Advantages
Multiple units have several advantages over locomotive-hauled trains:
- Energy efficiency — MUs are more energy-efficient than locomotive-hauled trains. They are more nimble, especially on gradients, as much more of the train’s weight (sometimes all of it) is carried on power-driven wheels, rather than the train having to haul the dead weight of unpowered hauled coaches. In addition, they have a lower weight-per-seat value than a locomotive-hauled train since they do not have a bulky locomotive that does not itself carry passengers, but contributes to the total weight of the train. This is particularly important where train services make frequent stops, since the energy consumed for accelerating the train increases significantly with an increase in weight.
- Higher acceleration rate — Because of the energy efficiency, higher power-to-weight ratio and higher adhesive-weight-to-total-weight ratio values, Mus generally have higher acceleration ability than locomotive-type trains and are favored in urban trains and subway (metro) systems for frequent start/stop routines.
- No need to turn locomotive — Most Mus have cabs at both ends, resulting in quicker turnaround times, reduced crewing costs, and enhanced safety. The faster turnaround time and the reduced size (due to higher frequencies) as compared to large locomotive-hauled trains, has made the MU a major part of suburban commuter rail services in many countries. Mus are also used by most rapid transmit systems. However, this is no longer a problem for locomotive-hauled trains due to the increasing use of push-pull trains.
- Makeup can be changed mid-journey — Mus may usually be quickly made up or separated into sets of varying lengths. Several multiple units may run as a single train, then be broken at a junction point into shorter trains for different destinations.
- Reliability — Due to having multiple engines, or motors, the failure of one engine does not prevent the train from continuing its journey. A locomotive-drawn train typically only has one power unit, whose failure will disable the train. However, some locomotive-hauled trains may contain more than one power unit and thus be able to continue at reduced speed after the failure of one.
The latest example of a Swiss EMU, a Siemens Desiro, on the Zűrich S-Bahn line S8
- Axle load — Multiple units have lighter axle loads, allowing operation on lighter tracks, where locomotives may be banned. Another side-effect of this is reduced track wear, as traction forces can be provided through many axles, rather than just the four or six of a locomotive.
- Easy and quick driving — Multiple units generally have rigid couplers instead of the flexible ones often used on locomotive-hauled trains. That means that brakes or throttle can be more quickly applied without an excessive amount of jerk experienced in passenger coaches.
- Allowance for accurate performance calculations for timetabling purposes — In a locomotive-hauled train, if the number of cars is increased in order to meet the demand, acceleration and braking performance drops. This calls for performance calculations to be done taking the heaviest train composition into account. This may sometimes cause some trains in off-peak periods to be overpowered with respect to the required performance. When two or more multiple units are coupled, train performance remains almost unchanged. However, in locomotive-hauled train compositions, using more powerful locomotives when a train is longer can solve this problem.
5. Answer the questions.
1. Why are multiple units more nimble on gradients?
2. Do MUs have a bulky locomotive?
3. Why do MUs have higher acceleration?
4. Why is MU a major part of suburban commuter rail services?
5. Can MU be broken into shorter trains?
6. Does the failure of one engine prevent the train from its journey?
7. What axles do MUs have?
8. What kind of couplers are typical for Mus?
9. What may cause some trains in off-peak periods to be overpowered?
10. Name the advantages of multiple units.
6. Translate the following sentences, paying attention to the Infinitive:
1. To prevent fogging of the panes and their icing in cold weather provision is made for blowing warm air over them with the aid of two fans. 2. The frame is designed to resist tensile and compressive loads up to 250 ton. 3. To upgrade the safety during railway operations to the required level, control systems are envisaged to be used for checking the suitability and reliability of the facilities and of the railway itself. 4. To ensure the timeliness of information in a great number of cases it is necessary to undertake the permanent circulation of information. 5. For semi-automatic retarding, it is necessary to install one retarder per eight tracks and radar equipment for speed changing.
7. Read the following text. Give the name to the text. Make a plan and retell the text.
In the United States in the decades after World War II, improvements in automobiles and aircraft, anti-trust restrictions on railroads, and government subsidization of highways and airports made those means practical for a greater portion of the population than previously. In Europe and Japan, emphasis was given to rebuilding the railways after the war. In the United States, emphasis was given to building a huge national interstate highway system and airports. Urban mass transport systems in the United States were largely eschewed in favor of road expansion. The U.S. railway had been less competitive as a means of transportation for several reasons: The vast size of the United States made airline travel more favorable in America, which was not an issue for the geographically smaller European countries; the government had an incentive to favor road construction as most of the world’s automobile production was in America, centered around Detroit; and the lower population density in the USA allowed easier construction of a national highway network, but mass highway construction would not have been as easy in the high population densities of the European nations and Japan. But as energy costs continue to increase, rail ridership is now increasing across the United States.
UNIT 6
maintenance – ремонт
relevance – важливість, відповідність
collision – зіткнення
shunting – маневровий
gangway – прохід
to substitute – заміняти
couchette – спальне місце (у вагоні)
supplemental – додатковий
to dedicate – призначений для чогось
density – густина
1. Match the words with their definitions.
| to substitute | devoted to a cause, ideal, or purpose |
| feature | the mass of a substance per unit volume |
| dedicated | to put or use in the place of another |
| density | something offered to the public or advertised as particularly attractive |
2. Fill in the blank spaces with:
supplemental, compared, maintenance, noise, density, add, collision, resource, replacement, evacuated.
1. The building has suffered from years of poor …. 2. The car was destroyed in the …. 3. We were surprised by the fog's …. 4. She receives a … income every month from the government. 5. We need a … for our old vacuum cleaner. 6. During World War II, children were … from London to the country. 7. I … several bicycles before buying one. 8. Oil is essentially their only …. 9. I couldn't hear him over all the …. 10. … one cup of sugar to the mixture.
3. Translate the word combinations from the text into Russian.
Self-propelled cars, the train’s power system, level-crossing accident, motive power resources, high-speed coupled sets, driving console, high population density, payload-carrying cars.
4. Read the text. Express the main idea of the text.