Since May 2021, Metroselskabet and supplier Hitachi Rail have stepped up the maintenance of the metro train wheels as it has proven to have a beneficial effect on vibration levels, which have now been reduced to a stable, low level. It is vibration that creates sound, which to some neighbours is perceived as noise. This can be seen both in the vibration measurements that are taken regularly and in the number of complaints from neighbours, which has decreased. The Metroselskabet has therefore decided that the supplier must carry out maintenance of the metro train wheels more often in the future. At the same time, there is a continued focus on taking the trains that create the most vibrations out of service.

‘We transport more than 300,000 passengers in the Metro on a normal weekday, and more than 100,000 passengers use the M3 line daily. It's an important transport task that we fulfil for the city's citizens and its guests. At the same time, we must also take good care of our neighbours, which is why we have made it a priority to increase the maintenance of the wheels on the trains running on the M3 line, as we can see that increased wheel maintenance has a significant positive effect - not least on the number of neighbour complaints. In addition, we have an ongoing focus on taking out for maintenance the trains that create the most vibrations and thus noise for the neighbours,’ says Hanne Tærsbøl Schmidt, Head of Neighbours and Properties at Metroselskabet.

Over the summer, experts from consultancy firm Ramboll and supplier Hitachi Rail conducted a series of tests to assess the possibilities of further reducing the nuisance experienced by some neighbours. The tests examined the possible positive effects of adjusting the rail inclination and track gauge as well as lubricating the rails. The studies have now been completed, and the analyses have shown that rail lubrication should be further investigated as it may have a beneficial effect on the level of vibration in some places on the M3 line. The other measures showed no effect, so there is no basis for further work on them.

‘Our supplier, in collaboration with external experts, has conducted a number of thorough tests and analyses over the summer. Based on this, we have assessed that treating the rails with a special lubricant in some places on the line can have a positive effect on vibration levels. We are now investigating this further together with our supplier. The other measures tested did not provide sufficient basis for further testing - and thus we can conclude that adjusting the track width or track inclination will have no effect on the noise level in the apartments,’ says Hanne Tærsbøl Schmidt.

Despite increased wheel maintenance and the removal of trains, data shows that there are still places on the M3 where neighbours feel disturbed by train operations. Metroselskabet is therefore continuing to work with consultants and the supplier to localise the causes in the hope of finding solutions. This includes installing more measuring equipment. Even though work is continuing to reduce vibration levels, it is likely that there will still be neighbours who experience that some trains on the M3 are audible in the future. Out of approximately 15,000 households on top of the M3 line, around 450 have experienced nuisance from metro operations since it opened in 2019.