The sound of a Shinkansen train

This is a guest post by Peter Delow, written specially for the Stop HS2 blog. Peter normally blogs at the HS2 and the environment.

Officially known as Shinkansen, which means “new trunk line”, these Japanese services have been available for nearly fifty years. The first line, linking Tokyo and Osaka, came into service in 1964 and the network has gradually expanded to link most major cities on the islands of Honshu and Kyushu, with a total line length of nearly 2,500 km.

From a modest speed limit of 210 kph in 1964 the maximum operating speeds of the Shinkansen has gradually been improved to up to 300 kph in parts and this will shortly be increased to 320 kph on a few sections. Prior to 1964 it took nearly seven hours to travel between Tokyo and Osaka by train; today the journey time, by the fastest train, is down to 155 minutes.

Japan is a relatively small country with a large population for its land mass. The centre is very mountainous and, as a result, the population is concentrated in the coastal plains, adding to the population density. Only 20% of Japan’s land mass is habitable. This means that human habitation is never far from the Shinkansen’s tracks. Between Tokyo and Osaka, 56% of the track is through residential areas and a further 30% through commercial areas. This only 14% of the 513 km of track is through relatively undeveloped countryside.

From the very start the proximity of people’s homes to the Shinkansen’s tracks has meant that noise has been a controversial issue. When the Tokyo-Osaka link first opened the peak noise suffered in some locations was as high as 90 dB LpASmax; this is about the same level as a diesel truck at a distance of 10 metres. Strong reactions from those affected led to the Ministry of the Environment of the Government of Japan intervening and issuing “environmental quality standards” that require peak train pass-by noise levels to be reduced over time to a maximum of 75 dB LpASmax in commercial areas and 70 dB LpASmax in residential areas.

The system operators have responded by implementing a programme of noise reduction measures that includes improved track design and maintenance, reducing the weight of rolling stock, reducing the number of pantographs per train and improving their aerodynamic design and maximising the efficiency of trackside barriers and increasing their deployment.

Despite these noise reduction measures having had considerable success, there is a view in Japan that noise emission considerations may mean that high-speed rail operating speeds have, at 320 kph, just about reached the feasible limit. This is because the noise energy at speeds over 300 kph increases proportionally to the sixth to eighth power of the speed; so, for example, a 6 % increase in speed leads to a 140 % increase in noise.

If our Government insists on implementing HS2 it can, and must, learn lessons from Japan. First and foremost it must take noise pollution seriously, rather than the shabby attempt to downplay its effects that we have seen up to now.

Secondly, rather than HS2 Ltd setting its own noise limits, as appears to be the case now, these should be prescribed by an appropriate external body; Defra seems as obvious choice if we are to follow the Japanese model. Any noise limits specified should be based upon the peak noise of a single train pass-by; there are genuine concerns that the useof the equivalent continuous noise level LAeq,18hr, relied upon in the HS2 Appraisal of Sustainability (AoS), understates the noise affects of high speed trains.

Any noise limits prescribed should be in line with the Japanese model. Levels entertained in the AoS are well above what the Japanese consider tolerable. For example, 70 dB LpASmax (the Japanese limit for residential areas) equates for HS2 to around 56 dB LAeq,18hr, which is in the middle of the “grey dot” classification used in the AoS. In contrast, the “red dot” classification starts at 73 dB LAeq,18hr, which is 17 dB above the Japanese limit (nearly four times as loud to our ears).

Thirdly, HS2 Ltd must develop a credible and detailed noise mitigation policy as a matter of urgency. It is simply not acceptable to pretend that the 3 metre noise barriers currently specified will be adequate or that it will be possible “to control aerodynamic noise through advanced rolling stock design” to produce the appreciable reduction in noise levels of around 20 dB that were assumed for the soundbooth demonstrations at the roadshows. We also need an urgent review into whether operating speeds of 360 kph, rising to 400 kph in future, are feasible in the light of the view in Japan that 320 kph may  represent the practical limit.

It appears to me that, when it comes to protection from high speed train noise, the Japanese public is being treated with far more respect and consideration by its government than ours has shown its citizens up to now.

Acknowledgements: In preparing this blog I have relied heavily on the data in the following articles

H. Okada, “Features and economic and social effects of the Shinkansen”, Japan Railway and Transport Review 3 (1994), pp. 9–16.

Smith, Roderick A. (2003). “The Japanese Shinkansen”, The Journal of Transport History (Imperial College, London) 24/2: 222–236.

PS Don’t forget to check out Peter’s blog at HS2 and the environment.