of the locomotive consist. Managing the coefficient of friction of the cars can result in a 10 to 30 percent increase in fuel efficiency. 
       FIG. 1  illustrates a typical prior art locomotive  122  having a friction modifying agent to increase the coefficient of friction. In this case the friction modifying agent is sand and the sanding system applies sand to the rails. Sand is stored in a short hood sand box  118  or a long hood sand box  120 . The illustrated example includes eight sand nozzles  102 - 116 . In the illustrated example, the locomotive  122  has two trucks  124  and  126 ; the front truck  124  has one nozzle in the front left  102 , one nozzle in the front right  104 , one nozzle in the rear left  106 , and one nozzle in the rear right  108 . The rear truck similarly has one nozzle in the front left  110 , one nozzle in the front right  112 , one nozzle in the rear left  114 , and one nozzle in the rear right  116 . Chart  128  of  FIG. 1  illustrates when each of the nozzles are active. For example, sand nozzle  114  is active in the reverse direction if lead axle sand or auto sand or trainline sand is enabled. 
       FIG. 2  illustrates a prior art schematic diagram of the sanding system  200  of FIG.  1 . The system  200  includes a compressed air reservoir  202 , one sand box for each truck  204  for the front and  206  for the rear, one manual air valve for each truck ( 208  for the front truck and  210  for the rear truck), two electrically controlled sand valves for each truck ( 212  and  214  for the front truck and  216  and  218  for the rear truck), and two nozzles for each of these electrically controlled sand valves ( 102  and  104  for the forward front truck valves,  106  and  108  for the reverse front truck valves,  110  and  112  for the forward rear truck valves,  114  and  116  for the reverse rear truck valves). A locomotive control system  220  enables the appropriate sand valves based on the inputs from the operator or train lines, or when an adhesion control system determines that the rail conditions are poor and sanding will yield a higher tractive effort. Lubricants may be applied to the top of the rail or to the rail gage side in a similar manner (not illustrated). 
       FIG. 3  illustrates an exemplary adhesion creep curve  300  for a locomotive traversing a rail. As illustrated, curve  302  depicts the adhesion characteristics of dry sand that provides the highest level of adhesion for each level of per unit creep especially at per unit creep levels of less than 0.2. For per unit of creep levels of less than 0.05, wet sand as depicted by curve  304  provides a higher adhesion than a dry rail as shown by curve  306 . However, at per unit creep levels greater than 0.05, wet sand curve  304  has less adhesion than the dry rail curve  306 . For the situations where less adhesion is desirable, as is the case for connected railway cars or a locomotive rounding a curve in a track, oil as depicted by curve  308  provides the least amount of adhesion for per unit creep less than 0.1. Curve  310  illustrates the adhesion characteristics of water that also provides improved reduced friction as compared to a dry rail (curve  306 ) for per unit creep. From chart  300 , it is desirable to manage the friction between a wheel of a locomotive or a railway car and the railway rails in a manner that enhances the tractive effort of the locomotive while at the same time reducing the friction of railway cars connected to the locomotive. 
     Chart  400  in  FIG. 4  illustrates two changes in the operating point of a wheel on a wet rail when sand is applied to the wet rail (curve  402 ) and when sand is removed from the rail (curve  404 ). For example, if sand is applied to a wet rail at point  406  on water curve  310 , curve  402  illustrates that the creep decreases to point  408 , a point on wet sand curve  304 . Similarly, if water is applied to a rail operating at point  408  on the wet sand curve  304 , the removal of the wet sand moves the creep from point  408  to point  406  on curve  310 , thereby indicating a significant increase in creep.  FIG. 4  also illustrates optimal adhesion control system performance—creep is controlled such that maximum tractive effort is attained (assuming that the operator is calling for more tractive effort than what can be sustained by the rail conditions). Therefore, such a change can be observed by the adhesion control system only when the available adhesion at the wheel is utilized by the wheel and it typically happens at high tractive effort, low speed operating conditions. At other operating conditions the tractive effort versus creep characteristics change but not as dramatically. 
