Turning Japanese

It appears that the Rt Hon Simon Burns MP, Transport Minister, took the opportunity of the February 2013 Westminster recess to visit Japan. A newspaper article says that he was looking at the “famous ‘bullet trains’” that operate in that country. I’m sure that his Japanese hosts will have been keen to impress; after all some big money will be spent on the purchase of high speed trains for HS2, and Japan will want to build on its success with providing the Class 395 “Javelin” trains for the HS1 domestic service.

Whilst the newspaper article is more concerned with Mr Burns’ view of the possible impact of the “legal challenge” on the timetable for HS2 – the judgement had not been delivered at the time that the article was written – there is one, and only one, sentence in the article that relates to the presence of the minister in Japan:

“Mr Burns said there were lessons to be learnt from the Japanese experience, for example techniques to mitigate noise pollution.”

I wouldn’t disagree with the minister on that; the Japanese are arguably the world’s leaders in techniques to reduce the noise emitted from trains at the source. But, what the newspaper article doesn’t tell us is whether the minister has given any thought to why this might be. Surely the motivation that has led the Japanese to this position is the real lesson to be learnt.

The simple truth is that the Japanese have put so much effort into research and design to make high speed trains (Shinkansen) quieter because the Japanese Government has, since 1975, imposed legal limits on the noise pollution that they are allowed to cause. In my blog That’s much louder than the average (posted 29 Nov 2011) I referred to this legislation, but there I was more concerned with the units in which the limits were expressed, rather than the impact of the legislation. It is this latter aspect that I will look at now.

The Japanese legislation sets a maximum limit on noise within a residential area, between the hours of 06:00 and 24:00, of 70 dB L_pASmax. This limit applies to all new lines and time limits are also set by which existing lines should be brought up to this standard. In the units chosen for HS2 this is equivalent to 56 dB L_Aeq,18hr. This starkly illustrates how far the United Kingdom is behind Japan in this matter; the Japanese limit is a full 9 dB below the noise level which qualifies for a sound insulation grant in the UK (taking 65 dB(A) as the free-field equivalent of the 68 dB(A) façade measurement specified in the The Noise Insulation (Railways and Other Guided Transport Systems) Regulations 1996).

Faced by the stringent noise pollution limits applied, the approach taken by the Shinkansen’s designers has been two-pronged: to reduce the noise-generating potential of the train at source (e.g. see this paper), and to protect receptors by widely employing noise absorptive barriers (e.g. see this paper). The Japanese also make far more extensive use of tunnels than HS2 Ltd is proposing.

The only emission limit that seems to apply to the design of HS2 is set by the European Union in its technical specification for interoperability (TSI) relating to the ‘rolling stock’ sub-system of the trans-European high-speed rail system, which has been adopted as Commission Decision 2008/232/CE. Paragraph 4.2.6.5.4 on p. L 84/198 of that document stipulates a maximum train pass-by noise level of 92 dB L_pAeq,Tp ±1 dB, measured at 25 metres when the train is travelling at 320kph. Since this specification did not envisage that any European trains would run above this speed, it has been necessary for HS2 Ltd to “adjust” this limit to 95 dB to take account of the 360kph running assumed for the noise calculations.

The protection offered by the TSI does not look very impressive when compared with the Japanese legislation. Using a simple 6 dB reduction for each doubling of distance from the track, you would have to move 400 metres from the track before the attenuation due to distance reduced the noise to the Japanese limit. This means that anyone living less than 400 metres from the track will depend upon additional mitigation, which HS2 Ltd will not be bound to provide, or be blessed with topographic mitigation (such as a cutting) to fare as well as a Japanese resident.

So far HS2 Ltd has refused to be drawn on whether it will set noise limits to determine the noise mitigation that will be offered, or if noise mitigation measures will be determined more by economic considerations. I suggest that HS2 Ltd would do well to follow the example of Chiltern Railways, who have published a Noise and Vibration Mitigation Policy document for the Bicester to Oxford Improvements project. Whilst the provisions of this document are not as binding as one might wish, they do at least represent a step in the right direction of giving those living and working near the line some assurance that any noise issues will be addressed.

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