When should 叉 or 岔 be used when talking about a forked road?
There's a similar question here:

https://zhidao.baidu.com/question/326153419.html

that asks:


  岔路口 叉路口有什么区别 


the answer reads:


  岔路口有方向概念，也即你面朝的方向有两条以上的分岔路；叉路口（一般不这样叫）一般称为交叉路口，指两条以上的路相互交叉。


岔 = forked (road) like this:



the road splits in front of you, like crossroads.

叉 = intersect like this:



like a junction or an intersection.