Various European railways have tested driving advice systems.

• At Dutch NS prototypes have been developed by NedTrain Consulting in 1996 and were tested in regular passenger service for two years.
• German DB runs a pilot on the ICE 1 and 2 using a DAS developed in co-operation with Hannover University.

Systemic optimisation

Future driving advice systems could integrate a link to the control centre and thus take into consideration unscheduled stops arising from the traffic situation. This would require some communication channel between the DAS and the control centre as well as a corresponding IT support at the control centre.

Extended functionalities

Future driving advice systems could go far beyond giving driving recommendations and offer a wide range of functionalities such as monitoring for maintenance processes and accident investigation etc.

Punctuality

In-service testing in different systems have shown clear improvements in punctuality.

Capacity

DAS could help drivers to stay inside their infrastructure slot at all times. This would improve slot management and thus increase capacity.

Wear

Coasting instead of braking reduces the wear of the brakes especially if electric braking is not possible.

Passenger comfort

Small improvements in passenger comfort can be achieved through smoother driving. In addition, early train arrival often leading to trains waiting outside stations (a situation hardly comprehensible for passengers) is ruled out by DAS.

Availability of digital infrastructure data

For a system-wide introduction of DAS-based energy efficient driving, infrastructure data have to be supplied in a digital form, containing the exact position of stops, junctions, curves and curve radii, slopes etc. In most railway companies these data are only available on paper. Digital version may be obtained by different methods:

• Manual data conversion: This method is very liable to mistake and proved insufficient at DB AG (for the ESF project, cf. Example)
• Laser scanning of infrastructure: A special vehicle with a mounted laser scanner “scans” the whole infrastructure. This method is very expensive (~ 2 million EURO for a country like Germany, France or Spain)
• GPS scanning of infrastructure: This method is cheaper and was applied in Austria. However the result is less accurate compared to laser scanning.

The digitalisation of infrastructure data is one of the principal bottlenecks for the implementation of DAS systems in countries with a big railway network. In smaller railways like SBB, a manual route-by-route approach is feasible.

Updating of track information

For the effectiveness and reliability of DAS recommendations, up-to-date information on track conditions are crucial. If static track and timetable information is used, temporary low-speed sections are not taken into consideration and may lead to DAS causing additional delays. Dynamic information could be supplied via an automatic update at stations (e.g. by a W-LAN link) or via continuous updating by GSM (or other). At DB AG it is planned to make use of the new electronic timetable method (EBuLa) as a data basis for the driving advice system ESF (cf. Example).

Acceptance by drivers and management

Some drivers will be reluctant to follow the recommendations of a DAS for several reasons:

• If drivers experience train delays caused by insufficient or wrong infrastructure information in the DAS (e.g. temporary low-speed sections), they will no longer follow the system’s recommendations.
• Some drivers may experience DAS as a step towards automatic train control and therefore as a step towards losing their jobs.
• If drivers are not intensively familiarised with the DAS, many will not understand the system and will take the recommendations as irrelevant additional information.

Some decision makers think that acceptance by drivers puts too much uncertainty to the effectiveness and thus payback of the system.

Delayed trains

The effectiveness of the system is reduced if train punctuality in the network is low, since the DAS has no effect in this case.

Unexpected stops

If unexpected stops due to red signals occur on the trip, the DAS can no longer operate or may even lead to additional delays. This cannot be avoided even by up-to-date track data, but would require a permanent link to the control centre being a future upgrade of DAS.

Computing power

DAS being a real-time-application, limitations of computing power installed on-board may pose a problem in some cases.

Time buffers

A pre-condition for the use of DAS is the existence of time buffers in the timetable. The saving effect of DAS is the higher, the bigger these time buffers are.

Winning drivers’ acceptance

• Special training programmes have to be given to drivers
• Communication of the new system should focus on the purely advisory character of the system and stress that the system supports drivers to fulfil their core task being punctuality.
• Human-machine interface has to be optimised and the information has to be presented in a clear and functional manner.

Integration into existing ICT infrastructure

When developing or introducing a DAS, synergy effects with existing hardware platforms as well as positioning and data supply systems should be sought in order to reduce costs and overall system complexity.

International standard

An international standard for DAS could create scale effects for the development and introduction of such systems. Furthermore, synergy effects with other international systems such as ETCS can be ensured at an early stage. A UIC project aiming at the definition of standard requirements for energy meters and DAS was finalised in 2002.

German driving advice system ESF

In co-operation with Hannover University, German DB AG developed a driving advice system called ESF (Energiesparende Fahrweise). The system gives coasting advices based on track and train data, timetable, position and time. Continuous speed optimisation could also be given by ESF but is presently not activated. The savings to be realised strongly depend on timetable, operational situation and degree of energy efficient driving previously realised by drivers’ skill. An average saving potential of over 5 % on German ICE has been confirmed by tests and calculations. A pilot on ICE 1 and 2 was realised in 2001. At the end of 2002 ESF is planned to start in all ICEs running on lines where the new electronic timetable method EbuLA has been successfully implemented. Exact structure data of the entire network is needed in a reliable and convenient digital version in order to successfully run both EbuLa and ESF. This is the main reason for these systems being restricted to only part of the network in the initial phase.

Comparing a DAS guided driving strategy with a shortest time driving strategy one gets the theoretical saving potential. For typical time buffers and running patterns, it lies over 20 % in main line operation.

The real saving potential is however considerably lower, for three reasons:

• Even without DAS drivers do not pursue a shortest time driving strategy, but use a more energy efficient driving style according to their experience, skill and motivation. If there are no delays this may cut energy consumption by 20%.
• Due to delays the DAS often cannot be used. This may well be the case for about 50% of the trips.
• Purely advisory character of the system: Some drivers may ignore the advice.

Taking these factors into account, the remaining potential in main line transport lies between 5 and 10%. In individual favourable situations this value can even reach 15%.

ESF test runs at DB AG

Simulations and test runs with ESF on the ICE at DB AG yielded the following results:

• The theoretical saving potential is 21,2 %.
• Taking into account that drivers exploit some of this potential without a DAS, the remaining potential is 14,9%.
• If train delays are also taken into consideration, the average savings are about 7,5 %.

Economymeter test runs at NS Reizigers

In-service testing during two years in the Netherlands has yielded an overall reduction of 6 – 7 %. The reason for this value which is much lower than the theoretical potential are delayed trains and drivers ignoring the driving recommendations.