The problem often is caused by the following:

1) Poor road design - either the slip-off is too short and cars moving along in lane two realise very late on that to slip off, they have to cut across other road users, OR, as seems to be increasingly the case, the 'slip off' is really just another lane for a mile or so, implying the minute the 'filter' sign appears everyone slipping off should be in that lane, despite the slip off itself (i.e. where it diverges from the motorway etc) being some way off.

Examples of the former are often found on 'old' dual carriageways, particularly in rural areas, and I've heard of accidents when people brake too late and cause following vehicles to swerve and crash, or side-on ones due to people cutting in. For the latter type, there's quite a few local to me in Hertfordshire (the A1 Southbound slip off at Stevenage North and other side of the road Northbound at the Letchworth/Baldock junction slip off), but BY FAR the worst I've come across is the M4 eastbound slip off to the M25. Lane 1 always full of traffic, no-one leaving any room and others bombing along till the last moment and cutting in, causing bunching and near misses.

Both sets of drivers are at fault, but its all brought about by poor road design. Needless to say, traffic jams on lane 1 even build up outside the rush hour, not because of too much traffic on the M25 either, as at that time lanes 2-4 on the M4 are almost empty and the M25 is flowing nicely, including at the slip on.

2) Poor driving, as shown above. People leave too little gaps and accelerate and brake hard to stop people in the second lane from cutting in, causing bunching and more hold-ups behind, impeding the flow of the queue. I agree that it can be very dangerous for people to slow to a crawl/stop in lane 2 (especially at the end of the slip off), but its also partially the fault of following drivers not paying attention and moving to lanes 3 and 4 (if available) early enough if they are not turning off.

I think the situation would be improved a bit at least if the slip offs on junctions for two major directions (e.g. the M4 Westbound to M5 north/south, similarly for the M5 end changing to the A30 and A38 just after Exeter) to have signed twin lanes for each direction early enough for traffic to get in the correct lane, though not too soon for the reasons stated above.

The aforementioned M4/M25 and A1 junction 'slip offs' are, in my view, not just useless, but downright dangerous, particularly at noght and/or in poor weather conditions. I myself have had a few near misses, and to be honest its difficult sometimes when the slip road is very long to decide whether to continue on (even if you can see gaps forming up ahead in the slip lane) or get caught in a very long queue for many minutes and still be at risk for idiots cutting into gaps that aren't there. I normally pull in early, but it can often be a very frustrating experience...

Unless there's an accident blocking the road ahead (that's minor [no injuries or risk of the vehicles moving, leaking fuel etc or catching fire/exploding), I may think of using the hard shoulder to pass if the remainder of the traffic in lanes 2 and up isn't slowing down enough to allow me and other drivers to pull out and around, but I would only do so if I wasn't a material witness to the accident, needed to help or was too far back (which would encourage other drivers to do the same). Probably not a good idea if people are milling about outside their vehicles - as I say, it would be more to get my car out of the way to avoid secondary accidents happening from others who can't see what's happening from a long way behind in other lanes.

I think that the removal of the hard shoulder is patently stupid, as it can often lead to cars being stranded in occupied lanes (rare for cars to make it to the 'refuge' points, because its not easy to see where they are, especially if your vehicle has a serious fault and you need to pull of asap), accidents and mostly huge tailbacks as a result of one lane being rendered useless for a mile or so when the Traffic Officers temporarily cone it off, assuming they can actually get to the scene, as their normal route is often blocked.

As an example of this, last year I was on my way home from holidaying in Cornwall, driving along the A30, and there was a serious accident ahead (unfortunately it occurred after the last turn off before the M5 starts/first slip off for Exeter) and so, because it was a dual carriageway with no hard shoulder, the emergency and recovery vehicles had to get through 5-10 miles of queuing traffic to get to the scene, meaning that to get everyone treated enough to be stable for travel to hospital and recovery/cleaning up/noting the scene took best part of two hours, which, compared to some major crashes on the motorways, isn't that bad (fortunately nobody seriously hurt or chemical spills/artic lorries shedding their loads).

Still, if there was a hard should, or at least a 'crossing point' further along for emergency and recovery vehicles to get to the scene more quickly, the situation would've been resolved in less tha half the time. I felt sorry for one guy ahead of me - he had some food shopping that (it was quite warm that day) was rapidly defrosting!

Edited by Engineer Andy on 05/12/2017 at 11:28

Any thoughts ?

Drivers have always ignored the rules and made up their own as they go along.

"....BY FAR the worst I've come across is the M4 eastbound slip off to the M25. Lane 1 always full of traffic, no-one leaving any room and others bombing along till the last moment and cutting in, causing bunching and near misses.` -+`"

I'm not defending people who do that, but time and again I've driven past that junction and seen big gaps immediately before the turn-off, and people turning into the left-hand lane without actually cuting in and causing anyone else to brake. Some drivers insist on braking and queuing too soon, and I can understand why others are willing to take the chance.

not sure if it is poor road design, ot planned usage, look at the A406 extension between the foot of the M11 / junction of the A12 up to the A13. The road has 3 lanes for both directions but for every junction lane 1 dissapears to the junction whilst lanes 2 & 3 continue to bidge over the junction below.

So lane 1 has lots of queues, the through drivers use lanes 2 & 3 .... even when lane 1 is free so encourages middle lane use / hogging to avoid switchng lanes / danger of being caught in lane 1 unable to move to lane 2 if not wanting to exit.

As for using the HS as a waiting lane at motorway junction, about 2 weeks ago on M2 J6 (Faversham) London bound there was a queue to leave to gain access to A251 towards Ashford. The queue was caused by roadworks on the A251, this is a glorified country lane so there were traffic lights and all traffic shared the one side of the road. I found myself a long way back before the slip road stationary in lane 1, I dialled 101 to advise Police of problem, the lady who took the call was disinterested bordering on rude ... if there had been an accident this would have been an interesting matter to bring before the coroner ....