Diacritic (2021-10-24 02:42:35+00:00): Hey Supt,

Firstly, sincere thanks for your reply.  I appreciate the acknowledgement and effort to discuss these edits. I can see you are a prolific editor, and have contributed a very large amount of edits to the project for over a decade. It represents a considerable investment of your time and I do not in any way want to detract from that.

Rather than quote Wiki pages at you (I can see you've had those conversations before and have most likely already memorised the contents), I want to convey the significance of splitting ways, smoothing turn lanes, etc. Apologies for the verbosity; if I had more time, I'd have written a shorter comment.

Your reasoning for smoothing out roads to minimise 'clunkiness' is understandable, and logical. Maps are more than their functional value: they are representations of the world around us and help us understand the places we live. A lot of the micro-mapping on OSM seems to include adding individual trees, grassy areas and parks, because fundamentally people want their local area to look good on the map and consistent with their positive feelings to their local neighbourhood.

Fundamenally, maps are an abstract representation of a place. We use lines to represent roads, single colours to represent different foliage and a consistent blue colour for lakes and ponds, regardless of their actual variations. While it is certainly possible to create a map with those variations, instricacies and details, you would essentally be recreating a photo. No level of detail could ever make a map superior to a photo for a 1:1 representation of a place.

There is nothing wrong with smoothing a road to more accurately represent the geometry. I believe we share common ground on that regard. A road like https://www.openstreetmap.org/way/574151674 could be made into a smoother bend for both accuracy and aesthetics. We can add nodes to the road to make it look smooth, but if we zoom in more, we can still see the lines between the nodes. No matter how much we smooth the road, we cannot get the mathematical precision that the road engineers on the ground were able to achieve. I mention this philosophical point encourage you to accept that the map cannot, and will not, ever be perfect enough. Perfection is not for mere mortals to achieve. :)

With that in mind, consider a slip lane off a wide carriageway; such as this lane I picked at https://www.openstreetmap.org/way/157806869 at random. Human behaviour being what it is, some drivers will turn immediately into the lane as soon as it opens up. Others will wait until there is a wider opening before they merge. Others, (mainly BMWs in my experience) will slow down, stay in their lane before moving into the slip lane at the last moment. Buses might take a wider turning circle to turn into the lane, and motorcyclists might hug the left hand paint. How can we represent the paths all these drivers take with a single line? We cannot. Any line we draw will inevitably not reflect the behaviour of some number of drivers.

As long as we consider mapping roads as lines, and not areas, there is always going to be some level of awkward geometry at these points. And that's okay. We will never be able to be perfect, so we choose a method that represents the average of all changes, even if it might not be as smooth as real life.

Now, you might ask why, if perfection does not matter, that adding smooth turns is a problem. Surely they are no less imperfect than a "clunky" method.

Here we must acknowledge the way this data is stored and used. These roads are just a series of numbers in a dataset to a computer, even a very clever one. The computer cannot tell the difference between a smoothed turn into a slip lane and a fork in the road; a turn lane in an intersection from a separate road. For it, a line is a road, full stop. It may be possible to build a computer that can tell the difference, but OSM hasn't done it because it's really hard. Look at Google Maps, Apple Maps, Bing Maps. they all have the same "clunkiness" at the intersection I mentioned not because that is the most realistic representation of driver behaviour, but because it has proven to be the best way to represent and store road details. 

It is the way that GPS's, navigation systems and routing software interpret the data. It is the way that data consumers expect the data to be structured. It is the way that academic researches build their analytic models to examine. It is the way that geospatial analysts across government and industry use road data in real-world implementations and planning.

That is why the overly smoothed slip lanes, separate ways for turn lanes and overlapping ways are discouraged, and why you are finding that your efforts are being reverted or "simplified" back into the clunky version.

There is still significant value in adding detail to enrich the map, but I implore you to consider the points I've raised above and reflect on the suitability of your intersection practices. I'd also encourage you, if you haven't already, to discuss this further on the talk-au mailing list. There is a wider community there that is full of people much more knowledgeable on this topic than me.

Dian.