|
|
|
|
|
|
|
|
General information
|
|
|
|
|
|
|
|
|
|
|
Description
|
|
|
|
|
|
Since in MUs the traction components are distributed along the train, the
cars of a given set cannot be decoupled. This tends to reduce flexibility of
train length. On the other hand, short train-sets can be ordered in order to
recover some of the modilarity in train formation typical for loco-hauled train
operation.
Need for trains with variable length
Short train-sets offer two main benefits:
- Capacity can be adapted to variable demand (e.g. rush-hour vs. late
evening in suburban transport)
- Trains can split up in two train-sets at a certain point of the route to
serve two destinations. Passengers do not have to change trains and the
operator saves costs.
Realisations
- Short MUs: MUs are ordered as short train-sets (e.g. two-car sets) and can
then be combined to double or triple trains for times or routes with high
demand. This concept is especially suited to local and suburban service where
no passenger mobility along the whole train is needed.
- MUs are ordered in different lengths. For example DB AG ordered the ICE T
tilting trains in two lengths: 5-car and 7-car train-sets. Despite higher
seat-specific investment costs, this can be interesting in main-line service
where passenger mobility along the whole train is required.
- IC3 type: A special case is the Danish IC3 concept (with its
characteristic rubber frames at both ends of a train-set). The train sets are
short (3-car units) but can be easily coupled to longer trains without
limiting passenger mobility along the train. This is achieved by a special
design allowing to fold away the driver cabins in order to create regular car
transitions for passengers.
- ICE 2 type: The typical configuration of a German ICE 2 consists of two
half trains each having a locomotive at one end and a small driving unit
(without installed power) at the other end. This allows for a splitting up of
the ICE 2 in two half trains in order to serve two routes having the first
part of the trip in common (for example the Berlin-Cologne
line).
|
|
|
General criteria
|
|
|
|
|
|
|
|
|
|
|
Status of development: in use |
|
|
|
|
|
(no details available) |
|
|
|
|
|
|
|
|
Time horizon for broad application: now |
|
|
|
|
|
There are increasing efforts in railways to flexibilise the MU concept. |
|
|
|
|
|
|
|
|
Expected technological development: dynamic |
|
|
|
|
|
Size and costs of traction equipment
The development of cost efficient EMUs was made possible by a substantial
reduction of the size of traction equipment allowing for a decentralised
under-floor lay-out. Advances in traction technology (e.g. medium-frequency
transformers) could drive this trend even further. However, two short
train-sets are more expensive than one long train-set since two entire power
trains are installed. This effect could be reduced if cheaper power electronics
or transformers become available. |
|
|
|
|
|
|
|
|
Motivation:
|
|
|
|
|
|
Raised load factors and thus better utilisation of stock. |
|
|
|
|
|
|
|
|
Benefits (other than environmental): medium |
|
|
|
|
|
Cost efficiency of passenger operation. |
|
|
|
|
|
|
|
|
Barriers: medium |
|
|
|
|
|
Investment costs
Increased seat-specific costs, cf. Economic criteria vehicle fix costs.
Coupling
Adapting train length to actual demand increases the train formation costs
due to coupling processes.
Passenger mobility
In main-line service, passenger mobility along the train plays an important
role (e.g. to access dining-car etc.). If train is composed of several
train-sets coupled together, this mobility is limited. |
|
|
|
|
|
|
|
|
Success factors:
|
|
|
|
|
|
Passenger mobility along the train
In main line service, passenger mobility plays an important role for service
quality. A joint effort between railways and manufacturers could generate
satisfying solutions involving coupled train-sets with passenger transitions
between the sections. The Danish IC3 shows that such solutions are not
altogether impossible. |
|
|
|
|
|
|
|
|
Applicability for railway segments: high |
|
|
|
|
Type of traction: electric - DC, electric - AC, diesel
|
|
|
|
|
Type of transportation: passenger - main lines, passenger - high speed, passenger - regional lines, passenger - suburban lines, freight
|
|
|
|
|
|
(no details available) |
|
|
|
|
|
|
|
|
Grade of diffusion into railway markets:
|
|
|
|
|
Diffusion into relevant segment of fleet: not applicable |
|
|
|
|
Share of newly purchased stock: not applicable |
|
|
|
|
|
(no details available) |
|
|
|
|
|
|
|
|
Market potential (railways): high |
|
|
|
|
|
(no details available) |
|
|
|
|
|
|
|
|
Example:
|
|
|
|
|
|
(no details available) |
|
|
Environmental criteria
|
|
|
|
|
|
|
|
|
|
|
Impacts on energy efficiency:
|
|
|
|
|
Energy efficiency potential for single vehicle: > 10% |
|
|
|
|
Energy efficiency potential throughout fleet: 2 - 5% |
|
|
|
|
|
The energy efficiency potential offered by flexible train-sets is difficult
to assess in general terms. It depends on spatial and temporal demand variation
and train design.
