In the TikZ manual, version 3.00, the "double" option for line styles is discussed on pages 170 and 171 immediately before the section "Adding Arrow Tips to a Path". We see an example of an arrow tip, "implies", that looks good combined with the "double" option, but it is not clear to me whether other arrow tips may be made to work well with "double". Here is a document that tries four ways to get a double line with arrow head, and the output I got (zoomed in a bit).

The bottom one is the one that best shows off what I want to achieve, but it is also the least easy to understand from the code. If you are wondering where the different \sep values are from, the first is the default value specified on page 199 and the second was arrived at by trial and error.

Is there a better way than what I came up with here, of getting a double line with matching arrow head?



        \draw [very thick, red, double = white, -{Stealth}] (0, 3) -- (1, 3);

        \foreach \thickness/\colour in {ultra thick/red, very thick/white} {
            \draw [\thickness, \colour, -{Stealth}] (0, 2) -- (1, 2);

        \draw [ultra thick, red, double = white, -{Stealth[fill = white]}] (0, 1) -- (1, 1);

        \foreach \thickness/\colour/\sep in {ultra thick/red/0.88pt .3 1, very thick/white/1.8pt .3 1} {
            \draw [\thickness, \colour, -{Stealth[sep = \sep]}] (0, 0) -- (1, 0);

Document output, zoomed in

I apologise if this question has been asked and answered already. When looking for questions that relate to "double" and "arrows", a lot of unrelated questions relating to double-ended arrows are found.

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