Principle

Conventional stock for long-distance and regional service has an exterior coach width of around 2900 mm. In an effort to increase floorspace per coach, trains have been developed that are considerably wider. For our purposes, we define a wide-body train as one allowing a 2 3-seating arrangement in 2nd class and a 2 2- arrangement in 1st class. In main line service this usually requires a minimum width of about 3300 mm. The gain in floorspace is in the order of 10 to 20%. Considerations of the DB AG for a wide-coach version of the ICE 4 indicate an increase in seating capacity of 22% compared to the "normal" version (as opposed to slightly less for a double-decked version).

Examples

The following table lists some wide-body trains.

Source: Andersson et al. 2001

• The Lirex developed by Alstom shows that at least for regional service 5-seat arrangements can be integrated in coaches which are only 3042 mm wide.
• An example of extremely wide coaches (3600 mm) is the Copenhagen suburban train set produced by a Siemens/LHB consortium. Many German suburban trains have a width of about 3200 mm.
• In Japan there are also some 3.40 meter wide Shinkansen trains which are double-deckers. In some of their coaches there are 2 3 seats downstairs and 3 3 seats upstairs. Such a seat arrangement of course gives a significant reduction of comfort.

Infrastructural compatibility

As opposed to isolated solutions (e.g. suburban networks), mainline service sets more rigorous conditions to stock width, especially if interoperability is demanded. However some conceptional and technological measures could raise infrastructural compatibility of wide-body stock. Among them are reduced coach length (thus reducing the lateral swinging out in curves) and more high tech solutions such as a telematically controlled tilting away from infrastructural obstacles.

Infrastructure compatibility

On some of the tracks presently not allowing wide-body stock, infrastructural compatibility could be reached by various technological measures concerning the stock rather than the track:

• by ensuring an increased stability of the coach body against lateral swaying in narrow parts of the track.
• by an active suspension reducing the lateral spring travel and thus allowing a further 50 - 70 mm of car-body width within the same car-body dynamic envelope.
• and by some further down the road concepts as e.g. by laterally displacing the coach body by 3 or 4 cm with respect to the running gear in order to avoid infrastructural obstacles or by tilting the coach body away from infrastructural obstacles. The implementation of such measures would require an advanced level of train control and seems unlikely in the foreseeable future.

Further, it is highly desirable to develop standardised advanced methods for vehicle gauging, based on simulations, thus making it possible to fully utilise the available structural gauge.

Comfort

More research and development is needed to better understand the relations between used space, experienced space, ergonomic factors and passenger’s positive / negative feelings, as well as their willingness-to-pay. It is also desirable to develop trains with even higher comfort in the long term. It is then favourable to increase interior width to at least 3.3 m. In such a case it is important to introduce new wall designs with reduced thickness (and maintained strength).

Capacity

Capacity considerations are the main motivation for using wide-body stock: Capacity expressed as number of seats per hour is essentially proportional to the number of seats per train metre. This means that wide-body stock increases capacity by around 20%.

Compared to normal trains:

• Capacity: Increased capacity of a line. Increased platform capacity.
• Night train comfort: The wide body is a prerequisite to design a comfortable night compartment with two beds along the side-wall.

Compared to double-decked trains:

• Equipment: In wide-bodies most of the equipment can be accommodated in the available underfloor space of the passenger car, typically 30 – 35 m³.
• Tilting: lower centre of gravity, possible car-body tilt and higher curving speeds,
• Catering: level floor within the train making it possible to arrange ambulant catering service
• Simplicity: simpler interior construction.

Infrastructure

The main obstacle for the introduction of wide-body stock lies in the infrastructure, which is not adapted to wide-body stock for historical reasons. For certain isolated networks (mainly suburban lines) and some regional and long distance lines wide-body stock could be introduced without major infrastructural changes. The demand for interoperability in intercity and high speed traffic limits the allowed stock width considerably. This can be exemplified by the ICE family: Whereas the ICE 1 and ICE 2 had a width slightly over 3000 mm, the ICE 3 facing greater requirements of interoperability has been constructed to 2900 mm only.

From the view of manufacturers a great obstacle is given by the paradigm of many operators to accept only stock that can in principle be used throughout the network. This impedes insular solutions for regional networks allowing wide-body stock.

Passenger acceptance of 2 3-arrangement

A 2 3 seating solution may result in a certain reduction of passenger comfort. Especially the middle seat of the 3-seat-arrangement may be considered uncomfortable and not be readily accepted by passengers. However this effect is over-estimated as various surveys in Sweden showed. The passengers were asked for their preferences expressed as willingness-to-pay for more comfort. Even the most negative result was only slightly negative corresponding to 2 % of ticket price for a 2 2- instead of a 2 3-arrangement.

Assessment of potential for insular solutions

An unbiased assessment of the operability of wide-body stock on parts of the infrastructure will mostly reveal major potential in local and regional operation. If a small number of obstacles has to be removed, a cost-benefit analysis has to evaluate the profitability of such a transition.

