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😡 BITUMINOUS MATERIALS 😡 Film thickness impacts aging processes. Dry mixtures are prone to cracking. High asphalt content and low voids may Bitumi...

😡 BITUMINOUS MATERIALS 😡 Film thickness impacts aging processes. Dry mixtures are prone to cracking. High asphalt content and low voids may Bituminous materials, commonly known as lead to pavement instability. asphalt, are viscous liquids used as binders for Improper construction, such as overheated aggregates, can prematurely age asphalt. aggregates in road construction. They can be Extended storage and climatic conditions either slightly thicker than water at normal affect binder behavior. temperature or hard and brittle. When mixed with Variability in asphalt brands impacts aggregates, bituminous materials are typically in performance consistency. High viscosity temperature ratios can liquid form. This state can be achieved by heating, cause brittleness at low temperatures. dissolving in solvents, or emulsifying in water. BITUMINOUS PAVEMENTS Bituminous materials’ action depends on the type of binder and the aggregate it is combined with, It is a combination of mineral aggregate and resisting abrasive forces from heavy traffic. binders. National Paving TYPES OF BITUMINOUS MATERIALS: Asphalt Macadam Asphalt Concrete Heated Asphalt Mastic Dissolved in Solvents Plant Mix Emulsified Asphalt Asphalt Sheet Road Mix BITUMINOUS BINDERS Armor Coat Oil Mat Asphalt cement, a semi-solid hydrocarbon, is the QUALITIES OF ASPHALT ROAD most used bituminous binder in high-quality pavements. Cutback or liquid asphalt, which 1. The surface must be free from cracks or includes asphalt cement with a liquid distillate, is traveling due to shrinkage and fatigue less favored due to fuel usability and air pollution failure. concerns. Emulsified asphalt, a mixture where 2. It must be withstanding weather condition, asphalt disperses in water, serves as an alternative including the effect of surface water, heat, to cutback asphalt, beneficial for environmental cold, and oxidation and energy considerations. Modified bituminous 3. It must be resistant to internal moisture binders like epoxy resin and bitumen-rubber such as water vapor. mixtures enhance pavement stability and 4. It must possess a tight or porous durability under specific conditions. impermeable surface as the case may be suitable to underlying base on sub-base. TYPES OF BITUMINOUS BINDERS: 5. It must be smooth riding and skid free surface. Cutback Asphalt Emulsified Asphalt THE SUCCESS OF AN ASPHALT PAVEMENT Modified Bituminous Binders LIES OR DEPENDS ON THE CONSTRUCTION QUALITY OF THE Problems Associated with Bituminous Binders: SUBGRADE, AND THE BASE COURSE. ON Several issues can affect bituminous binders' THE CONTRARY, PAVEMENT FAILURE performance: WOULD BE CONSIDERED AS A FORE-GONE BITUMINOUS PAVEMENT FAILURE CONCLUSION. Bituminous pavement failures are caused by Construction Procedures to Attain Satisfactory excessive load. Heavy load creates deflection on Asphalt Pavement the road surface, with insufficient underlying strength. ➔ Viscous asphalt binder is heated to a fluid condition and mixed with heated Repetitious application of excessive load will aggregates. The mixture is then laid and roughen and crack the road pavement that compacted while still hot. ultimately results in complete failure of the ➔ Mixing liquid or emulsion asphalt with roadway. aggregates at normal temperature is either by plant or road mixing. The mixture is Deflection on the road surface may be the effect laid compacted at normal temperature of elastic deformation from the solidation of the before the solvent evaporates or the base and subsoil or from the combination of emulsion breaks. elastic and plastic deformation. ➔ Spread and compact the clean crushed Repeated heavy wheel load on highly resilient soil stones, sprayed with heated or emulsified causes deflection leading to fatigue failure of the asphalt binder over it. Cover with sprayed asphalt surface. Alligator or map cracking of the pavement with fine aggregate. This is surface will be substantially evident. process referred to as the “penetration method.” Elastic deformation in the subgrade penetrates to a depth of 6.00 meters although mostly to a depth ASPHALT CONCRETE PAVEMENTS from the surface. The term Asphalt Concrete refers to a dense graded road surface made of hot mineral aggregates, mixed with hot asphalt and laid at Bitumen is a thick, sticky, black material made high temperatures of about 275 F to 300 F. from oil, used to hold rocks and sand together in Asphalt concrete is the highest type of dense roads, making them strong and waterproof. bituminous pavement suitable for the most heavily traveled roads. Asphalt is a mix of bitumen and small rocks or sand, used to make smooth, strong roads that can A prime coat is applied over the untreated and handle heavy traffic and rain. treated base before asphalt concrete is laid. Purpose: To bind any loose particles of the base and likewise act as a bond between the base and the pavement to deter rising moisture from penetrating the pavement. The thickness of compacted asphalt concrete ranges from 2 inches for lightly traveled roads to 6 inches or more for roads where traffic is considerably heavy. ROAD MATERIALS develop on the asphalt and water penetrate the surface until it reaches the aggregates. Aggregates Test for shape and texture - A relatively rounded Aggregates intended for either Bituminous smooth aggregate particle like natural gravel is (asphalt) or Portland cement concrete pavement, recommended for Portland cement concrete should be of good quality in accordance with the pavement because the mixture is workable. requirements of AASHTO standard or Item-703 of Meaning, easily managed and consolidated inside the Department of Public Works and Highways the forms. specifications