     In this illustration, a locomotive is applying 17,000 pounds of tractive effort. However, at point  406  the rail is wet and the wheels are experiencing a per unit creep of more than 0.14. Sand is applied immediately prior to the advancing wheel of the locomotive. As a result, at point  408  tractive effort is increased to 20,000 pounds and per unit creep is reduced to less than 0.03. If the sand is later removed, the operating point returns from point  408  to the prior operating point  406 . This illustrates the benefits of both applying a friction enhancing agent, in this case sand, and the subsequent removal of the sand to thereafter reduce the friction experienced by a trailing railway car. 
       FIG. 5  illustrates the tractive effort in pounds as a function of the speed of the train for eight setting tractive effort or throttle settings as denoted TE 1  to TE 8 . As shown, for a low speed there is a significant variation in the tractive effort for each of the throttle settings. However, as speed increases, the tractive effort reduces and approaches a relatively close level as the speed exceeds 50 miles per hour. It should also be noted that for each throttle setting, the tractive effort remains constant until a break speed is reached, as denoted in  FIG. 5  where each line for each tractive effort drops from the level amount to a significantly lower and decreasing amount. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Therefore, there is a need for an improved system and method for automatically controlling the application of a friction modifier to the rail by railway locomotives and cars. Such a system and method monitors and assesses various factors and parameters for the purpose of friction management and control of friction modifying agent applicators to optimize the coefficient of friction to the rail for the wheel of a locomotive and the wheel of connected railway cars. 
     One aspect of the invention comprises a system and a method for friction management is provided for managing and controlling an application of a friction modifying agent to an area of contact between a railway wheel and a railway rail over which the wheel is traversing to selectively modify the coefficient of friction at the contact area. The system comprises a sensor  610  for detecting a parameter relating to the operation of the railway train. A controller is responsive to the sensor  610  and controls the application of the friction modifying agent to the rail as a function of the parameter. An applicator is responsive to the controller and applies the friction modifying agent to the area of contact between the railway wheel and rail. 
     Another aspect of the invention comprises a method for railway train friction management for managing and controlling the application of a friction modifying agent to an area of contact between a railway wheel and a railway rail over which the wheel is traversing to selectively modify the coefficient of friction at the contact area. The method comprises sensing a parameter related to the operation of the railway train and applying the friction modifying agent to the area of contact between the railway wheel and rail as a function of the sensed parameter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a prior art locomotive having a sanding system as a friction enhancing system. 
         FIG. 2  is a schematic of the prior art sanding system of FIG.  1 . 
         FIG. 3  is an illustration of exemplary adhesion versus creep curves for different rail conditions and friction modifying agents. 
         FIG. 4  illustrates exemplary friction/adhesion curves with and without sand applied in front of an axle during wet rail conditions. 
         FIG. 5  is an exemplary graph illustrating the tractive effort in pounds in relation to the speed of the train for eight throttle settings. 
         FIG. 6  is a schematic diagram of a friction management system  600  according to the present invention. 
         FIG. 7  is a first illustration of a configuration illustrating the location of application of friction modifying agents in a first train configuration. 
         FIG. 8  is a second illustration of a configuration illustrating the location of application of friction modifying agents in a second train configuration. 
         FIG. 9  is a third illustration of a configuration illustrating the location of application of friction modifying agents in a third train configuration. 
         FIG. 10  is a fourth illustration of a configuration illustrating the location of application of friction modifying agents in a fourth train configuration. 
         FIG. 11  is an exemplary flow chart for managing and controlling the application of a friction enhancing agent to the rails according to one embodiment of the invention. 
