SCARM software has a feature for creating these. free.
http://www.scarm.info/blog/advanced-techniques/how-to-make-control-panels-and-diagrams-for-scarm-track-plans/
A CASE course at work taught me that unless you get a drawing package for the type of drawings you want to make, it may be very frustrating to use any "do-it-all" type of package. I assume a good CAD program is not cheap and may still not be easy to use for railroad schematic.
I think some graphics paper, ruler, pencil, scissors, tape and a big eraser, would be a good way to get started that would keep you focused on accurately developing a schematic, instead of spending a lot of time trying to figure out how to use an unfamiliar drawing package. Once you have a sufficiently complete representation of your railroad, you can redraw it neatly, or maybe get someone who is familiar with a drawing package to re-draw it.
I assume the image below is what you mean by schematic and can probably do neater. But the schematic below covers an awful lot of territory and provide a lot of interesting details.
greg - Philadelphia & Reading / Reading
If you just want a straight line schematic, Inkscape is a good option for that. And best of all, it's free!
https://inkscape.org/en/
Steve S
After nearly 3 years of building my railroad, I am ready for my first operating session sometime this summer. I would like to draw some type of schematic of the railroad and give it to each of my operators to look over and carry with them around the railroad during the session. Do I need some type of CAD program to do this with? I have no experience with these programs. Is there a simple way? Any advice on how to do this would be appreciated.
Thanks, Rob