Modernising Prague’s tram infrastructure
Posted: 31 August 2017 | Miroslav Penc (Head of Tram Infrastructure Unit at Prague Public Transit Company) | No comments yet
With over 340km of track, modernising Prague’s tram infrastructure is a big job. Here, Miroslav Penc, Head of Tram Infrastructure Unit from the Prague Public Transit Company, outlines some of the work being done to improve Prague’s tram tracks and upgrade the network’s signalling system, all without inconveniencing passengers or adding to the programme’s budget…
Prague’s tram (or light rail) network has been in operation since 1875, and throughout that time has gradually expanded into its current 142km double track network. With tracks in depots included, its length is 340km of single track in total and it has 940 switches. Owing to last year’s economic growth, the number of trams in operation during the morning peak exceeds 400, which is the highest number in the European Union.
All of this use results in track deterioration. Key factors in the deterioration of tracks include its construction method, its age (including superstructure), the weight and power of the vehicles on the track, and the level of tram and other vehicle traffic.
Over the past 10 years it has been necessary to improve the condition of Prague’s track as it was in rather bad condition due, in part, to the delivery of many low floor vehicles. These vehicles have been equipped with more power to provide good acceleration on gradients over 7% and they weigh more due to the technology involved in low floor vehicles.
As part of Prague’s track infrastructure renovation programme, the BKV system (also known as the Nikex system) – which is track construction using block rails with concrete plates – has been replaced by the construction method of using standard sleeper tracks (both with grooved and vignole rails) and slab track. A sleeper track is generally used on separated right-of-way open or grassed track, while slab track is mainly used as an on-street track form covered with asphalt layers.
The construction of slab track is designed to contain a minimum number of steel parts – often only clamps, screws and screw pads – to allow the use of milling machines when the structure is at the end of its life. Standard sleeper tracks with vignole rail (profile 49E1) also bring a significant reduction of noise and vibration emissions.
The Prague Public Transit Company (DPP) carefully researches the interface between rail and vehicle before a massive investment in tracks begins. Finance for such a large investment programme comes from European funds, depreciation, and subsidies from the city budget. In the present budgetary period, however, there are no more EU funds for reconstructions.
Figure 1 illustrates the pace of track renovation for 2009-2016, with the all-time record of reconstructed tracks in the system taking place in 2013. The result of this huge undertaking means that 41% of the tram tracks have been modernised in just eight years. This modernisation process covers depot tracks as well, with most never having been modernised in their history. Depots are adapted to accommodate vehicles with a higher axle load, as well as having new or improved access to the roof. Depot tracks are also newly put on standardised prefabricated reinforced concrete structures instead of steel structures.
Hand-in-hand with track modernisation comes the rebuilding of platforms, or building new barrier-free access to vehicles. It is a city requirement that all stops have barrier-free access by 2025 and currently, the tram system provides such access at 76% of stops. The rebuilt platforms are often wider, have more space for passengers and provide better protection. Barrier-free access means not only step-free access for wheelchair users or prams, but also a system of navigation for blind and visually-impaired people. Maximum platform height is now 24cm, and with the phasing out of vehicles with swing doors, it will be possible to raise this to provide access to most vehicles, as has been made common by the new French tram systems.
The next stage is to replace the 65km of track outside depots, as well as to replace three depots. However, this work is restricted by the overall modernisation of street space, so the current projects are more complicated and comprise many interactions with other players and their projects. Our goal is still to lower the interruption of services as much as possible and to improve geometry to get better ride comfort.
The main maintenance issues have to take into account the frequent services during the day (there are typically just 1-4 minutes between trams in each direction) as well as a full overnight service on almost all networks. With a very high proportion of new rails already in place, the need to replace them is not urgent, but we must be prepared as the rails get older.
Modernisation of infrastructure must also take into account future network expansion plans, i.e. locations where there will be a junction in the future, so there are provisions for cheaper and easier installation (right axial distance of tracks, water drainage for future switches, right horizontal position of tracks for future crossing through adjacent road lane and so on) of future tracks. DPP also makes an effort to monitor all other utility projects in the area so new or relocated utilities are not to be installed into the space that is intended for a future tram line.
Utility owners or caretakers (logically) often wait for track modernisation or installation to take place to lower their own expenses. We believe that a careful approach and preparation should reduce overall public expenses, and it is especially important that the expansion of a public transport network finishes on time. This should all be planned on an urban planning level, as unfair costs simply add to a light rail project budget (which is then criticised for being too expensive). But light rail brings more benefits to a public space than tracks or a comfort transport connection alone (this is the same issue for bus-dedicated infrastructures).
When it comes to the electrical equipment, there are 340km of overhead catenary, 41 substations to feed the electricity, and between it and the tracks, there are hundreds of kilometres of cables. The pace of the modernisation of electrical assets has been continuous in the past few years and the intention is to continue in the same way. The DPP is also planning to transition the control system from contact operation with manual inputs from the driver to radio transmitted signals controlled automatically from the on-board PC. All switches should be automatically controlled from 2021 onwards.
All of the effort being made thus far is to push Prague’s tram infrastructure to be modern, financially effective, durable and provide comfort for passengers.
Originally a civil engineer and later a PhD graduate of Faculty of Transportation Sciences, Miroslav Penc is now Head of the Tram Infrastructure Unit at the Prague Public Transit Company. With almost 20 years’ experience he is currently responsible for all tram and light rail infrastructure in Prague. The Tram Infrastructure Unit provides maintenance and repairs of main assets as well as participating in the reconstruction programme.