         FIG. 12  is an exemplary flow chart for managing and controlling the application of friction reducing agent to the rails according to one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIG. 6 , the friction management system  600  according to one embodiment of the invention comprises sensors for detecting operating parameters  602  relating to the operation of the railway train. The parameters  602  are various parameters that may be indicative of the interaction between the wheels of a railway vehicle and the rails on which the railway vehicle is traversing. These parameters  602  may include operating parameters of the locomotive such as speed of the train, tractive effort (TE), throttle or notch setting, wheel speed, rate of acceleration or deceleration, braking condition, force, wheel slip/slide, fuel consumption, wheel creep, engine horsepower, and traction motor torque. These parameters  602  may be based on a per axle, per truck, or per locomotive basis. These parameters  602  are associated with the operation of the train and/or locomotive. 
     Alternatively or in addition, auxiliary information or data  604 , which may be in the form of a parameter, may be utilized as input for friction management of a railway wheel to the rail. These include consist/train length, train weight, track map, train location, track topography, track grade, track curvature, rail temperature, rail conditions such as dry, wet, rain, snow or ice, the presence of rail modifiers on a rail, both the current and forecasted weather, train schedules or external commands from operators or dispatch centers. 
     As shown in  FIG. 6 , operating parameters  602  and/or optional auxiliary data  604  are input into a controller  606 . The controller  606  may be configured to have an optional memory  608  or storage system. The controller  606  controls one or more systems for applying a friction modifying agent  612  to the rail based on the controller  606 &#39;s response to the parameters  602  and/or optional auxiliary data  604 . 
     A locomotive or a railway car is equipped with an applicator  610  that is responsive to the controller  606 . Applicator  610  applies a friction modifying agent  612  to the rail at an area of contact between the railway wheels and the rails on which they are traversing. Friction modifying agents  612  may be enhanced adhesion materials such as sand, or the removal of snow or water from the rail. Friction reducing agents may be water, steam, air, oil, a lubricant, or may be the removal of sand, water, snow or a friction enhancing agent that exists on the rail at the time. In either case, cleaning the rail with a brush, or with water or air, may be friction enhancing or friction reducing depending on the existing state of the rail. The friction management system  600  analyzes these and other operational parameters  602  and optional auxiliary data  604  to determine the appropriate timing and quantity of friction modifying agent  612  to be applied. For example, the amount of friction modifying agent  612  applied by an applicator  610  may be optimized based on the length of the train and the weather conditions such that the modifying agent  612  is consumed or dissipated by the time the last car in a train configuration passes the point of application of modifying agent  612 . While the parameters  602  and auxiliary data  604  may be used or monitored for other operational purposes, they are not used for friction management. 
     In one embodiment of the invention, a train configuration has a plurality of applicators  610  located at positions that are before the wheels of the locomotive. As a locomotive may work in the forward or reverse directions, the locomotive may be configured with friction modifying agent applicators  610  at both ends of the vehicle. Additionally, applicators  610  may be applied to the leading end or the trailing end of a locomotive or a railway car for application of a friction modifying agent  612 . 
     Applicators  610  are configured on the railway vehicle such as to enable the application of the friction modifying agents  612  to defined points of application. As such, it is contemplated that there will be a plurality of applicators  610  on each railway vehicle. Applicators  610  are configured to apply a friction modifying agent  612  to the wheel flange, the wheel rim, the top of the rail (TOR) and/or to the rail gage side (RAGS). The controller  606  determines the type, timing and quantity of the friction modifying agent  612  to be applied. The controller  606  determines the one or more applicators  610  among a plurality of applicators  610  located on a train, locomotive or railway car to apply the agent. Additionally, the controller  606  determines the point of application for the friction modifying agent  612  to be applied. 
