Traffic and pedestrian signals rely on the power grid, so it’s not uncommon for signals to go dark or experience power failures. Often, these power outages occur during severe weather or high winds. They can also occur due to poor wiring, grounding issues or bad transformers.
Dark intersections confuse motorists and increase the risk of an accident. This is especially true for streets with four to six lanes and for intersections with turn bays. In these cases, the right-of-way can be ambiguous without a traffic signal.
The response to these problems varies from waiting for motorists to report the outage to installing portable generators. The response may depend upon on the cause of the outage and the notification time. Let’s take a look at how to identify and address these problems.
Prevention Strategies
The best way to address power problems at intersections is to prevent them in the first place.
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Backup power is not required under federal guidelines, but it can prevent dangerous power problems. If the power goes out, a battery-powered traffic signal can revert to a flashing mode. These flashing signals are much safer and more effective than dark intersections.
Backup power is most impactful near certain places:
- High-volume intersections
- Signals with a history of malfunction
- Intersections with preemption requirements
- Areas where repair times exceed 30 minutes
- Intersections with high-speed approaches
According to a California Department of Transportation study, traffic accidents fell by 90% at intersections with battery backup. Battery costs have also fallen as gel cells replace lead-acid batteries. These batteries don’t need extra safety cabinetry, saving $700 or more per installation.
Remember that backup power systems still need regular maintenance. For example, most batteries need replacement every three to five years.
Smart City Technology
It may not be practical to install backup power everywhere, and even the best backup power systems aren’t 100% reliable.
Most cities use some form of a central system to track their assets. But it’s expensive to connect intersections to a central system by laying new fiber or phone lines, and agencies have no way of monitoring the status of non-connected intersections.
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New technology is making it easier than ever to connect an agencies’ assets—including traffic signals.
The Glance Intersection Monitoring System is a simple, non-intrusive solution for traffic signals. Using a cellular modem, it feeds vital information into the Glance Smart City Supervisory System for technicians to monitor. Continuous monitoring reports problems as soon as they arise—without the need for costly on-site inspections. Wiring problems or dark intersections can be proactively identified and repaired.
For example, the Glance system monitors power levels ten times every second so technicians can detect sudden spikes and small brownouts. This data can give them a much better picture of what’s happening at the intersections and help them determine the root cause of the outages.
Key benefits to this technology include:
- Instant status change notifications via SMS/Email
- GPS-enabled self location
- Exact status and location information for service personnel
- No need for costly regular inspections
- Built-in battery backup
- Logged performance and activity reports
The Glance Smart City Supervisory System provides a web-based system to manage all these traffic signals. You can see exactly which intersections are causing problems and go to utilities with the right data to fix it.
Contact us for a consultation to learn more and/or download an information kit.
Responding to Outages
A power outage at an intersection requires an immediate response to avoid accidents. The longer the response times, the greater the risk of injury or death. It’s important for all cities to develop a dark signal policy to guide their response.
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The three most common responses include:
- Wait for Someone to Report It: This approach is common when authorities have no way to monitor the status, and it can result in lengthy outages.
- Police Control or Folding Stop Signs: Police officers or temporary stop signs can help control traffic. Once power is back, it’s important to remove these signs to avoid confusion.
- Portable Power Supplies: Fuel-powered generators can help supply power during an outage. These generators are usually in short supply and need regular maintenance.
Specific policies may vary depending on existing traffic laws and the intersection. For example, dark intersections may become uncontrolled intersections in some areas. This can be confusing for drivers expecting a four-way stop. It may be necessary for intervention in these cases to avoid an accident.
The Department of Transportation further suggests the following policies when using folding stop signs:
- Explicit procedures for emergency responders to set the signal in the signal cabinet police door to flashing mode before unfolding the STOP signs. The signal shall be visible to traffic on all approaches and all of these approaches will be flashing red upon restoration of power.
- Upon restoration of power, the emergency responder shall refold the STOP signs so that the legend is not visible to approaching traffic and then to restore signal operation in accordance set forth in Section 4D.12 for transition from flashing mode to steady mode.
The key is fast decision-making when a problem surfaces. By having a written plan in place, you can cut response times and reduce traffic accidents.
The Bottom Line
Traffic and pedestrian signals often rely on the power grid. Without backup power, they may go dark for several hours during severe weather. Malfunctions may also cause issues with traffic signals.
Backup power is a great preventative measure to avoid going dark during outages. If an intersection does go dark, smart city technologies can fire off detailed alerts. These alerts can help service personnel improve their response times and cut downtime.
It’s important to plan for dark intersections, even if you have backup power. The plan should account for all scenarios, including short- and long-term power interruptions. With these plans in place, your intersections can be safer for motorists, even in emergencies.