Example
The following (simplified) example may give an idea of the different
influencing factors:
On a given line presently operated with 4-car train-sets, 50% of the runs
have an average occupancy of 80%, the other 50% only 30%. If 2-car train-sets
are introduced instead, 50% of the runs will be realised with two 2-car
train-sets coupled together, the rest with only one 2-car set. The energy
consumed for all the runs will be referred to as 100%.
A typical situation in suburban transport is assumed with the following
components of energy consumption:
- 30% air drag
-
- 50% acceleration
- 20% comfort functions
Energy balance for times with high occupancy: Using two coupled 2-car sets
rather than one 4-car set slightly (< 10%) increases the mass due to more
traction equipment. A 10% mass increase will increase energy consumption by
about 5%.
Energy balance for the rest of the day: Using a 2-car rather than a 4-car set
during hours of low-demand reduces energy demand due to 3 effects:
- Energy demand for comfort functions is reduced by ~50% (=10% of the total
consumption)
- With one train set instead of two and 10% higher mass per car (cf. above),
mass is reduced by ~45% (=22,5 % of total energy demand)
- Due to reduced train length, air drag is reduced by ~30% (=9% of total
energy demand).
Aggregating these data, we get the following energy balance through the use
of shorter units:
- Runs during high-demand period consume 5% more energy.
-
- Runs during low-demand period consume ~41,5 % less energy
- Assuming that 50% of the energy is consumed on 50% of the runs if the same
train-sets are used for all runs, one gets a total energy savings of 0,5 ?
41,5% - 0,5 ? 5% = 18%.
Conclusion
The above example simplifies the real situation. It shows however, that an
energy saving potential of over 10% is realistic. |
|
|
|
|
|
|
|
|
Other environmental impacts: positive |
|
|
|
|
|
Flexible train-sets reduce the total rolling stock needed to supply a given passenger transport volume. This improves the overall resource efficiency of passenger operation. |
|
|
Economic criteria
|
|
|
|
|
|
|
|
|
|
|
Vehicle - fix costs: medium |
|
|
|
|
|
The seat-specific costs are higher for shorter units since (almost) the same transformer and inverter equipment is needed as for a longer unit. The same is true for the drivers’ cabins. An additional cost effect can arise if trains-sets of different length are ordered, especially if the train design requires a tailored solution, as was the case for 5-coach and 7-coach MUs ordered for the ICE T tilting trains.
However, the increase in seat-specific investment costs will in most cases be overcompensated by less need for seating capacity due to better adaptation of capacity to demand. |
|
|
|
|
|
|
|
|
Vehicle - running costs: significant reduction |
|
|
|
|
|
The running costs per passenger-km are substantially reduced due
to
- Reduced energy consumption
- Reduced maintenance costs (less rolling stock
required)
|
|
|
|
|
|
|
|
|
Infrastructure - fix costs: none |
|
|
|
|
|
(no details available) |
|
|
|
|
|
|
|
|
Infrastructure - running costs: increased |
|
|
|
|
|
More coupling and decoupling processes are required for train formation. |
|
|
|
|
|
|
|
|
Scale effects: low |
|
|
|
|
|
(no details available) |
|
|
|
|
|
|
|
|
Amortisation: strongly dependent on specific application |
|
|
|
|
|
(no details available) |
|
|
Application outside railway sector (this technology is railway specific)
|
|
|
Overall rating
|
|
|
|
|
|
|
|
|
|
|
Overall potential: promising |
|
|
|
|
Time horizon: short-term |
|
|
|
|
|
Short train-sets are an effective means to achieve a better occupancy in situations with strong variation of temporal or spatial demand. This reduces costs and improves energy efficiency (per passenger-km) considerably. Higher seat-specific investment is compensated by reduced seating capacity to be supplied. In local and regional service the use of short MUs to adapt train length to demand is already wide-spread. However, some operators fear higher complexity of train formation processes and additional planning efforts to ensure vehicle availability. In main line service, a major barrier lies in the reduced mobility of passengers along the train. A joint effort between railways and manufacturers could generate satisfying solutions for this problem. |