Hello and welcome to More or Less on the BBC World Service with me Ruth Alexander. This

is the programme all about numbers and statistics in the news and in the world all around us.

And this week in the oceans.

One of our listeners, Philip Biggnorm, has written to us with a question about the high

seas.

There has been quite a lot of press in recent weeks about people traffickers and a swimmer

in the English Channel, the Straits of Dover. There's usually the additional comment

that it's the busiest shipping channel in the world.

Well, is it?

Whenever I've used the channel ferries, there seems to be no difficulty to get through to

the other side.

We're going to answer this question and uncover lots more about busy shipping lanes this

week. Shipping lanes are usually routes in the sea or in large lakes that are regularly

used by vessels.

The English Channel is the body of water between southern England and northern France. It

links the North Sea with the Atlantic Ocean.

To start off, we thought we'd look at how ships are detected and counted. One way of counting

ships is to use something called AIS, an automatic identification system. It lets you see what

vessels are in the vicinity. It's mainly used as a navigation safety system and works

really well for areas like the English Channel.

While there's no single source of data for absolute numbers of all vessels sailing through

shipping lanes, there are some numbers which can give an idea about which of the busiest

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