There are two nominal sizes for signal lenses: 8-inch and 12-inch. SDDCTEA recommends using 12-inch lenses in most cases, and always:
- Where arrow signal indications are used
- When intersection approach speeds exceed 40 mph
- Where signals are over 120 feet from the stop line
- For approaches where signals might be unexpected or sight distance is limited
- For locations where there is a significant percentage of elderly drivers
All new signal faces shall use 12-inch signal indications except as provided for in MUTCD Section 4D.07.