Have shared this tip with quite a few folks in 1:1 chats; it keeps coming up in various discussions, so I decided to write this up.
While planning a bicycle tour, one has to tackle the 'problem' of how to select suitable roads -- cyclists usually prefer avoiding highways, and heavy traffic routes, but if they are unfimilar with the areas through which they are planning to ride, they also wonder which alternate, back roads they can take.
To alleviate that problem, I have been using a trick for selecting routes, which has worked surprisingly well --
On any maps app, like Google Maps, set the "zoom level" to ~1km. At that point, any "interior" roads/paths that are visible, will be wide enough for a car, so they will good picks for a bicycle as well. If you are finding limited options, you can also go down to "zoom level" of 500m, to look for a road/path, and get options which work quite well for cycling.
This tip should work anywhere in the world, because it is simply related to the map scale, independent of the actual geography, or landscape. Ofcourse, this does_not tell you what kind of surface that road/path will have. And also, one needs to be careful to find out if those interior roads are safe, in general.
From my experience of cycling in diff parts of India (mainly south/western areas), I can say that this method will get you roads/paths with quite good surfaces, ~80-90% of the time. For the remaining ~10-20%, if not good tarred (or cemented) roads, you will usually get fairly smooth dirt paths, or fine gravel paths. Only in very few cases, maybe ~5%, you might get roads which have very bad surface (tar/cement roads in poor condition, or simply unsurfaced roads with lot of "rocks"); to the point where you may need to get off the bicycle and walk to cover that stretch.
If you are using an app like Komoot, you can check the elevation profile of various sections, to make sure you are_not picking a route which is very difficult wrt elevation changes / gradients. Or simply, to know in advance, the difficulty level of what you are choosing. You can use that info to reduce the "daily distance" that you are planning for those days.
Combining the above approach, with the info re: places -- towns, villages, eateries, etc. -- and natural features -- hills, forests, rivers, lakes, etc. -- available freely on Google Maps or other map apps, one can get a good a idea of what one can expect along those interior roads. Not to mention staying options -- lodges, homestays, hotels, resorts, etc. -- incase one is_not planning to camp. I have had very good experience, using Oyo, MakeMyTrip, and just Google Maps hotel search, to find places to stay, on-the-go. (To date, I have never camped on a bicycle tour; maybe that will change in the coming years.)
One can also use this to plan routes and stays, on a day-to-day basis, depending on where one is at the end of each day. But then do make sure you have reliable data connectivity; or atleast mobile voice call connectivity, so you can call and get a friend to help plan some sections/stays.
From my experience, in addition to your regular voice/4G-data SIM (which usually will be from some private service provider like Airtel, Vodaphone, Jio, ...), it is important to keep atleast one BSNL voice+4G SIM.
Additionally, a basic BSNL voice/2G SIM, in a basic non-smart candybar phone, is a very good final-backup phone option. On a tour in 2018, I was suprised that one evening, as I was ending my ride and looking for stay options, my Airtel and BSNL voice+4G-data SIMs were_not showing network/service, and it was only the BSNL voice+2G SIM, that gave service. So I could call a friend, have them search for stay options near my location, and send me some contact #s for hotels. Never thought I'd have to actually use the BSNL voice+2G SIM, due to service issues on the BSNL voice+4G SIM. The candybar phone was supposed to be backup, incase my smartphone ran out of battery. Either way, 2 backup SIM options was_not a bad idea afterall. Phew... :)
This bicycle tour route planning method has served me very well over the past 3years, giving me some very memorable multiday bicycle tours -- from ~3days, to ~2weeks. Very high percentage sections of those routes, I did for the first time, w/o any prior info from, or discussion with anyone re: specfics on what lay along those routes. Without this method, almost none of my bicycle tours of past ~3years would have been possible; since I am_not keen to "just take it as it comes" wrt roads/terrains on bicycle tours.
And on various day rides, where I have covered the same area on 2-3 alternate routes, I have seen that the routes picked via this method, almost always turn out to be lot more pleasant, and scenic, compared to the more regular roads; with almost no traffic. On very few occassions, I have had to backtrack to a regular road, because I ended up in some section where it was_not easy to go further.
So this has absolutely become my standard modus-operandi now, for selecting routes, when planning a day ride, or a multiday tour. Hope you find it useful as well.
Let me know what you think of this, especially if you try it out.
Happy and safe cycling.