Bravo2zero_sps

Over the last week a large number of cameras have been placed on the North bound carriageway of the M20 running from the bottom of Wrotham Hill to the top up by Brands. They are placed roughly every 400 metres on very high poles. Two are also on a sign that bridges the motorway pointing in opposite directions. They are definately not speed cameras like the ones on the M1 currently that monitor your average speed.

What are these cameras used for as I can't see its for traffic monitoring as this stretch of the motorway never clogs up at any time of day? Why would you need one every 400 metres over a couple of miles?