which generally provides that: Test for resistance to polishing - One good "The aggregates shall consist of hard durable criterion for pavement design is the high particles or fragments of crushed stone, crushed coefficient of friction between the tire and the slag, or crushed rock or natural gravel." road surface. A good asphalt or concrete road design is when "the rubber tire is in direct contact Aggregates to be classified as good quality, must with the aggregate and not with the binder" undergo various test enumerated as follows: Degradation test - Some aggregates degrade in Test for strength - Los Angeles Rattler Test the presence of water. This is measured through (AASHTO T-96) mechanical agitation in water under designation test T-210 of AASHTO Test for soundness - Soundness refers to the resistance of materials to deterioration from the PARTICLE SIZE effect of action like freezing and thawing. The common test for soundness is the application with 1. For dense graded pavement. - The sodium or magnesium sulfate. (AASHTO T-104) particle size of aggregate ranges from coarse to dust. Test for affinity and swell - Strong and durable 2. For open graded pavement. - One or pavement must have binder that adhere or stick more layers of coarse rock of uniform size firmly to the aggregate particles. If the binder is used. separates or strip's-off from the aggregate, the 3. For sheet asphalt. - The mineral aggregate pavement will disintegrate under traffic. Another is a carefully graded sand and mineral reaction of the pavement is to pit when aggregates dust. are pulled-off caused by running wheels. In the event that pavement mixture swells, the interlock AGGREGATE FOR BITUMINOUS and friction between the particles are destroyed PAVEMENT resulting in collapse of the pavement stability. (AASHTO T-165) Bituminous, or asphalt, pavements rely heavily on aggregates as a primary component, making up Hydrophilic - is the term used when the aggregate 88% to 96% of the pavement by weight or over has greater affinity for water than asphalt. 75% by volume. Meaning, they like water than asphalt in contrast to hydrophobic which means fear, or against 1. Coarse aggregate materials retained on water. 2.00 mm No.lO sieve shall have a mass percent of wear by the Los Angeles Hydrophobic - the chemical bond between the Abrasion Test (AASHTO T-96) of not aggregates and water is much stronger than those more than 45 between aggregates and asphalt. On the contrary, 2. When crushed aggregate is specified, not if the aggregate is hydrophobic, pinholes will less than -50 mass percent of the particles  retained on the 4.75 mm No. a) sieve shall a. Slow curing (SC) road soil have at least one fractured face. b. Medium curing (MC) cutback 3. The fraction passing the 0.75 mm asphalt (No.200) sieve should not be greater than c. Rapid Curing (RC) cutback asphalt 213 of the fraction passing the 0.425 mm (No.40) sieve. Emulsified Asphalt 4. The fraction passing 0.425 mm (No.a0) Emulsified asphalt is a kind of mixture wherein sieve shall have a liquid limit not greater the minute globules of asphalt disperse in water. than 35 and a plasticity index. range of 4 Asphalt content ranges from 55o/o-70% by to 9 when tested by AASF{TO 'I-89 and weight. Emulsion could be applied or mixed at T-90 respectively normal temperature, because when the water BITUMINOUS MATERIALS content evaporates, the asphalt remains. It has the following characteristics. Bituminous material or Asphalt in short, is a viscous liquid used as binder for aggregates in 1. Emulsified asphalt is excellent with wet road construction. At normal temperature, asphalt aggregate because the water medium is either slightly thicker than water or hard but carries the asphalt into a superior contact brittle material that breaks under a hammer blow with the particle surfaces. when cold. 2. Emulsified asphalt is an alternate cutback asphalt for energy and environmental BITUMINOUS BINDERS objectives. It is an effective material in coating electropositive aggregate such as Asphalt cement is used as binder for almost all limestone but tends to strip from high types of bituminous pavement. Asphalt aggregates with high content of silica for cement is a semi solid hydrocarbon retained after having strong electronegative surface fuel and lubricating oils are removed from charges. petroleum. The softest grade used for pavement is 3. The Cationic Emulsion is very effective on the 200-300 penetration. The 60-70 penetrations is high siliceous aggregates but may strip the hardest type. from high alkaline that carry strong positive surface changes. Penetration refers to the consistencies of asphalt 4. Rejuvenating Agent is an emulsified cement as described under AASHTO-T49. It is the petroleum resin sprayed over the surface distance that a standard needle penetrates a sample of an old asphalt road that changes to under known conditions of loading time and asphaltenes causing the binder to harden temperature. Recently, the procedure used in and crack. The rejuvenating agent sprayed grading asphalt cement is the Viscosity Test rather over the pavement and softening the than the Penetration Test. binder. Too much application however, Cutback or Liquid Asphalt produces a slick pavement surface. 