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Biomass Logistics
Published in Jay J. Cheng, Biomass to Renewable Energy Processes, 2017
A unit train or block train is a train that is used to move material from one point of origin to a single destination. Typically, unit trains only carry a single commodity; therefore, the railcars are usually the same type (i.e., tanker, flatbed, boxcar, etc.) if not completely identical. Unit trains are usually a predetermined length or number of railcars that is determined by the rail company that operates the railroad. In North America, the technical definition of a unit train refers to any train pulling more than 52 railcars loaded with the same commodity. However due to economic and optimization factors, unit trains are generally 75 or 110 cars in length, depending on the freight carrier. Because the unit train travels directly from the origin to the destination, shipping is fast, efficient, and runs on a tight schedule. The uniformity of the unit train system allows end users of the product being shipped to construct specialized material handling facilities that improve efficiency and economics.
U.S. railroad systems overview
Published in Richard R. Young, Gary A. Gordon, Jeremy F. Plant, Railway Security, 2017
Richard R. Young, Gary A. Gordon, Jeremy F. Plant
In selling railroad services, the freight carriers work in car units or train units. Most shippers may consign one or several carloads3 to a given customer; there are also situations where railroads sell the services of an entire train to a single customer. This occurs in two principal situations: unit trains and intermodal trains. Unit trains are where an entire train, usually hauling a single commodity, such as coal or grain, is moved from a point of origin to one destination, such as from a mine to a power plant or steel mill. Intermodal capacity is sold either as an entire train to a customer, such as UPS, or on a wholesale basis to an intermodal agent, such as Hub Group, Pacer Stacktrain, or Alliance Shippers. The character of the intermodal relationship is important because in terms of knowing what is being carried, the railroad identifies only a loaded or empty container or trailer; hence, with the exception of hazmat, it has little knowledge of the exact contents.
Common Sense Emergency Response
Published in Robert A. Burke, Common Sense Emergency Response, 2020
A unit train is a train made up of railcars transporting the same commodity throughout the entire train. Unit trains typically move from one point of origin (e.g. a shipper’s plant) to a single destination (Figure 4.19).
Numerical investigation on the aerodynamic resistances of double-unit trains with different gap lengths
Published in Engineering Applications of Computational Fluid Mechanics, 2021
Tian Li, Zhiyuan Dai, Mengge Yu, Weihua Zhang
High-speed trains are gaining more and more recognition in China for their convenience and high speed. Operating mileage continues to increase, as does passenger volume (Sun et al., 2020; Tian, 2019). However, the cost of improving passenger capacity by increasing train frequency is too high, and it may increase the safety risks associated with rail transportation (Guo et al., 2018). Therefore, a double-unit train (DUT) has become an effective way to increase passenger capacity and improve passenger transportation efficiency. The double-unit train is a special train composition in which two single-unit trains are connected to increase the length. The tail car of the first single-unit train is connected to the head car of the second single-unit train, as shown in Figure 1. The area enclosed by the streamlined part of the tail car of the first single-unit train and the head car of the second single-unit train is the double-unit region.
Study on longitudinal dynamics of heavy haul trains running on long and steep downhills
Published in Vehicle System Dynamics, 2022
Wentao Liu, Shuai Su, Tao Tang, Yuan Cao
Figure 9 shows the magnitudes of the MCF and MTF of each coupler. The MTFs of the couplers in the first unit train are generally larger than those in the second unit train. In the first unit train, the largest MTF (1948.2 kN) appears at the 78th coupler which locates in the last third portion of the first unit train. In the second unit train, the MTFs of the couplers show a decline tendency from the front to rear part. Besides, the largest MCF (2233.0 kN) in the combined HHT occurs at the second coupler of the first unit train. It is seen that the MCFs in the first and second unit train show a downward trend from the front to rear part, apart from some oscillations in the last third portion of the first unit train.
Uncertain demand based integrated optimisation for train timetabling and coupling on the high-speed rail network
Published in International Journal of Production Research, 2023
Ziyan Feng, Chengxuan Cao, Alireza Mostafizi, Haizhong Wang, Ximing Chang
Several trains run on the rail lines of the rail network. All trains can be divided into two sets: (1) existing trains that have been published on the nominal timetable and cannot be cancelled; (2) candidate trains that can be added, whose arrival and departure time at each station need to be determined. Trains are also classified into two types based on their speed limits: fast and slow. All trains are coupled with electric multiple units (EMUs). The EMU is usually formed of a set of semi-permanently coupled carriages/cars, giving so-called composition. The use of EMUs enormously increases travel efficiency, but the operation cost always stays at a high level. To alleviate the operation expenditure while ensuring service quality, trains need to be dynamically coupled/split according to travel demand. For example, high-speed trains of China Railway High-speed (CRH) can operate with fixed coupled form, precisely, 8-car EMU and 16-car EMU. Two 8-car unit trains can be coupled into a 16-car unit train, inversely, a 16-car unit train can be decoupled or split into two 8-car unit trains. Usually, the high-speed trains are coupled in terms of travel distance: short-distance trains coupled with 8-car EMU, and long-distance trains coupled with16-car EMU. After years of operation, the imbalances of capacity allocation become obvious caused by a short-term peak passenger demand on holidays or a significant decrease of off-peak passenger demand. In this paper, by taking uncertain demand into account, train coupling plans can be adjusted (to determine whether trains operate in 8-car or 16-car composition) from their origin station rather than adjusted based on the travel distances to balance capacity allocation.