Is this sign obscure? What is it really trying to say? After looking at it for a while, you can tell that it just means there is two way traffic. This is a good example of unintended obscurity. Wouldn't it have been easier to just have a sign that said two-way traffic?
Unintended obscurity in writing is basically the same. A writer in the quest to be descriptive and insightful sometimes writes exactly what they think. Therefore, many times their writing is full of convoluted sentences that are hard to understand.
To avoid this pitfall, always edit your work and weed out unnecessary words. If possible have someone else read it to see if they understand what you're trying to communicate. Another pair of eyes can save you from unintended obscurity.
Now there are times when writers intend to be obscure. Think about legal documents. To me, that style of writing is intended obscurity. It's confusing on purpose, and you need a lawyer to explain what it means.
However, in general, writers need to avoid obscurity and write well-crafted sentences.
Can you think of a fiction writer whose writing is obscure on purpose? Off hand I can think of several, but I want to see if I'm the only one.