1. Liquid asphalt is a petroleum product Oxidized Asphalt and Road Tar consisting of asphalt cement with a liquid Oxidized asphalt is suitable only for roofing and distillate (diesel, kerosene or gasoline). similar applications. Highway use of oxidized The less viscous asphalt contains diluents asphalt is limited to waterproofing of structures as little as l5%. and filling joints of concrete pavement. Road tar is 2. The use of cutback is being frowned upon a by-product of the distillation process of coal. for two reasons: a. It is a usable fuel b. It is Tars are produced from gashouse coal tar, cook an air pollutant. oven tars and water gas tar. 3. Cutback or liquid asphalt is classified into: Bitumen – Rubber Mixture 4. Distillation test (AASHTO T -48) The bitumen rubber mixture for road pavement 5. Thin film oven test (AASHTO T – was experimented in Holland in the year 7929. It 179) was adopted in the United States in 1947 and later, in European countries' The assessments of the 6. Flashpoint (AASHTO T – 48%79) road states that: 7. Test for homogeneity of petroleum 1. Very little improvement gained as far as asphalt (AASHTO 102) coefficient of friction on newly laid 8. Special test for Emulsion asphalt pavement but expect higher advantages (AASHTO T-59) after six months. The analysis of the Bureau of Public Roads states that: PAVEMENT DESIGNS "An appraisal of the real economic value of the Design of Flexible Pavements addition of rubber to asphalt must wait on further observation of the behavior of experimental Structural Components of a Flexible Pavement pavements under the influence of age, weather and traffic". 2. According to the report, powdered rubber foams added to bitumen have improved the stability of some but not all. Epoxy as Bituminous Binders 1. Test of consistency is subdivided into: Subgrade (Prepared Road Bed) a. Kinematics Viscosity test The subgrade is usually the natural (AASHTO T-202) material located along the b. Saybolt-Fural test horizontal alignment of the (AASHTO T-72) pavement and serves as the foundation of the pavement c. Engler specific gravity test structure. It also may consist of a (AASHTO T 54) layer of selected borrow materials d. The float test (AASHTO T Subbase Course – 50) Located immediately above the e. Penetration test (AASHTO subgrade, the sub base component T – 49) consists of material of a superior quality to that which is generally f. Softening point test used for subgrade construction. (AASHTO T – 53) The requirements for subbase materials usually are given in terms 2. Test for durability (AASHTO T – of the gradation, plastic 52) characteristics, and strength 3. Test for solubility (AASHTO T – Base Course 44)  The base course lies immediately Portland cement is manufactured by crushing and above the subbase. It is placed pulverizing a carefully prepared mix of limestone, immediately above the subgrade if marl, and clay or shale and by burning the mixture a subbase course is not used. This at a high temperature (about 2800°F) to form a course usually consists of granular clinker. The clinker is then allowed to cool, a materials such as crushed stone, small quantity of gypsum is added, and the crushed or uncrushed slag, crushed mixture is then ground until more than 90 per cent or uncrushed gravel, and sand. of the material passes the No. 200 sieve. The main chemical constituents of the material are Surface Course tricalcium silicate (C3S), dicalcium silicate (C2S), and tetracalcium alumino ferrite (C4AF). The surface course is the upper course of the road pavement and is Coarse Aggregates constructed immediately above the base course. The surface course in The coarse aggregates used in Portland cement flexible pavements usually consists concrete are inert materials that do not react with of a mixture of mineral aggregates cement and usually are composed of crushed and asphalt. It should be capable of gravel, stone, or blast furnace slag. The coarse withstanding high tire pressures, aggregates may be any one of the three materials resisting abrasive forces due to or else a combination of any two, or all three. One traffic, providing a skid resistant of the major requirements for coarse aggregates driving surface, and preventing the used in Portland cement concrete is the gradation penetration of surface water into of the material. The material is well graded, with the underlying layers. the maximum size specified. Design of Rigid Pavements Fine Aggregates Materials Used in Rigid Pavements Sand is mainly used as the fine aggregate in Portland cement concrete. Specifications for this Portland Cement material usually include grading requirements, Coarse Aggregates soundness, and cleanliness. Standard Fines Aggregates specifications for the fine aggregates for Portland Water cement concrete (AASHTO Designation M6) give Reinforcing Steel grading requirements normally adopted by state Temperature Steel highway agencies Dowel Bars Tie Bars Water Portland Cement The main water requirement stipulated is that the water used also should be suitable for drinking. The Portland cement concrete commonly used for This requires that the quantity of organic matter, rigid pavements consists of Port land cement, oil, acids, and alkalis should not be greater than coarse aggregate, fine aggregate, and water. Steel the allowable amount in drinking water. reinforcing rods may or may not be used, depending on the type of pavement being Reinforcing Steel constructed. Steel reinforcing may be used in concrete Portland Cement pavements to reduce the amount of cracking that occurs, as a load transfer mechanism at joints, or construction (for example, between the end of one as a means of tying two slabs together. Steel day’s work and the beginning of the next). These reinforcement used to control cracking is usually joints can be divided into four basic categories: referred to as temperature steel, whereas steel rods used as load transfer mechanisms are known as Expansion Joints dowel bars, and those used to connect two slabs Contraction Joints together are known as tie bars. Hinge Joints Construction Joints Temperature Steel Expansion Joints Temperature steel is provided in the form of a bar mat or wire mesh consisting of longitudinal and are usually placed transversely, at regular transverse steel wires welded at regular intervals. intervals, to provide adequate space for the slab to The mesh usually is placed about 3 in. below the expand. These joints are placed across the full slab surface. The