>>96416120
>or roads that only contain line heads running opposite to the line extension.
not how that works

if the end of your line is at the same intersection as a another player your line can expand through any street containing their line
it does not have to be the street where the end of their line is coming from
e.g. blue expansion in pic
but this does not allow you to expand on roads containing multiple players if only one of them has an end of the line at your intersection

the exceptions are also independent from one another
even if you have options because of the end of a line you can still go on any road you want at a full intersection
e.g. yellow expansion in pic