Facilitating traffic growth in the Netherlands: the ‘Triple A’ strategy approach

Over recent years, minds have been focused on improving the system reliability of the Dutch railways. So far, it has proved possible to shoehorn the capacity requested by transport operators into the timetable each year, even though the network is one of the most intensively used in Europe. Now that reliability has been put in order, and the demand for capacity is increasing, the time is right for expansion and for raising capacity utilisation above traditional standards.

ProRail is developing a new strategy for achieving a 50% increase in the rail network’s capacity, which revolves around smarter planning, building (where appropriate), and reorganising the train service where possible. The plans, for as soon as 2012, are to operate several of the busiest corridors without a fixed timetable for travellers, in what is known as the ‘metro’ or ‘travel without a timetable’ concept. The idea is for a train to run every ten minutes for everyone, whether for local or long-distance travel, and to introduce a ‘green wave’ system for freight transport. Passengers will be less focused on punctual departure if they never have to wait a long time for the next train.

The state of Dutch rail tracks

Expansion on the railways in recent years has been relatively vigorous, at between 2.5% and 5% annually for passenger transport, and between 3% and 10% for freight. Among the contributory factors to the growth have been road congestion and rising fuel prices. The government has revised its target for rail-based public transport expansion upwards to 5% annually. An increase in passenger traffic is foreseen of up to 50% by the year 2020. This amounts to between 18 and 23 billion passenger-kilometres, compared with 15.5 billion in 2007. The freight volume is set to double, from 42 million tonnes to between  80 and 90 million tonnes.

However, the growth trend around the country and at different times is extremely varied. It will still be possible on many routes to absorb the expansion with existing trains, whereas longer or higher trains can be used elsewhere. However, this approach is a continuation of the current approach to capacity, and, in many routes in the densely populated western part of the Netherlands, lead to overload after 2012, without changing current procedures and practices.

ProRail’s Triple A strategy was devised to facilitate the higher frequencies of the ‘travel without a timetable’ concept. The greatest benefit of this strategy for freight transport will be fewer unnecessary stops in the routes, through the use of a ‘green wave’ approach.

The Triple A strategy

A rail line has a theoretical capacity of thirty trains an hour. In practice, however, no more than twelve trains run every hour on the busiest rail lines at the busiest times of the day. This means that less than 40% of the theoretical capacity is now being utilised. If we abandon the customary way of thinking and acting, we could return to the assumption of thirty trains an hour in the quest for what is possible. Better capacity utilisation means introducing three different approaches (in Dutch the word ‘anders’ is used for the English ‘different’, hence Triple A).

A different approach to capacity planning and timetabling

Analyses of actual timetable performance that have been conducted in the past two years have exposed margins in the current planning and execution of the train service. Revising and introducing differentiation into the planning standards, adopting a different approach to planning, and introducing a process of continuous operational improvements (‘removing slack’), will raise the quality of the train service while creating scope for further expansion on the existing network.

Capacity growth restrictions in the current approach are attributable mainly to the planning rules: a capacity bottleneck arises if the requested specifications cannot be achieved on the basis of common standards and assumptions. This approach implies on paper that there are many bottlenecks in the Dutch rail network. In the new approach, we identify bottlenecks by investigating points in the execution where major and systematic obstacles affect multiple trains. The following measures, which come from practical experience and analyses, will be applied in eliminating the bottlenecks.

Use margins specifically

For example in calculating journey times, intervals between trains, halt durations and turning times. Because the existing margins are often ‘stacked’ in the timetable, they often occur at non-optimum locations and times.

Resolve conflicts as they occur  in execution

Practical experience has shown that the current conflict-free timetabling is not always optimum. Conflicts still arise when trains are delayed and do not run to timetable. Often it would appear to be better and more efficient to resolve conflicts as they arise. New opportunities are created by abandoning the objective of completely conflict-free timetabling. A case in point is the conflict in Amsterdam Central between the path of the Thalys from Paris  and a freight path to Westhaven. The Thalys runs six times a day and the freight train three times. The probability of these trains being scheduled at the same time is therefore low. The probability of them both also running exactly on time is even lower. If the conflict is solved when it occurs, rather than in a 100% conflict-free timetable, a lot of potential capacity has been won.

Optimise interventions

Interventions during operations now often put an additional load on the capacity of the bottlenecks; not only because of the additional (crossing) movements, but also in terms of staff and rolling stock planning. Gains can be made in these areas too, by avoiding the additional load on the most critical capacity caused by intervention activities. For example, it was decided in 2007 to arrange for all remaining crossing movements at Schiphol to occur outside the tunnel, where they can be performed more rapidly, and where there  is no stationing process that might influence  the train process.

Avoid crossing movements

Trains with crossing paths use twice as much capacity as trains that run independently of each other. The train service, in particular at hubs, can be organised so as to reduce the number of crossing movements. This can often be achieved without timetable changes, and without forfeiting the most important ‘cross platform’ connections. This approach was successfully implemented in June 2007 for the Utrecht intersection. Reducing the number of crossing movements throughout the network will make the network as a whole less complex, and therefore more resilient.

Disentangle hubs

An extreme form of reducing crossing movements is the design of segregated corridors. The 80/20 rule (which says that 80% of the effect is achieved with 20% of the effort) suggests disentangling the major hubs, which would involve changes that are relatively small to the current train system. This exercise would create sub-networks rather than separate corridors. In turn, it would create opportunities for better balancing the distribution of trains, and therefore also the passenger flows at stations (on escalators, lifts, etc.).

Reduce unutilised capacity claims

Since part of the capacity in the basic hourly pattern (i.e. the regular timetable pattern that repeats throughout the day) is not used every hour (e.g. rush hour routes, international routes and freight routes), slack is introduced into the timetable. An example is the scheduled opening of movable bridges, of which there is a significant number in the Netherlands.