cross-sectional area of the steel width of the slab and are 3⁄4 to 1 in. wide in the provided per foot width of the slab depends on the longitudinal direction. size and spacing of the steel wires forming the Contraction Joints mesh. The amount of steel required depends on the length of the pavement between expansion are placed transversely at regular intervals across joints, the maximum stress desired in the concrete the width of the pavement to release some of the pavement, the thickness of the pavement, and the tensile stresses that are so induced moduli of elasticity of the concrete and steel. Hinge Joints Dowel Bars Hinge joints are used mainly to reduce cracking Dowel bars are used mainly as load-transfer along the centerline of highway pavements. mechanisms across joints. They provide flexural, shearing, and bearing resistance. The dowel bars Construction Joints must be of a much larger diameter than the wires used in temperature steel. are placed transversely across the pavement width to provide suitable transition between concrete Tie Bars laid at different times. Tie bars are used to tie two sections of the Type of Rigid Highway Pavements pavement together, and therefore they should be either deformed bars or should contain hooks to Jointed Plain Concrete Pavement (JPCP) facilitate the bonding of the two sections of the Simply Reinforced Concrete Pavement concrete pavement with the bar. These bars are Continuously Reinforced Concrete usually much smaller in diameter than the dowel Pavement (CRCP) bars and are spaced at larger centers. Typical Jointed Plain Concrete Pavement (JPCP) diameter and spacing for these bars are 3⁄4 in. and 3 ft, respectively Plain concrete pavements, which are made from a simple mixture of cement, water, and aggregate JOINTS IN CONCRETE PAVEMENTS (without any reinforcing steel), are often used in Different types of joints are placed in concrete specific situations where the traffic load and pavements to limit the stresses induced by environmental conditions are less demanding. temperature changes and to facilitate proper These pavements are typically chosen for bonding of two adjacent sections of pavement low-volume highways or areas with light traffic, when there is a time lapse between their as well as where the subbase (the layer beneath condition, delaying repairs can lead to more the concrete) is made of cement-stabilized soil. extensive damage and higher rehabilitation costs. Pavement deterioration is typically caused by Simply Reinforces Concrete Pavement factors such as climate, drainage issues, soil conditions, and heavy truck traffic, rather than have dowels for the transfer of traffic loads across poor design or construction. Limited budgets force joints, with these joints spaced at larger distances, agencies to prioritize between preventive ranging from 30 to 100 ft. Temperature steel is maintenance, which is cost-effective but often used throughout the slab, with the amount neglected, and corrective actions for critical dependent on the length of the slab. Tie bars also defects. are used commonly at longitudinal joints. Approaches to Pavement Management Continuously Reinforced Concrete Pavement (CRCP) The term pavement management describes the various strategies that can be used to decide on a have no transverse joints, except construction pavement restoration and rehabilitation policy. joints or expansion joints when they are necessary These strategies range from addressing issues as at specific positions, such as at bridges. These they arise (a "squeaky wheel" approach) to pavements have a relatively high percentage of maintaining all roads on a regular, unrestricted steel, with the minimum usually at 0.6 percent of budget. Practical pavement management plans set the cross section of the slab. They also contain tie minimum standards for road conditions, determine bars across the longitudinal joints. necessary treatments, and establish timelines, Pumping of Rigid Pavements balancing factors like pavement condition, initial costs, maintenance, user expenses, safety, and Pumping is an important phenomenon associated environmental impacts. with rigid pavements. Pumping is the discharge of water and subgrade (or subbase) material through Life-cycle cost analysis is fundamental in joints, cracks, and along the pavement edges. It pavement management, covering the total project primarily is caused by the repeated deflection of cost from initial construction to major the pavement slab in the presence of accumulated rehabilitation. Pavement management aims to water beneath it. The mechanics of pumping can maintain, improve, and operate pavement assets best be explained by considering the sequence of systematically and cost-effectively by integrating events that lead to it. engineering principles with economic practices. Visual manifestations of pumping include: Key Steps in Pavement Management Discharge of water from cracks and joints Step 1: Assess Present Pavement Condition Spalling near the centerline of the Step 2: Predict Future Condition pavement and a transverse crack or joint Mud boils at the edge of the pavement Step 3: Conduct Alternatives Analysis Pavement surface discoloration (caused by the subgrade soil) Step 4: Select Appropriate Rehabilitation Strategy Breaking of pavement at the corners Elements of the Pavement Management System Problems of Highway Rehabilitation Inventory and Condition Database Highway and transportation agencies frequently Mathematical Models for Forecasting struggle with insufficient funding, which limits Procedures for Alternative Analysis their ability to repair all deteriorating roadways. Reporting and Visualization Tools Although some roads remain usable despite poor Methods for Determining Roadway Condition diesel engine’s high efficiency makes it suitable as a locomotive prime mover, providing reliable 1. pavement roughness (rideability) power across variable operational needs. 