excuse my idiocy but why do they have those big electronic signs that say "Junction 8, 15 mins"

Paua oouaarancì Irà chiyeah Ishé galé ma ba oo ah

Based on current traffic conditions, it's the ETA at the named junction.

I thought that was the obvious answer I just don't understand the neccesity

Paua oouaarancì Irà chiyeah Ishé galé ma ba oo ah

I suppose it's kind of comforting to know that you'll be somewhere in 15 minutes.

What else could they show on those big screens? The FA Cup Final perhaps?

Denial is not just a river in Egypt!

They do it to encourage drivers to relax and not panic if they hit a bit of traffic. The M25 in particular had a history of wave motion where people accelerate too hard and then slam the brakes on. That is part of the reason why sometimes the speed limit seems lower than necessary on the variable sections. Overall the traffic runs quicker on average, just slower for most of the time.

They really do their utmost to distract drivers nowadays.

If it's not pointless info like the OP said, it's f***ing about with the speed limits every 500 yards so you spend more time watching the speedo than the road ahead. They also have a giant video advertising screen next to the M25 when we don't even have static billboards on them usually.

What would be helpful is information screens before you get on the motorway, to tell you whether traffic is flowing well or not. As for the lights they've put on the slip roads... Great you've let me come down the slip road and now have me waiting at a red light cos the motorway, that I still now have to join, is utterly f***ed.

Optimistic as ever