Possible Clues:

• The Buick stops here presumably for Amber
• Signal to a motorist?
• Can go green all of a sudden? That will hold you up!
• It can be red, yellow or green
• 22-Across sight
• Where to find the colors in this puzzle
• Business not strong, but one wants it to be green
• Device that signals the ends of 17-, 36- and 58-Across
• With a clear road it may still hold you up
• It may be red, yellow or green (2 words)