2. pavement distress (surface condition) 3. pavement deflection (structural failure) Electric Transmission Equipment 4. skid resistance (safety). In diesel-electric locomotives, a generator Pavement Rehabilitation or alternator directly coupled to the engine provides power, with its output controlled A variety of methods can be used to rehabilitate by engine speed and field adjustments. pavements or to correct deficiencies in a given pavement section including using overlays, Electrical Controls sealing cracks, using seal coats, and repairing potholes. In conventional DC propulsion systems, contactors control the connection between Rehabilitation Techniques and Strategies traction motors and the main generator, Rehabilitation techniques are classified as: with interlocks for safety and operation, and a cam switch is used for reversing and 1. corrective, which involves the permanent dynamic braking. or temporary repair of deficiencies on an as-needed basis CABS 2. preventive, which involves surface applications of either structural or The AAR sets uniform safety standards for nonstructural improvements intended to locomotive cab features, including noise keep the quality of the pavement above a and control systems, to ensure safe predetermined level. operations. Pavement rehabilitation strategies can be Batteries categorized in a variety of ways. Diesel locomotives commonly use One approach is in terms of the problem lead-acid batteries, typically with 280 or being solved, such as skid resistance, 420 ampere-hour capacity, to start the surface drainage, unevenness, roughness, engine. Each unit has 32 cells, supplying or cracking. 64 volts to the system, and the batteries are Another approach is in terms of the type of recharged from a 74-volt power source. treatment used, such as surface treatment, AIR-BRAKES overlay, or recycle. A third approach is in terms of the type of The engineer controls locomotive braking surface that will result from the process, with two brake valve handles: the such as asphalt overlay, rock seal coat, or "independent" for the locomotive alone liquid seal coat. and the "automatic" for the entire train. Dynamic Braking DIESEL – ELECTRIC LOCOMOTIVES Dynamic brakes convert locomotive kinetic energy into heat, dissipated through Diesel-electric and electric locomotives are resistance grids cooled by motor-driven classified by wheel arrangements using letters for fans. This system, controlled by adjusting driving axles in a truck (e.g., "B" for two axles motor excitation and grid resistance, and "C" for three), and numerals for idler axles, with additional symbols for articulation. The  supplements air brakes and reduces wear, Maximum Speed - Traction motors are also rated especially on long grades in terms of their maximum safe speed in r/min, which in turn limits locomotive speed. PERFORMANCE Locomotive Compatibility - The AAR has Engine-Indicated Horsepower - the theoretical developed two standards in an effort to improve power of a reciprocating engine if it is completely compatibility between locomotives of different frictionless in converting the expanding gas model, manufacture, and ownership: a standard energy 27-point control system and a standard control stand. Rail Horsepower - a measurement of how much power an engine can produce after accounting for Energy Conservation - Efforts to improve frictional losses efficiency and fuel economy have resulted in major changes in the prime movers, including Thermal Efficiency - The thermal efficiency of more efficient turbocharging, fuel injection, and the diesel engine at the crankshaft, or the ratio of combustion. bhp output to the rate at which energy of the fuel is delivered to the engine, is about 33 percent. Emissions - The U.S. Environmental Protection Thermal efficiency at the rail is about 26 percent. Agency has promulgated regulations aimed at reducing diesel locomotive emissions, especially Drawbar Horsepower - The drawbar horsepower oxides of nitrogen (NOx). These standards also represents power available at the rear of the include emissions reductions for hydrocarbons locomotive to move the cars. (HC), carbon monoxide (CO), particulate matter Speed-Tractive Effort - The tractive effort of a (PM), and smoke. diesel-electric locomotive varies with speed, ELECTRIC LOCOMOTIVES following a nearly hyperbolic curve. At full throttle, the locomotive provides full horsepower Electric locomotives in North America are mostly across the speed range, but power decreases as the used for coal or mineral freight and in speed approaches its limit, a process called high-density passenger service in the northeastern "power matching." This enables multiple U.S. They draw power from overhead catenary or locomotives with different power ratings to third-rail systems, with newer systems using operate together at the same speed. 25,000 or 50,000 V at 60 Hz. Adhesion - Adhesion, typically 25% of the Report on Passenger Rail Equipment Types locomotive's weight on drivers, determines tractive effort, but it can vary from 5% to 35% Over the past two decades, passenger rail services depending on rail conditions. Lubricants reduce in North America, especially for long-distance adhesion, but sand from the locomotive can routes, have largely been managed by government improve it. AC traction motors can achieve higher agencies like “Amtrak” in the U.S. and “Via Rail” adhesion levels, up to 45% at low speeds, with a in Canada. Passenger rail equipment for “urban nominal value of 35%. transit” is divided into three main categories: commuter rail, heavy rail rapid transit (HRT), and Traction Motor Characteristics - Motor torque light rail transit (LRT). These categories depend in traction motors depends on motor current, on the characteristics of the service, such as the which determines tractive effort, with