Monday, 1 August 2011

Road noise and the Dutch cyclist

This video has explanatory captions which are only visible if it is played on a computer. If you play the video on a mobile device then you will not understand the point that it makes.

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:

View Larger Map

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

View Larger Map

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

View Larger Map

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.


John in NH said...

Wow is all I have to say... Just wow. The major highway near me, 4 lanes 55mph is louder for me and I am ~1 mile away from it! Let alone traveling under it which I have to do daily. That is really quite impressive. It is a shame we can not copy such investment, but when we cant even find money to pave the roads let alone research and develop noise reducing pavements, we are lucky cyclists might get a bit of paint along the side...

Paul Martin said...

Great post, David. I remember standing on that very spot!

Yet another example of the benefits of physical separation from fast traffic. Thanks.

Green Idea Factory said...

Very methodical, but this ain't no "urban location", or is it? City streets do not generally have noise barriers. I would be curious to see this test in a big Dutch city.

I agree with noise barriers and attenuating road surfaces, unless of course they are the only measures, and e.g. just facilitate the same amount of fast traffic with its "tailpipe noise".

How much do the special pavements reduce noise, and where are these implemented and is NL continuing to implement them?

Mark Wagenbuur said...

@G.I.F. I think this would qualify as an urban location.
You can see it here. This is a motorway/freeway that goes right through Assen and both sides of the road are very urban.

Green Idea Factory said...

@Mark - Thanks, but my "urban" is lots of surface "street" traffic going by at 50 to 60km/h about 15m from my (often closed) windows.

r s thompson said...

"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. "

does noise reduce actual safety??

David Hembrow said...

GIF: It's a bit of a special case as urban locations go, as this used to be the edge of the city but the boundary was extended to include the motorway when the new housing area to the West was built.

Normal city streets are a bit different. Speed limits are not so high as the motorway, for instance. Despite this, the noise barriers remain. I've added a couple of Google Maps images to the blog post showing other roads in Assen which have noise barriers to prevent noise from rather lower speed limits from reaching residential areas. Also I added a link which has some details of expected reductions in noise level from different surfaces.

I can't think of any case here where there is a speed limit of 60 km/h on streets 15 m from residential windows. The speed limit would be lower than this, and that in itself decreases noise.

If you look at the noise map of Assen in a previous blog post you'll see that this motorway creates noise on the left of the city, and the railway creates one from the South to the North East, and that's about it. As you can see from this post, Neither really creates a huge amount of nuisance.

That roads and railways receive attention to make them quiet is part of the reason why there can be so many Stiltegebieden, or "silent areas" in a small country like this. We can cycle to several quite close to Assen and barely hear anything but insects and birds. This is true all across the country.

Mark: Thanks for the link. I've embedded it in the post now, as I should have done in the first place.

R S: It's interesting to speculate about what effect noise has on actual safety. I'm not aware of any such effect, so I wouldn't make such a link.

Lack of subjective safety certainly contributes to a reduction in the number of cyclists.

Green Idea Factory said...

Noise reduces safety because it causes heart disease (among other things).