     As noted above a plurality of applicators  610  are positioned on a locomotive and/or a railway car in order to optimize friction management of a train configuration. A train configuration is typically comprised of a lead motoring locomotive, one or more optional secondary motoring locomotives, an optional trailing motoring locomotive that is positioned in a train configuration at a point distant from the lead and secondary motoring locomotives, and one or more railway cars. The applicator, and therefore the application of friction modifying agents  612 , may be positioned as a lead applicator of the lead motoring locomotive, a trailing applicator of the lead motoring locomotive, a lead applicator of the secondary motoring locomotive, a trailing applicator of the secondary motoring locomotive, a lead applicator of the trailing motoring locomotive, a trailing applicator of the trailing motoring locomotive, a lead applicator of a railway car, or a trailing applicator of a railway car. Each of these is contemplated as being managed by the friction management system  600 . 
     The controller  606  may communicate by one or more communication systems or links (not shown) between the controller  606 , locomotives and railway cars equipped with the friction management system  600 . 
       FIG. 7  shows one embodiment of a train configuration. In configuration  1 , two locomotives, a lead motoring locomotive  702  and a secondary motoring locomotive  704 , are connected to four railway cars  706  and are moving on railway track or rail  710  in the forward direction from right to left as indicated by arrow  708 . In this case applicator  712  is an applicator that applies a friction modifying agent  612  to rail  710  prior to the wheels of the lead motoring locomotive  702 . Applicator  712  may apply a friction enhancing agent such as sand or may remove or neutralize an agent or material on rail  710 . For example, if rail  710  is wet or covered with snow or ice, and controller  606  determines that friction enhancement is required, applicator  712  may apply air to dry the top of rail  710 , or may apply steam to melt the snow or ice. Additionally, if the lead motoring locomotive  702  is entering a curved section of track, applicator  712  may apply a lubricant such as water or oil to the rail gage side of the track to reduce friction of the wheel to rail  710 . 
     The secondary locomotive  704  is configured with applicator  714  at the leading end of the locomotive  704 . The controller  606  controls the application of friction modifying agents  612  by applicator  714  based on the determined need. In some situations the controller  606  may determine that the application applied by applicator  712  on the leading locomotive  702  is sufficient for both the lead  702  and secondary  704  locomotive. This may be the case when water, snow or ice is on the track and applicator  712  is controlled to remove the water, snow or ice. However, where a steep incline is encountered, the controller  606  may control  712  and  714  to apply friction enhancing agents  612  such as sand to the top of the rail. 
     Also as shown in  FIG. 7 , applicator  716  is configured at the trailing end of the secondary motoring locomotive  704 . Applicator  716  may be configured to remove or neutralize any friction enhancing agents applied by applicators  712  and/or  714 . Furthermore, applicator  716  may apply a friction reducing agent such as air, water, oil or a lubricant to the top of the rail  710  or to the rail gage side to reduce the friction between the rail  710  and the wheels of the trailing railway cars  706 . 
     Referring now to  FIG. 8 , a second train configuration illustrates the addition of applicator  802 . Applicator  802  is located at the end of the train configuration that may be a railway car  706  as illustrated or may be a locomotive. Additionally, applicator  802  may be at the front or the rear of the last car  706  or locomotive on the train configuration. Applicator  802  is configured to remove or neutralize the friction modifying agents  612  applied earlier by applicators  712 ,  714  or  716 . This is desirable to clean the rail  710  prior to the next train configuration using the same section of rail  710 . However, the controller  606  may determine that an application of a rail cleaning agent may not be required due to the current or forecasted weather or the absence of another train to be using rail  710 . For instance, if a lubricant is applied by applicator  716 , controller  606  may determine that  802  need not apply a neutralizing agent if it is raining and another train is not scheduled to traverse the same rail  710  for an hour or more. Additionally, as noted earlier, if the controller  606  can determine the optimal amounts of friction modifying agent  612  to be applied to rail  710  by applicator  716  based on parameters  602  and auxiliary data  604  such as the length of the train and the weather conditions, the modifying agent  612  may be consumed or dissipated by the time the last car in a train configuration passes. In such cases, there will not be a need to cleanse the track by applicator  802 . 