field type of infrastructure and traffic conditions. shunting altering this relationship at certain levels. Main-Line Passenger Equipment Main-line passenger trains are used for long-haul These trains are built to handle sharp curves, high services. There are four primary types of speeds (up to 75 mph), and frequent stops, with main-line train sets: acceleration rates between 2.5 to 3.0 mph/sec. They also have robust braking systems, including Diesel Locomotive-Hauled Trains dynamic braking and electro-pneumatic friction Diesel Multiple Units (DMU) brakes, to ensure fast and safe stops Electric Locomotive-Hauled Trains Electric Multiple Units (EMU) Light Rail Transit (LRT) Equipment Trains are equipped with advanced suspension Light rail transit (LRT) is a versatile and systems to ensure a smooth ride, including: flexible rail system used in cities like San Diego, Portland, and Calgary. LRT systems can run on a Primary Suspension: Isolates the wheels from mix of surface streets, dedicated tracks, or even the truck using coil springs, elliptical springs, or elevated lines. Key features of LRT equipment elastomeric components. include: Secondary Suspension: Isolates the truck from Light Rail Vehicles (LRVs): These cars the car body using large coil rings or pneumatic are electrically powered, usually via springs, with hydraulic dampers to improve ride overhead catenary wires. They range in quality size from 60 to 90 feet and are often articulated to carry more passengers while Commuter Rail Passenger Equipment being able to navigate tight curves. Commuter rail operates in urban or suburban Braking Systems: LRTs use a areas, providing services to and from city centers. combination of dynamic, friction, and There are two types of commuter rail equipment: track brakes. The dynamic braking helps slow down the train during regular Locomotive-Hauled operation, while track brakes are used in Self-Propelled Units (e.g., DMUs) emergencies. Passenger Capacity: LRT cars typically Commuter rail trains often use push-pull have 50 to 80 seats, but the total capacity operations, where the locomotive can either push is much higher when factoring in standing or pull the train. Some cars are equipped with cabs room. at both ends, allowing the engineer to operate the train from either direction. Automatic couplers are VEHICLE-TRACK INTERACTION AND used to link cars together, with most commuter TRAIN RESISTANCE rail cars using AAR-type couplers. Types of Train Resistance Heavy Rail Rapid Transit Equipment Inherent Resistance includes rolling Heavy rail rapid transit systems are found in resistance at low speeds and aerodynamic major cities like New York, Chicago, and Boston, resistance at high speeds. At higher and they operate on dedicated tracks (subways or speeds, aerodynamic resistance dominates, elevated lines). These systems use: and it decreases with increased car weight. Incidental Resistance arises from factors - Electric Propulsion (usually from a third rail or like track grade, curvature, wind, and pantographs). vehicle dynamics, all affecting the train’s performance - Bidirectional Operation with up to 12 connected cars. Key Resistance Components  Rolling Resistance: Significant at low Association of American Railroads (AAR) has speeds, decreases with car weight. established design and maintenance criteria to Aerodynamic Resistance: Dominates at assure the interchangeability of freight cars on all higher speeds, independent of car weight, North American railroads and increases with speed. Wind Resistance: Affected by vehicle AAR - The AAR Manual of Standards and design, open tops, protrusions, and vehicle Recommended Practices specifies dimensional spacing. limits, weights, and other design criteria for cars Curve Resistance: Increases with the that may be freely interchanged between North degree of curvature. Rail lubrication and American railroads. special truck designs can reduce friction The AAR identifies most cars by nominal capacity and resistance. and type, and in some cases there are restrictions Grade Resistance: Related to the incline or as to type of load (i.e., food, automobile parts, coil decline, calculated as 20 lb/ton per 1% steel, etc.). Most modern cars have nominal grade. capacities of either 70 or 100 tons. Acceleration Resistance: Force required to accelerate the train, including both linear Boxcars and rotational components. 1. Standard boxcars may have Vehicle Suspension System either sliding or plug doors. Plug doors provide a tight seal from Designed to isolate track input forces from weather and a smooth interior. the car body and prevent instability such as Unequipped box cars are usually of harmonic roll, pitch, bounce, and yaw. 70-ton capacity. These cars have Advances in suspension design reduce tongue-and-groove or plywood undesirable behaviors and enhance lining on the interior sides and ends performance. with nailable floors (either wood or Superelevation steel with special grooves for locking nails). Superelevation compensates for centrifugal force during curve negotiation by raising the outside 2. Specially equipped boxcars rail. The maximum allowable superelevation for usually have the same dimensions freight trains is usually 6 inches, adjusted for train as standard cars but include special speed and curve radius. interior devices to protect lading from impacts and over-the-road Longitudinal Train Action vibrations. Specially equipped cars may have hydraulic-cushion units Slack action refers to the dynamic forces between to dampen longitudinal shock at the individual cars in a train, which can cause couplers. instability or breakage under certain conditions. Analysis of longitudinal forces and tractive effort 3. Insulated boxcars have plug is essential to minimize these effects. doors and special insulation. These cars can carry foodstuffs such as FREIGHT CARS unpasteurized