A different approach to  capacity allocation

Rail network users have many and varied needs, which taken together, determine the capacity demand on the network. There is much to be gained from taking a critical look at the impacts on capacity of this package of needs.

The specification of the capacity needs

It is vital in formulating the capacity needs to have an explicit statement of all wishes and assumptions, which must be specified in terms of time, place and other quality aspects. A specification in terms of time means that transport operators request different patterns for different periods of the day. The same applies to maintenance. It is conceivable that not all freight transport is bound strictly to time, but has leeway in this respect. The starting point, therefore, is not the hourly pattern, but the actual capacity need.

Identifying and utilising solution space

Solution space may be sought in differentiating by time, differentiating by place, easing the progress of trains through the bottlenecks, streamlining frequencies, and differentiating the environmental burden. The use of passenger trains is concentrated strongly in the rush hours. It might be worthwhile exploring the possibility of offering lower frequencies outside the rush hour, in order to create more space for freight trains in these periods. Already, most maintenance on busy routes has to be carried out at night. The most efficient capacity enhancement solution is to plan for smooth circulation at the places that determine capacity: the bottlenecks. Most of the bottlenecks are in urban areas, where track expansion would be difficult and expensive. Streamlining can be achieved by delaying intercity trains, speeding up urban and regional commuter trains by using rolling stock that are able to accelerate quickly (‘light trains’), and easing the progress of freight trains through cities by introducing a ‘green wave’ system. This approach would typically demand adjustments to the infrastructure, especially at junctions. Finally, plans are being made for using the new Betuweroute as a turntable, or artery, for the majority of freight. Some busy corridors would then become dedicated passenger routes.

Employing the price mechanism

Although at this moment the instrument is not being utilised, differentiated access charging may become a useful instrument in striking the right balance between commercial and public interests in the near future, by diverting and spreading traffic in time and place.

A different approach to capacity growth planning

Finally, we must look even harder than we already do for the most cost-effective measures. This also implies that the actual utilisation and costs of assets is continuously monitored. A good example is the approach taken in Switzerland, where no new infrastructure is considered without an agreed timetable. Cost-effective measures mean starting with specific investments in small-scale solutions that can be implemented inexpensively and quickly. Solutions do not necessarily reside in large-scale expansions  and technical system step changes, that have often been considered in the past as the way forward (fully four-track sections between the larger stations, 25kV overhead electrification, and so on).
As an example, overtaking tracks can allow fast trains to pass slow trains with little loss of time. In combination with streamlining the trains and reliability of operation, a differentiated 6/6 system would then be within reach for the construction (or improvement) price of an overtaking facility. The disadvantages compared with fully four-track sections are:

• Several minutes additional running time for an intercity because of the streamlining, which could be utilised for additional stops in urban areas
• Several minutes additional time for  urban commuter trains because of the overtaking facility

The current rail network already has overtaking facilities in the form of a few four-track sections, hubs with many tracks, and local overtaking arrangements. It would be a good idea to utilise these facilities more effectively and to improve their layout, improve signal positioning, and tighter scheduling of trains relative to each other. ProRail ran a pilot in 2008 for the introduction of ‘rapid overtaking’, which would limit to two minutes the time lost by an urban commuter train.
Running more trains also means having somewhere for them to stand while being maintained or when not in use. Looking at examples from other countries, we see that small-scale solutions in outlying areas are usually more cost-effective than large-scale areas in the cities. For example, consider the commuter rail networks in Spain (Cerçanias), where the units are kept and maintained in small-scale ‘garages’ at the termini. It may even be appropriate in some cases to sell existing junctions in urban areas in exchange for small-scale solutions outside the area.

The follow up of this strategy

ProRail wishes, with its partners in the rail industry, to embark on a different path in order to achieve the ambition of growth in the busiest parts of the network as early as 2012. This will raise the utilisation of existing infrastructure above traditional standards. Experience from Japan and countries elsewhere in Europe suggests that solutions for capacity bottlenecks can often be executed on a smaller scale and with more specific aims, thereby also substantially shortening the implementation periods involved.

At the end of 2008, the Ministry of Transport earmarked €4.5 billion over the next few years for investment in introducing the Triple A strategy in several corridors, in order to resolve capacity bottlenecks. Making Triple A materialise will be a substantial challenge for all parties, in particular because of the changes it demands to established customs. There is no single solution that will always work everywhere. All three ‘A’s will have to be used, with no fixed sequence or priorities. Indeed, it will be a matter of tailored combinations at each location. Furthermore, there will be no rigid choice between utilisation and building. We will look instead at the most cost-effective mix of measures. For instance, relocating or adding signals and constructing several overtaking tracks may be more cost effective than conversion to four-track operation.

Traffic measures could provide a pro-active way of resolving implementation conflicts, but this also requires additional skills and tools in the traffic control centres, in combination with those of the transport operators’ staff on the trains. Examples are the addition of new points at crucial locations, additional workplaces and supporting information and decision systems for traffic controllers, passengers and drivers (the Routelint tool) and systems for flexible, ‘dynamic’ platform use, as introduced at Schiphol Airport. As they are now, the hubs are often significant bottlenecks.

At the same time, the requirements (on quality and reliability) placed on infrastructure elements, rolling stock and personnel will be raised even higher in order to prevent system instability. It is important that European technological developments favour this intensive capacity enhancement, for example through the release of ERTMS and through facilitating TSI regulations, such as those for the braking performance of rolling stock.

Finally, we believe that the Triple A strategy not only contributes to cost-effective and quicker, stepwise solutions than traditional building concepts, it also contributes to improved sustainability. Existing infrastructure is first to be utilised beyond today’s capacity limits, before any new investments in concrete, steel and ballast are considered.