Apologies for the delay.
Ok, that makes sense. In that case the (live) sectional appendix is probably your best source of info but I'd also make contact with the Network Rail gauging team and ask for copies of the "Certificate of Gauging Authority" for each class of rolling stock. This would give a bit more detail including temp stuff and would give you a better understanding of what some of the restrictions are for, plus which are long term or might dissapear soon and/or what's potentially changing in the future.
If you're doing that kind of a product you absolutely need to foster a good relationship with Senior Gauging Engineers in Network Rail. I'd also advise re stronger insurance than the basic stuff - if you are selling a system rather than your personal services it's probably a bigger deal, but as others have said you'd need to show something robust before anyone will use it.
I'm not at all saying don't do it - innovation and development is fab, just be aware of how risk averse train operations planning can be and try to get a good understanding of the market you are entering, ideally before spending a lot of time and/or money on setting up a system that then may go nowhere (but hopefully wont).
What's your target market? TOCs? NR ops (day to day)? NR timetable planners? TOC timetable planners? NR Capital Delivery? All of those? It sounds interesting and potentially useful.
I have thought about temporary gauging certificates and other items such as SoCs and RT3973 forms but it'll be hard to maintain the data without replacing the source data and processes. I do separately map permanent gauge certificates in a way that separates what's published within NESA and what's on a gauge cert.
I'm not planning on doing any commercial products with my maps and data. Currently, I share publicly my gradient and electrification maps as well as a tool for shows gradient/electrification breakdown for a specified route. A lot of people on this forum put in a lot of effort to track electrification progress and creating the maps is my way of contributing.
One of my planned projects is to create an API that can allow developers to retrieve the gradient and electrification breakdown data. In the future this could include line speeds and curvatures along the specific route (provided by origin, via and destination tiplocs/stanox). This data can be used for any project (i.e. emissions research) but I have specified to not use it in safety critical applications because it's not had any sort of official approval by NR, and I can't guarantee the gradient data for example to be 100% accurate.
I'm sure the gradient data is about 98-99% accurate but with me just saying 'I'm sure', isn't going to cut it - as mentioned above. So I have the data, I want to share the data (for free) but I also want to make sure I'm covered just in case someone does use it in a safety-critical environment or it does cause some financial damage. I don't think "Use at your own risk" would suffice but it is the only source of truly digitised version of a combined data source out there. I do have plans to have a second pass at the gradient data to fix a few issues I'm aware of and I'm human, so there may be others that I will catch.
In regards to the rest of the data such as Loading gauge, route availability, locomotive/stock clearances, max weights, max lengths, etc. That's primarily used for my research but I do share access to the maps for those in rail who are interested. There's a couple of people in NR, DfT, TfN, RFG and a couple of operators that have access to the maps but they are aware of the conditions i.e checking NESA if they plan on doing anything. You can do a lot of commercial applications with the data such as improved path planning and validation, analytics, strategic planning and other fun stuff.
I've been in many meetings with Network Rail and some operators since I started in 2016. Data maintenance was bought up a lot (understandably) as rail is safety critical environment and it's always good to follow data standards i.e. ISO 8000. Since those meetings, I've taken note and re-evaluated all my current processes and tools to ensure data quality are fit for purpose for both the short and long term. I recently do have the means to make the data match NESA 100% automatically which means that if NESA has a mistake, then mine would show it too. Although there is an instance where a route is W6A and W9 cleared but not W7 or W8. I do fix those as they are static gauges (after some consultation).
Either way, even though I'm sharing the data and can have every caution sign on the planet. I still want to protect myself.
On this point, it's worth talking to TOCs and NR about what the systems they currently use can theoretically deliver, in time.
For my current work, I've been doing that since I started. For the long-term plans, I've been expanding on those efforts quite a bit but mostly systems within NR.
. Since those meetings and going back to solo work, I've developed a lot of processes and tools that help maintain the data. By changing a few lines of code, it can 100% map the data exactly to how NESA displays the data including the restrictions (even if there's mistakes within NESA). I typically run the tool at least once a month.