"Average Speed" Speed Cameras.

And before I rant, I haven't had a speeding ticket. And I appreciate that they're supposed to reduce accidents. So don't complain. I am aware of that. However, there's one set in particular that bother me: on the M1, between the M25 and Luton.

There is road-widening going on, so there's barriers up between lane one and two (Southbound) and two and overtaking lane (Northbound). Lane one Southbound is having work being done on it (I assume, having never seen anyone working on it) and the overtaking lane Northbound is where the third lane of Southbound traffic travels (the Northbound using the hard shoulder).

Okay, so that was a complicated description, but I felt the need to describe the situation and emphasise the following: there are barriers. Big metal barriers with concrete bases. Between the road crew I've never seen and the inner Southbound lane. Another - the central reservation - between lane two and what would be the overtaking lane Southbound. And another one between the Southbound traffic on the Northbound carriageway and the rest of the Northbound traffic.

Barriers. Not cones. Barriers.

So why exactly does there need to be an average speed limit camera?

I spent more time looking at my speedometer than I usually do on motorways, which means I was spending less time looking at the road in front of me, or in my mirrors to see where other traffic was. Which is hardly an improvement in safety for the road users, as I'm fairly sure I wasn't the only one keeping more of an eye than usual on my speed. Lots of drivers looking somewhere other than the road in front of them doesn't seem an ideal situation.

And did I mention the barriers? They would seem to be a fairly effective method of keeping the road crews safe, seeing as it's a similar method to the one they use to keep the Northbound traffic from ploughing head-on into the Southbound traffic. So why bother with the average speed cameras?

Apart from probably generating enough revenue in fines to pay for the cost of widening the road, how is safety being improved? This is a genuine question. I can't find anything on Google which demonstrates to me one way or the other how having an average speed camera on a motorway actually improves safety. Please post anything that would help me get a better grasp on this, because at the moment I cannot see the point of them.