What is the minimum percentage of dimming required for flashing or sequential arrow boards during night operations?

The minimum percentage of dimming required for flashing or sequential arrow boards during night operations is 50%. This standard is in place to ensure that while the boards remain highly visible to drivers, they do not produce an excessive amount of glare that could impair a driver’s vision or create hazards on the roadway. Dimming the boards appropriately during nighttime helps in maintaining safety and enhancing visibility without overwhelming drivers.

This requirement balances visibility and safety, allowing for effective communication of road conditions to drivers without compromising night-time driving comfort. Dimming below this threshold would not provide adequate visibility, while exceeding it would likely contribute to glare and distract drivers. Therefore, the specification of 50% dimming reflects a critical safety consideration in traffic control management.