Green Light Lincoln

Green Light Lincoln is a Transportation initiative that has updated Lincoln’s traffic system and resulted in a wide range of transportation, economic, and environmental improvements that increase people’s quality of life. The project offers better traffic flow to improve safety, a reduction in congestion, fuel savings and improved air quality in Lincoln.

Results

Annual benefits resulting from signal timing and equipment upgrades include the following performance measures:

61.8 million vehicle stops eliminated 1.3 million gallons of fuel saved annually 1,215,200 vehicle hours of delay saved annually $23.7 million dollars saved annually 121,700 kg of vehicle emissions (133 tons) prevented

There are several key components of Green Light Lincoln that are connected to the Lincoln Transportation and Utilities Traffic Management Master Plan. Key benefits of this initiative are wide reaching and include:

  • Reduce the number & severity of crashes
  • Reduce travel times, delays & stops
  • Reduce vehicle emissions & pollutants
  • Reduce fuel consumption for savings at the pump
  • Smooth traffic flow & reduce driver frustration
  • Delay the need for major street widening projects

Each phase of the project consisted of improvements to signal equipment and signal timing at the 410-plus signals across the City. The City will continue to review and update Green Light Lincoln every three to five years.

Upgrades included improvements to the following traffic signal system elements:

Intersection Detection Systems More info Signal Displays & Phasing More info Intelligent Transportation Systems (ITS) More info Traffic Monitoring & Incident Management More info

New Intersection Detection Systems

The majority of traffic signals have equipment (“detectors”) that tells a computer when traffic arrives at the intersection, so that traffic can be given a green light. Detecting arriving vehicles can be achieved in a variety of ways, but some are more reliable than others.

Some previous practices are not necessarily the most cost effective or reliable means of providing detection over the life of the traffic signal. The traditional detection practice in the City was using inductive loops. Inductive loops require a ‘coil’ of wire to be placed in a sawcut or under the concrete. When a vehicle enters the magnetic field of the loop, it places a “call” into the computer telling the intersection that a car is present. Potholes, pavement damage and even seasonal changes where the concrete or asphalt contracts and expands can cause the loop wires to be broken. When the coil of wire is cut or broken, it tells the computer that there is always a vehicle present even if it is not. This results in the intersection calling up the green or holding it too long for no reason.

The City has standardized the use of more advanced technology for detecting vehicles, relying on video and radar detection equipment. Occasionally inductive loops will be placed under newly poured concrete, but inductive loops are no longer allowed to be sawcut into existing pavement.

Signal Displays and Signal Phasing Alternatives

The City primarily uses flashing yellow arrows instead of protected left-turn movements (solid green left-turn arrows) to better accommodate flow for oncoming traffic. Flashing Yellow Arrows, which are becoming the new nationwide standard, are showing an increase in traffic flow.

Intelligent Transportation Systems (ITS) Deployment

Intelligent Transportation Systems (ITS) equipment is extremely helpful for making adjustments to the signal system. Installing more Pan-Tilt-Zoom (PTZ) cameras, bluetooth devices, Wi-Fi devices, and dynamic message signs (DMS) lend support to making quicker and more efficient changes to the system as traffic conditions warrant. Additionally, the City has installed current generation signal control hardware at all signal locations and computer software for greatly improved performance in managing the traffic signal system.

Traffic Monitoring and Incident Management Capability Improvements

The City constructed a new Operations Center to better administer this new technology and provide quicker and more efficient responses to various incidents and events throughout the city.

Since the beginning of 2018, the project has included the areas and corridors highlighted in the map

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Travel time runs were performed to calculate the above performance measures. To learn more, watch the side-by-side video comparison of travel time runs on “O” Street before and after Green Light Lincoln signal timing and equipment upgrades.

YouTube video

The resulting benefit-to-cost ratio is 17:1

The Federal Highway Administration (FHWA) recommends that signal timings be updated every five years. Based on the FHWA’s recommendation and assumptions, Green Light Lincoln is expected to deliver these benefits annually. Total annual savings resulting from the project to date are expected to be $23.7 million.

Final Reports

Frequently Asked Questions

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When did this project take place?

Green Light Lincoln kicked off January 1, 2016. Implementation of Phases 1, 2, 3 and 4 were completed by 2020. The Phase 4 report was released in 2021.

Why can’t we flash the lights at night like other cities?

The use of late night (off-peak) flashing operations was evaluated as part of previous phases.

As it currently stands, Lincoln does not implement late night (off-peak) flashing schedules for the signals. The industry has leaned away from this in recent years, based upon recommendations from Federal Highway Administration (FHWA) regarding safety concerns.

It comes down to a benefit/cost issue. The bottom line is there will be many updates to signal operations resulting from Green Light Lincoln, but they will be data driven, and based upon best practices, and latest industry standards.

Why did we change to flashing yellow arrows?

These signals are being introduced nationwide because of their safety and operational benefits. A national study conducted by the Federal Highway Administration demonstrated that the flashing yellow arrow helps reduce left-turning crashes by up to 25 percent, moves traffic through an intersection more efficiently, and provides more flexibility in traffic management. More information about the new signal system is available in the Traffic Signal Guide(PDF, 273KB).

Will you adjust the signal timing during road construction projects?

With the use of the new Intelligent Transportation System devices, we will be better equipped to monitor and make any needed adjustments to the signal timing as street conditions change. Being able to control the signals from the Lincoln Transportation and Utilities Operations Center will make many different adjustments possible.

Why don’t all the pedestrian lights count down?

Walk, countdown, and flashing “Don't Walk” signals are installed depending on the width of intersections and number of pedestrians crossings. Installing those signals is data driven because they can impact traffic movement through an intersection. The countdown crosswalk signals typically stop traffic longer, which is not optimal for every intersection. Alternatively, by installing pedestrian pushbuttons, we can more efficiently give the green time to the majority of the traffic and still serve pedestrian crossing needs when they are present.

Are signals timed with other signals on intersecting corridors so a driver turning off one street does not immediately get stopped at a nearby red light on the other street?

It depends on the situation and traffic volumes. Most times we set coordination plans for the mainline or through movements on each street. When both streets are coordinated, turning onto a new street puts you in the non-coordinated portion of that street. You would typically get a red light at the next signal, but would then be back in coordination when it turns green. At certain locations where there are very high left- or right-turn volumes off a side street, we will time cross-street signals to account for that.

Are the detection cameras used for automated enforcement?

Automated enforcement is not allowed under Nebraska law and the cameras being employed for traffic detection do not have this capability. They can identify vehicles of various sizes and pedestrians, but do not monitor red lights or speeding. The cameras are also not regularly recorded, so the City cannot provide video as evidence when crashes occur.

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