beer, produce, and dairy products. These cars may be Freight Car Types precooled by the shipper and Freight cars are designed and constructed for maintain a heat loss rate equivalent either general service or specific ladings. The to 1F (0.55C) per day  4. Refrigerated boxcars are used typical 100-ton coal hopper car will vary in where transit times are longer. volume depending on the light weight of the car These cars are equipped with and density of the coal to be hauled. Volumes diesel-powered refrigeration units range from 3,900 to 4,800 ft3 (110 to 136 m3 ). and are primarily used to carry fresh produce and meat. They are High-side Gondola Cars often 100-ton cars. High-side gondola cars (Figure 23.14d) are 5. ‘‘All-door’’ boxcars have doors open-top cars typically used to haul coal or wood that open the full length of the car chips. These cars are similar to open-top hopper for loading package lumber cars in volume but require a rotary coupler on one products such as plywood and end for rotary dumping to discharge lading since gypsum board. they do not have bottom outlets. Rotary-dump coal gondolas are usually used in dedicated, 6. High-cubic-capacity boxcars unit-train service between a coal mine and an with an inside volume of 10,000 ft3 electric power plant. The length over coupler (283 m3) have been designed for pulling faces is approximately 53 ft 1 in. (16.2 m) light-density lading, such as some to suit the standard coal dumper. automobile parts and low-density paper products. Bulkhead Flat Cars Boxcars Bulkhead flat cars are used for hauling such commodities as packaged finished lumber, pipe, Boxcar door widths vary from 6 to 10 ft for or, with special inward canted floors, pulpwood. single-door cars and 16 to 20 ft (4.9 to 6.1 m) for Both 70- and 100- ton bulkhead flats are used. double-door cars. All-door cars have clear Typical deck heights are approximately 50 in. doorway openings in excess of 25 ft (7.6 m). The (1,270 mm). floor height above rail for an empty uninsulated boxcar is approximately 44 in. (1,120 mm) and for Tank Cars an empty insulated boxcar approximately 48 in. Tank cars are used for liquids, compressed gases, (1,220 mm). The floor height of a loaded car can and other ladings, such as sulfur, that can be be as much as 3 in. (76 mm) lower than the empty loaded and unloaded in a molten state. car Nonhazardous liquids such as corn syrup, crude Covered Hopper Cars oil, and mineral spring water are carried in nonpressure cars. Cars used to haul hazardous Covered hopper cars are used to haul bulk substances such as liquefied petroleum gas (LPG), commodities that must be protected from the vinyl chloride, and anhydrous ammonia are environment. Modern covered hopper cars are regulated by the U.S. Department of typically 100-ton cars with roof hatches for Transportation loading and from two to six bottom outlets for discharge. Cars used for dense commodities, such Intermodal Cars as fertilizer or cement, have two bottom outlets, Boxcar door widths vary from 6 to 10 ft for round roof hatches, and volumes of 3,000 to 4,000 single-door cars and 16 to 20 ft (4.9 to 6.1 m) for ft3 (84.9 to 113.2 m3 ). double-door cars. All-door cars have clear Open-top Hopper Cars doorway openings in excess of 25 ft (7.6 m). The floor height above rail for an empty uninsulated Open-top hopper cars are used for hauling bulk boxcar is approximately 44 in. (1,120 mm) and for commodities such as coal, ore, or wood chips. A an empty insulated boxcar approximately 48 in. (1,220 mm). The floor height of a loaded car can Lading Restraint Systems: From tie-downs be as much as 3 in. (76 mm) lower than the empty for vehicles to bulkheads for pulpwood, car these features secure cargo effectively. Intermodal Adaptations: Well cars enable Design Standards and Safety double-stacked containers, significantly increasing freight capacity. Weight and Dimensions: For example, modern cars handle up to 100 tons, with RAILWAY TRACK DESIGN axle journals designed for high durability. Structural Integrity: Freight cars must Track Components withstand extreme loads, such as coupling impacts reaching 1.25 million pounds. Superstructure: Safety Features: These include compliance Rails: Guide wheels, transfer loads, resist with the Safety Appliances Act and Power temperature-induced stresses. Brake Law, ensuring brake efficiency and Fastening Systems: Secure rails to ties, prevention of derailments. provide stability. Suspension Systems Crossties: Distribute loads, maintain rail alignment. Side Frames and Bolsters: These components provide structural support Substructure: while allowing flexibility. Ballast: Provides drainage, stability, and Spring Damping: Springs with friction adjusts track geometry. wedges or hydraulic dampers enhance ride Subballast: Separates ballast from quality and minimize wear. subgrade, improves resilience. Steering Features: Some advanced trucks Subgrade: Foundation layer that provides improve lateral stability and reduce overall stability curving resistance, contributing to smoother operations. Track Forces Braking Systems Vertical Forces: Air Brakes: Standard in North America, Generated by train weight; impact rail and these use a brake pipe to control the air ballast integrity. pressure and apply force to brake shoes, ensuring consistent braking across the Lateral Forces: train. Dynamic Brakes: Locomotives equipped Due to curves and temperature changes; with these brakes use traction motors as can lead to rail buckling. generators to control speed. Longitudinal Forces: Advanced Cushioning: Hydraulic systems reduce coupling forces and prevent Caused by train acceleration, braking, and damage to cargo during impacts. thermal expansion/contraction. Special Features Track Design Considerations Coupler Cushioning: This reduces impact Vertical Track Stiffness: forces during yard operations, protecting cargo. Ensures adequate load distribution across components.  