     Now referring to  FIG. 9 , as noted earlier, railway cars  706  may be configured with applicators  610  to apply friction modifying agents  612 . Such applicators are indicated by  902  wherein any number of cars  706  may be in a train configuration and any number may be equipped with friction modifying applicators  902 . While applicators  902  configured on railway cars  706  are often friction reducers, they may be of any type. Such applicators  902  would also be controlled by the friction management system  600 , typically the same system that manages applicators  712 ,  714 ,  716 , and  802 . The friction management system  600  or controller  606  controls the application of friction modifying agents  612  to rail  710  and includes the application of friction reducing agents either to the top of the rail  710  or to the rail gage side if the train is traversing a section of rail  710  with a curve. In such an instance, the controller  606  may control the application of a friction reducing agent such as a lubricant on the inside of the rail. Furthermore, the controller  606  may only control the application of the lubricant by the applicators  610  on the rail on the side of the train which is towards the inside of the curve and not on the rail on the side on the outside of the curve. 
     Referring to  FIG. 10 , a train configuration may have a locomotive positioned remote from the lead  702  or secondary  704  locomotives. Such a trailing locomotive  1002  may be positioned at the end of the train configuration (not shown) or may be positioned in the middle of a train configuration (shown) such that railway cars  706  are positioned in front of and behind the trailing locomotive  1002 . In this embodiment of the invention, the trailing locomotive  1002  is equipped with an applicator  1004 . Applicator  1004  may apply either a friction enhancing or friction reducing agent as instructed by the controller  606 . When the controller  606  determines that a friction enhancing agent will be required to improve the tractive effort of the trailing locomotive  1002 , applicator  1004  may be instructed to remove or neutralize the friction reducing agent applied earlier by applicators  716  or  902 , and apply a friction enhancing agent such as sand. In other situations, applicator  1004  may be instructed to apply the neutralizing agent to dry the rail that increases the coefficient of friction or may be instructed to apply sand if necessary for a particular section of rail  710  or track grade. The trailing locomotive  1002  also be configured with a applicator  716  as discussed earlier. Additionally, the trailing railway cars  706  from the trailing locomotive  1002  may be equipped with applicator  802  to cleanse the rail  710  after the train has passed. 
     As discussed earlier, the controller  606  receives operating parameters  602  from one or more sensors  610  on the train, or associated with the train. Additionally, the controller  606  may also receive auxiliary data  604  from other sources that affect the management and optimization of the friction between the railway wheels and the rail.  FIG. 11  is one embodiment of a decision chart  1100  according to one embodiment of the invention. In  FIG. 11 , the train configuration is operating at a low speed and a low tractive effort has not been called  1102 . In such a case, desired tractive effort, actual tractive effort, rail condition, and slip/slide condition are determined. If the desired tractive effort in  1104  is not obtained or obtainable under the present of planned situation or condition, there is satisfactory rail conditions for the desired tractive effort  1106 , the effectiveness detection has not been disabled  1108 , and a slip or slide condition is not present  1110 , then controller  606  obtains consist or train data  1114  related to the weight of the consist, the train configuration length, an inertia estimate of the train  1116  and the rail condition  1118 . The controller  606  then determines whether friction modifying agents  612  should be applied to the rail, where to apply the agents  612 , which applicators  610  to activate for applying the agents  612 , which agents  612  should be applied and the quantity or dispensation rate  1112  of agents  612  to be applied. Controller  606  instructs at  1120  one or more applicators  610  to apply the desired agents  612 . In this case,  FIG. 11  illustrates that friction enhancing agents should be dispensed due to the need to increase the actual tractive effort to match the desired tractive effort. Once the desired tractive effort is obtained in  1104 , the process ends. Additionally, if any of the other conditions are not met such as a low tractive effort call  1102 , unsatisfactory rail condition  1106 , the effectiveness detection system is disabled  1108 , or a slip or slide condition is detected  1110 , then the process also ends. 
