Understanding the Purpose of Redundant Traffic Signals at Intersections

Traffic signals are crucial for ensuring safe and efficient movement at intersections. At many of these points, you may have noticed multiple signals facing the same direction and giving the same indication. This article aims to explain why such redundancy is necessary, highlighting important benefits such as enhanced safety and reliability.

Redundancy for Safety and Reliability

One of the primary reasons for having redundant traffic signals is to ensure reliability. In the case of one light being burned out or obscured, the remaining signals can still guide traffic safely. For example, in large junctions, repeater lights are often placed above each lane to provide backup signals. Additionally, one light is usually mounted higher, making it visible even when a large vehicle blocks your view at a distance.

Improving Visibility and Blocking Line-of-Sight Issues

The line-of-sight aspect is another critical factor. In some intersections, especially those where streets have cornering or where trucks block your view of the signals, two signal heads on the overhead mast arm can improve visibility from a distance. However, following a large vehicle too closely can still result in one or both signals being blocked. For instance, if a truck is in the right-turn lane, it might block your view of the signal heads. To mitigate this, placing one signal head on the mast-arm pole and adding a third on the pole can further enhance visibility.

The MUTCD Requirement

The Manual on Uniform Traffic Control Devices (MUTCD) mandates redundant signal heads for the major traffic movement at signalized intersections. This standard is crucial for maintaining intersection safety. Take, for example, a recent incidence where the right-hand signal head was out. Despite a lack of redundancy, the left signal head still provided the necessary information to stop. This redundancy is essential because a single signal can cause confusion if a driver incorrectly assumes they have a green light and enters the intersection, which could lead to a T-bone or broadside collision.

Real-World Experience

From a personal perspective, following line-of-sight issues and blocking can lead to precarious situations. Approaching an intersection, especially one with a right-hand curve, might make it challenging to see the primary signals until you are almost at the intersection. Defensive driving involves backing off if there's a delay or if you notice a potential issue. In such cases, relying on the redundant signal can prevent a collision.

Conclusion

In summary, the presence of multiple traffic signals at the same direction enhances safety and reliability at intersections. Whether it's redundancy for backup during signal failures, improved visibility due to blocking issues, or meeting the MUTCD guidelines, these redundant signals play a pivotal role in ensuring that intersections operate smoothly and safely. Understanding these design choices can help drivers make better decisions and avoid potentially dangerous situations.