On my layout, i added some rust streaks to the signs for extra realism.

This image shows how the signs look illuminated by HO scale car headlights. The added grime/rust can be seen in this image too.

The weathered signs look convincing, and you can add some foliage nearby to help them look like part of the environment.

Another shot showing how real the signs look at 'night'. This was before the nearby trees were installed. I get lots of complements on these signs.