     As noted in  FIG. 11 , the controller  606  may determine that the conditions are such that friction enhancing agents  612  should not be applied. For instance, the controller  606  may find that the train is equipped with sand as a friction enhancer. However, the controller  606  may obtain the rail conditions that indicate that the rail  710  is wet due to rain or snow. As such, the controller  606  decides that the application of sand to a wet rail may actually reduce the tractive effort rather than increase it as shown in FIG.  4 . As such, sand would not be applied. However, the controller  606  may decide that while sand will not provide sufficient enhanced traction, that since the locomotive is equipped with an applicator for applying air to the track, that air should be applied to the rail to dry the rail  710 , thereby providing an improved friction. 
     As another example,  FIG. 12  illustrates another decision flow chart  1200  for the controller  606  in another embodiment of the invention. In this embodiment, in  1202  the tractive effort is high and a high grade does not currently exist or is not located in the track to be traversed by the train. Controller  606  receives an additional parameter that indicates that the friction is too high  1204  and that a braking operation does not exist in  1206 . If the train is operating at a speed that is not too low, a braking operation is not current  1206 , and the effectiveness detection is not disabled  1210 , controller  606  receives additional auxiliary data  604  as to the train weight, length and configuration  1114 , an estimate of the inertia of the train  1116 , and the condition  1118  of rail  710 . From this data, controller  606  determines the type, quantity, dispensation rate, and location  1112  for applying a friction reducing material  1212 . As with the prior example, the controller  606 , by receiving input from a variety of parameters  602  and auxiliary data  604 , may determine that a friction reducing agent should not be applied. For example, if the tractive effort is high or there is a high grade  1202 , if the friction is already low  1204 , if there is a braking operation  1206 , if there is a low speed operation  1208 , or if the effectiveness detection has been disabled, then the system  600  ends the process. This is illustrated in  FIG. 12  at each of the decision points going to the “End.” 
     In another embodiment, as noted above knowledge related to the length/weight/power of the consist will be applied to the determination of when and the quantity of the friction modifying agents  612  to be applied. Additionally, a track map based on a CAD system and a GPS location may be used by the controller  606  to determine when and how much and type of agent  612  to be applied. Furthermore, computer aided dispatch systems that gather and analyze train parameter information including the length of the train, weight of the train, the speed of the train and the applied power may be used as an input of auxiliary data  604  to determine when and how much friction modifying agent  612  to apply. A train scheduler/movement planner system and/or RR dispatcher to determine train characteristics are also contemplated as input to the controller  606 &#39;s determining process. 
     Another parameter  602  utilized by the friction management system  600  is an inertia estimate based on tractive effort, track grade, speed or tractive effort, GPS position, track map, and speed. The inertia of the train can be determined by the acceleration change per tractive effort change assuming the grade has not changed. If the track grade is also known, then it can be compensated for. The acceleration is obtained from the speed sensors  610  on board the locomotive, the tractive effort is the estimate of force which can be obtained typically from current and voltage measurements on the traction motors (not shown) or it could be obtained from other direct sensors  610 . The track grade could be obtained from inclinometers or could be assumed to be the same if the measurements are done over a short period of time. Another technique could use the position of the train, possibly as determined by an on-board global positioning system (GPS) receiver to obtain speed and/or track grade. Another technique could use the track map information based on GPS, operator inputs or side transponders. 
     Another parameter  602  utilized by the friction management system  600  is speed, throttle setting, and/or tractive effort. The dispensation of both high adhesion material and low adhesion material could be optimized based on the operation of the locomotive. For example, when the consist or train operator calls for high tractive effort (high notch/low speed) then only applicators  712 ,  714  and  1004  need to be enabled. If the tractive effort produced is what the operator has requested, then there is no need to add friction increasing materials. Most of the fuel efficiency benefits are at high speeds (when tractive effort is low). So under these conditions, only applicators  716  and  902  and optionally applicator  802  need to be enabled. All these variables are available easily on board the locomotive. 
