Marking as solved, travelling on the M4 westbound this junction now behaves as expected. Thanks to all involved in looking at this junction.

You raise some valid points. As often, there is no “right” answer, just a series of compromises.

1) the junction has been deliberately configured so that drivers staying on the M4 get an audible instruction to stay on it. As you have noticed, this has the effect that when joining the M4 in London with the intention of going all the way to South Wales, you drive across England with an instruction displayed to keep right at this junction rather than exit at your Welsh junction.

The rational for this is that only 2 of the 5 lanes continue on the M4, and it would be easy for someone doodling along in a left lane to get onto the M5 by mistake. This is achieved by the lane guidance specifying “view and hear” for continuing straight on the M4, rather than “view only”.

My personal preference would be to change to “view only”, which would cause you Welsh exit to be displayed for most of the journey, with a display (but no audio) indicating taking the right 2 lanes for a short distance (1 mile?) before this junction. I’ll ask other senior editors for a vote on whether they think this would be better.

As an aside, if we do stick with “view & hear”, I think the display should be amended to show the junction number - 20.

2) the lane guidance shows 5 lanes but first appears when there are only 4 lanes.
Unfortunately the lane guidance appears a set distance before the junction, and we have no control over it. There are five lanes for quite a while before the junction, so I think it is better for lane guidance to show 5 lanes. I agree it would be better to show four for a while and then five, but I don’t think we can achieve this (without introducing a fake extra junction, which certainly would be over-engineering).

3) It is very clear from the signage that you should use different lanes leaving the M4 depending on which direction you are going on the M5. However the final split between the M5 directions is well after leaving the M4. This creates the risk that a slow and careful driver (if any such use Waze ) heading for Gloucester might correctly leave the M4 in lane 3, and then move into the “slow lane” before the M5 ramps diverge, thus getting on the M5 in the wrong direction.

The “roads to nowhere” which you highlight allow Waze to give the “lane 3 of 5” instruction on leaving the M4, and then a separate “lane 3 of 3” instruction where the M5 ramps split.

In summary, I’m inclined to agree that it would be better not to have an audible warning for drivers staying on the M4, but otherwise I think it’s mapped as well as Waze tools permit.

I’ll try and get some other senior editors to reply too.

Ian
 
 

I've responded to BeRoWaz on the UR near here, and advised to post in the forum for views other than mine, hence this thread.  So my two pence is similar to your point no. 1 ditchi, but I would be inclined to leave it as View and Hear, instead of View Only.   Its more than just a single lane drop here, its a major intersection of motorways.....I would be grateful for a voice instruction here as well as visual if I was unfamiliar with the layout.