This image is OTTD
The question here is why there is no road sign of direction indicating of both sides towards the same direction in Simutrans?
Is it not as good as OTTD?, or Is there much advantage in development time?
Some more development effort will be necessary to make the actual function (two road vehicles driving in parallel into the same direction) possible. It's not sure whether this will happen. Graphics are not the problem with this.
Exactly, ST is much better! ;)
Well, both have advantages and design limitations. It's not the goal of this community to copy another program.
You can use one-way signs at the entrance/exit to a road to achieve the same effect.
Only to a very limited extent - vehicles may overtake each other under certain conditions, but they are not able to fully use both lanes.
As they will do in OpenTTD, if I remeber things correctly ...