Critical revision of the paradigm of “regional interoperability”

Many railway operators only purchase stock with a high degree of applicability throughout their infrastructure. For example, DB AG wants a regional train used in Bavaria to be usable in other parts of the country as well. This obviously limits the potential for wide-body stock. A critical revision of this “regional interoperability” paradigm is needed to assess whether it is economically reasonable.

Only passenger trains.

High potential in isolated networks, such as suburban and some regional lines.

On main lines, potential may be much greater than commonly assumed:

In 1990 DB, DSB and NS concluded that stock of a max. width of 3200 mm at around 1600 mm above rail level and of normal width at platform and roof level could in principle be accomodated on these three systems.

A Swedish study concluded that it would be possible to accommodate a car-body width of 3.4 -3.5 m at “elbow height”, within the present structural gauges in Sweden and Norway, likely also in Denmark.

Studies by DB AG indicate that the main part of the ICE network with the exception of very few bottlenecks can be worked by trains 3.40 m wide. Concepts excluding narrow sections could be feasible in mid-term perspective on the major network axes.

Research by Swedish KTH showed that wide-body trains can be used on many markets, not only high-speed, InterRegio, local and regional trains but also for day-and-night trains. To make night-trains profitable in the future it is necessary to design trains that can be used both in night-service and in day-service.

Copenhagen urban trains

For the new S-trains needed for the Copenhagen suburban line, a Siemens / LHB consortium developed in close co-operation with DSB a train especially adapted to the local situation. The invitation to tender already contained a number of environmental requirements to be met by the manufacturer, among them a considerably reduced energy consumption.

In order to increase seats per train length and reduce energy consumption per seat, the car-body was extended to the outer limits allowed by track profile and station platforms. A car-body width of 3.60 m proved feasible (0.58 m more than the old stock). This allowed three seats on both sides of the aisle (old: 2 on one side, 3 on the other) and 336 seats per train set (old: 260 seats per train set) without changing train length. This along with a number of other measures (one-axle-bogies etc.) reduced weight per seat by 34 % to 357 kg. Compared to previously used stock, energy consumption was reduced by 60 % (!).

According to DSB, acceptance of the new trains is high both on the part of DSB personnel and of passengers.

Although a direct transferability of this particular train to other networks is doubtful, since the train was developed especially for the Copenhagen track profile and station platforms, the case can be seen as a positive example of how to implement a train solution in an isolated network that both optimally meets the requirements of the operator and energy efficiency.

In order to estimate the reduction of seat-specific energy consumption, conventional (2950 mm) and wide-body (3400 mm) versions of an otherwise identical train (e.g. equal length etc) are compared. These widths correspond to the conventional ICE 3 and to a wide-body ICE 3 based on a design study.

Aerodynamic effect of wider car body

The cross-section of the train is increased by ~15%. Since air resistance grows with cross-sectional area in a less than proportional way, it is safe to assume that air resistance grows in the order of 10% or less.

Mass effect of wider car body

The design study for a wide-body version ICE 3 yielded a mass increment of about 10% in comparison to conventional ICE 3 design.

Comfort functions

No data are available on the effect on the energy consumption of comfort functions in a wide-body train. For obvious reasons (less wall surface per seat, less interior space to be heated per seat etc), it is increased by less than the relative increase in seating capacity. 10% will be a safe upper limit here as well.

Energy consumption of the entire train

Since all components of energy consumption of a passenger train (mass, air drag and comfort energy) are increased by about 10% (or less), the energy consumption will also increase by 10% or less.

Seat-specific energy demand

Since seating capacity is increased by about 25%, the 110% energy consumption have to be divided by 1,25 to get the seat-specific energy demand relative to a conventional car design. The result is a reduction of seat-specific energy consumption by 12%.

Assuming that a maximum of half of the regional lines and some of the main lines could be operated with wide-body stock in long term, the applicability in most fleets will not exceed 25%, but could reach values of up to 40% in some fleets. Accordingly, this gives a maximum system-wide effect of 2 - 5 %.

According to a study by European Transport Consult, costs are squarely in favour of wide-body stock as opposed to double-decked stock.

The specific initial investment per seat is low compared to both normal and double-decked stock as can be seen by the following examples.

German DB has compared several train concepts for the ICE 4. Table 1 gives the relevant initial invest figures (Reemtsema, Kurz 1997).

Table 1: Initial investment figures for different versions of ICE 4

Source: Reemtsema, Kurz 1997

A Swedish study (Andersson et al. 2001) on wide-body stock yielded the initial investment figures shown in the following table.

Table 2: Initial investment figures for wide-body trains

Taking the average values from both studies, we get:

• Train fix costs typically increase by around 10% compared to normal trains.
• Specific fix costs per seat are reduced by around 10% compared to normal trains.

Maintenance costs: an increase of 4% for entire train and a decrease of 14% per seat according to a Swedish study.

Energy costs: per seat: 10-15% reduction

Highly dependant on required infrastructure changes.

Life-cycle costs (LCC) can be cut by up to 12 % per seat.

German DB AG estimates that the cost savings due to the operation of wide-body trains on the ICE network are so high that, even if the full costs of removing bottlenecks are charged to the programme, there will be cost savings in the mid term of 50 - 70 million Euro per year.