     As discussed above, the condition of rail  710  is another parameter or item of auxiliary data used to determine optimal friction management. In order to optimize the cost, the dispensing of friction modifying agents  612  can be controlled based on the rail conditions. For example, if rail  710  is dry and clean, then there is no need to dispense high adhesion material. Similarly when there is rain/snow, it may not be necessary to dispense friction-lowering material since the reduction in friction may not be appreciable. Another example is if it is raining or rain is expected before the next train, then there may not be a need to remove low friction material during use of nozzle D. These rail conditions could be inferred based on sensors  610  already on board based on adhesion/creep curves, or could be based on additional sensors  610 , or inputs from the dispatch center, operators, external transponders, weather satellites etc. 
     For rail cars  706  and or idle wheels, creep could be used to estimate the friction coefficient. A separate sensor  610  could be used to determine the coefficient of friction. These sensors  610  could be placed at every point where friction lowering material dispensing is applied or at the end of the locomotive consist. Similarly friction sensors  610  or creep of the last wheel(s) may be used for dispensing neutralizing friction modifying material from applicator  802 . 
     Another factor to be considered is effectiveness detection. It is often necessary to find when these dispensing mechanisms are not working either due to failure or due to lack of friction modifying materials. This is especially important if there are many different kinds of dispensers or if it is difficult to check their operation. For example, if after dispensing high adhesion material, the creep decreases for the same tractive effort or if the tractive effort increases for the same creep or a combination is observed, then the friction modifier is effective. This could be done periodically or whenever the dispensing is initiated. Similarly when the dispensing is terminated, the opposite effect should be observed for proper operation. Similarly when the friction lowering material is dispensed there should be reduction of tractive effort required to maintain the same speed (on the same grade) or there is a speed increase for the same tractive effort. The converse should be observed when the dispensing is stopped. This checking could also be done periodically to ascertain the health of the friction lowering system. These are closed loop systems, which operate in the train. Verification of some of the effects, such as when too much friction lowering material is dispensed (see  FIG. 7 ) or when removal or neutralizing a low adhesion material is not effective (applicator  802 ), requires observation from subsequent train/locomotive which passes through the same section of track. This locomotive could observe the reduction is adhesion (compared to nominal expected) and conclude that the train ahead is malfunctioning. 
     As noted earlier, braking conditions are also factors to be considered in friction management. During a braking application, the dispensing requirement changes. No friction lowering material is required and it is advisable to increase the friction coefficient, as high braking effort is required. So during dynamic brake operation or independent brake operation only nozzles  712 ,  714 ,  1004  and possibly  802  need to operate. Nozzle  716  and  902  should not be operated. Nozzles  712 ,  714  and  1004  could be energized based on braking effort call and braking effort obtained and based on rail conditions. Similarly during train air brake operation in addition to turning off nozzles  716  and  902 , it may even be necessary to substitute it with friction enhancing material dispensers especially during emergency brake operation to reduce stopping distance. However during light braking/coasting operation friction lowering material could be dispensed if necessary to reduce wheel wear reduction and for preventing too much speed reduction. 
     During distributed power operation, the dispensing of adhesion lowering material in the lead consist depends on the number/weight of load cars between the lead consist and the trail consist (information of cars between applicators  716  and  1004  in FIG.  10 ). This information could be obtained using the distance information between the locomotives  704  and  1002 . This could be obtained from GPS position information or even using techniques like the time for brake pressure travel information. The dispensing at applicator  716  could be adjusted also based on the friction seen by the trailing locomotive  1002 . For example, if the trailing locomotive  1002  encounters very low friction, then too much material is being dispensed by nozzle  716 . 
     When introducing elements of the present invention or the embodiment(s) thereof, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
     As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.