Monday 1 August 2011

Road noise and the Dutch cyclist

This video had explanatory captions visible on screen but youtube removed that facility. While traffic noise exceeds 90 dBa from right next to the road inside the noise barrier, ambient noise from the motorway is 50-55 dBa on the cycle-path at the closest point to the motorway, which is quieter than children playing further away and also quieter than slow cars on the access road. It's unmeasurable by the time I am a hundred metres from the motorway.

Noise pollution contributes towards a great number of different health problems. Noise from roads is a very common source of noise pollution. In some places it dominates the outdoor landscape. However, this does not have to be the case.

Motorways in the Netherlands are quite remarkably quiet compared with those in other countries. It is often possible to stand just a few hundred metres away without being aware that you are near a major road.

This has been achieved by use of special quiet road surfaces and noise barriers. Also, speed limits can be lower on motorways where they are near residential areas. This reduces both noise and air pollution from motor vehicles close to where people live.

In the video I measure the noise levels on and near a motorway. Right at the side of the road, figures of 90 dB(A) and above were quite common. However on the other side of the noise barrier, just 20 m away, figures of 50-55 dB(A) are normal. That's within the range of normal conversation and quieter than the noise made by a child in the park a much greater distance away. A little further away again, about 100 m from the road, it is much quieter and my meter can no longer measure anything at all.

How does this relate to cycling ? Riding a bike on a noisy road, whether or not it includes on-road cycle lanes, is always going to be a relatively unpleasant experience. The noise of motor vehicles close by will always reduce the subjective safety of cyclists. Cycling thrives where cyclists are kept apart from all effects of motor vehicles, including their noise.

Update later in the day
This is the location where I made the video:

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This is another road, the ring road of Assen, which has a 70 km/h speed limit and noise barriers:

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This road has a 50 km/h speed limit and noise barriers against the side of the road which is residential:

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Such barriers are not at all unusual. There are others around the city.

You may also be interested in the works of the Noise Innovation Programme, who have produced reports on such things as "State of the Art Acoustic optimisation" of roads. They also concern themselves with noise from trains and marshalling yards. I once worked in an office situated close to a very noisy marshalling yard in the UK, so it was interesting to read that piercing curve noise actually can be reduced, though we were assured at the time that it could not.

There are several other blog posts about noise, covering different aspects, and giving other examples of treatments as well as links to more information. Also there are blog posts showing Stiltegebieden or "Silent Areas" near Assen. These are places just a short distance away where you usually can hear nothing but birds and insects, and the sound of other cyclists passing. It wouldn't be possible if road noise had not been tamed.

Source of the noise
Note that the noise from cars shown in this video is almost entirely due to tyres wearing on the road. It's not produced from the exhaust pipes of cars. This is why quiet asphalt is effective. It's also why electric cars are not a solution to the noise from cars. Engine noise was already insignificant for any moving car. Reducing it does not reduce total noise pollution from moving cars, and stationary cars make no noise anyway.

Comparisons of typical noise levels of different things are here. I don't get to use my decibel meter often. The last time it came out of the cupboard was to test bells.