Seeing AndyPot’s post about Hemel Hempsted has brought back to my mind a discussion we had about when is a slip road not a slip road, which didn’t come to a conclusion (as I remember).
To my mind, these segements are part of the A55 PRN as they both run directly from the A55 to the A55. The confusion is caused by the manner in which the road splits making it appear that the slip road to (or from) the A494 is the continuation and that the straight continuation of the the A55 carriageway becomes the A494 and that the A494 direct route travels for a couple hundred of yards as the A55.
I can’t even describe it very well.
I think the problem lies in that we find it hard to consider something as carriageway rather than slip road if the two directions of the carriageway separate by anything more than 10 to 20 metres.
This layout always looks rather odd to me in the Live Map as the joining road appears to stop short of the junction - it’s also particularly difficult to see the ramps to/from the Westbound carriageway as these are set to Elevation -5 … I see this a lot with slip roads, anyone know why?
This is the case even without the change of road numbers you have in your example.
Here’s another junction on the A3 with the same ‘gap’.
I’m sure an expert will confirm but I think the Ramp segment is required to generate an ‘Exit’ instruction if there’s no lane split rather than ‘Keep Left’ but you could retain a short segment to do this perhaps.
Yes what happened to that, couldn’t really get anyone else interested.
I would include the junction just to the west as well so in my mind all these segments should be Primary Routes not sliproads.
To me the primary issue is aesthetics, it doesn’t look right in the client if the road stops short of the junction, then there is the secondary issue about what is technically correct.
The Wiki talks about road splits. I gave an example previously of the A6 which is a two lane dual carriageway south of Derby that splits where it joins the the A50, the left lane goes east and the right lane goes west, there are no slip roads leaving from the side just a split between the two carriageways. Surely there can’t be any argument with that example.
To me a slip road is a separate lane that verges off from the left AND ends at a roundabout or T junction, somewhere where I have to “Give Way,” if however it merges seamlessly into another road then I don’t believe we should map it as a slip road. A good example of this is the A40 where it leaves the M40, I wouldn’t draw a slip road but in Waze (and Google Maps) we have a 1.5 mile slip road that then just becomes the A40, why 1.5 miles? Why not 1.5 feet? There is no difference in the road surface, no obvious markings or changes. In actual fact all this section is really still the M40 which actually ends at he first junction of what most people probably assume is the A40.
I would propose that we class the junction as a road split if the slip road merges into another road without passing a give way sign. In other words you can travel through the junction at speed (and not just because you are a nutter) without having to give way or yield to other traffic. Therefore all the examples given above are road splits and should be mapped without slip roads and that includes the A3 examples from PealRinger.
Andy.
I think this is why agreement is hard to come by. You and I are in general agreement over this and yet I would agree with the two to the west actually being the A494, however I would say these two are slip roads from the A55 to the A494. This is because I don’t like two sections of road (in the same general direction) having the same designation. The authorities that manage the roads don’t seem to have problems with it though. That being so I would rather go with Andy’s definition than the way things are currently.
Purely from an aesthetic point of view, I’d prefer to see more red than green at these kinds of Major Highway to Major Highway junctions.
Ramps are for ‘grade separated junctions’, and are named in a particular way. Those names are then hidden from the map.
For Motorway and Major Highway splits, ramp names are not required, and so don’t need hiding.
I don’t think anyone really notices whether it says ‘keep left’ or 'exit left.
…or more blue than grey in the ‘Roads Experimental’ layer. 
Does this mean that anyone L4 and above can enact this and the rest of us can ask in the editor requests forum? Or do we need further discussion or clarification?
Cheers