Lateral Stability: 3. Transfer wheel loads to spaced ties without large deflection. Prevents buckling through proper ballast 4. Resist tension failure from longitudinal compaction and geometry. tensile force caused by rail temperature reduction. Drainage Systems: 5. Help resist buckling from longitudinal Removes water to maintain track integrity compression force caused by rail temperature and prevent fouling. increase. 6. Resist fatigue cracking from repeated wheel loads. 7. Provide strong bolted or welded joints. 8. Limit rail impact by maintaining track geometry and truing wheels to limit ‘‘false flange’’wear on wheel and rail and reduce wheel defects such as engine burns, corrugations, and flat spots. 9. Permit tracks to cross over each other and permit trains to switch from one track to another. Fastening Systems 1. Restrain the rail in the vertical, longitudinal, and transverse directions. 2. Resist overturning of rail from lateral wheel force. 3. Connect sections of rail to permit safe and smooth train operation. 4. Create a canted (inclined) surface to provide proper wheel/ rail contact—wood ties. 5. Spread the rail seat force over a larger part of the tie surface to reduce the damage—wood ties. 6. Provide resiliency under the vertical wheel Railway Track Design load—concrete ties. 7. Reduce tie abrasion trail seat—concrete ties. 🙁 consists of superstructure and substructure. The 8. Provide damping of the high frequency superstructure is composed of steel rails fastened to wheel-induced vibrations—concrete ties. crossties. The rails are designed to support and guide Crossties flanged steel wheels through their prescribed position in space. 1. Transfer the vertical wheel load from the rail through the rail seat to the bottom of the ties to FUNCTIONS OF TRACK COMPONENTS provide an acceptable level or stress for the ties and ballast. Rails 2. Hold the fastening system so that it can 1. Guide the flanged wheels in the vertical, restrain the rails at the proper vertical, lateral, letter l, and longitudinal directions. and longitudinal position and maintain the 2. Provide a smooth running surface. required gage.  3. Provide a canted (inclined) surface for proper Drainage wheel / rail contact—concrete ties. Drainage is the single most important factor Ballast governing the performance of track substructure. A properly functioning drainage 1. Restrain the ties against vertical, lateral, and system provides the following: longitudinal forces from the rails. 2. Reduce the pressure from the tie-bearing area 1. Intersects the water seeping up from the to a level that is acceptable for the under- lying subgrade materials. 2. Diverts the surface water flowing toward the 3. Provide the ability to adjust track geometry track by rearranging the ballast particles by tamping 3. Removes water falling onto the track and lining. 4. Carry off stone dust, sand, and other debris that 4. Assist in drainage of water from the track. otherwise could foul the track. 5. Provide sufficient voids between particles to allow an efficient migration of unwanted fine Track Forces particles from the ballast section. The forces applied to the track are vertical, lateral 6. Provide some resiliency to the track to decrease (parallel to the ties), and longitudinal (parallel to rail, rail component, and wheel wear. the rails). These forces are affected by train travel speed. Subballast 1. Maintain separation between the ballast and Vertical subgrade particles. The main vertical force is the repetitive downward 2. Prevent attrition of the hard subgrade surface by action of the wheel load. In addition, this wheel/ the ballast. rail interaction produces a corresponding lift-up force on the ties away from the wheel load points. 3. Reduce pressure from the ballast to values that can be sustained by the subgrade without The major factors affecting the magnitude of the adverse effects. dynamic vertical forces are: 4. Intercept water from the ballast and direct it to Nominal wheel load the track drainage system. Train speed 5. Provide drainage of water flowing upward from Wheel diameter the subgrade. Vehicle unsprung mass 6. Provide some insulation to the subgrade to Smoothness of the rail and wheel surfaces prevent freezing. Track geometry 7. Provide some resiliency to the track. Track modulus or vertical track stiffness Subgrade Lateral 1. Provide a stable platform on which to construct One type of lateral force applied to the rail is the the track. wheel force transmitted through friction 2. Limit progressive settlement from repeated between the wheel and top of the rail and by the traffic loading. wheel flange acting against the inside face of the 3. Prevent massive slope failure. rail head, particularly on curves. Another lateral force is the rail buckling resistance force. 4. Restrict swelling or shrinking from water content change. The design lateral wheel force depends upon a number of factors, including:  Vehicle speed Track geometry Elevation difference between the two rails at the same cross section Transverse hunting movement due to the train-track dynamics Longitudinal Sources of longitudinal rail forces are: Speed Locomotive traction Locomotive and car braking Expansion and contraction of the rails from temperature change Track grade Special track, i.e., turnouts, at grade crossings, rail crossings, dragging equipment, hot bearing detectors The ratio of lateral to vertical force (L / V) is also important because it can cause loss of alignment and even track buckling. Track Systems Characteristics Track system performance is a function of the composite response of the track components under the action of the train loads. Two response characteristics are important to consider in track design: vertical track stiffness and lateral track stability. Made with with love - shan and tel 💗 KAPOYYY NAAA!!!!