Green Light Lincoln

“Green Light Lincoln” is an initiative by the City of Lincoln Traffic Engineering Division to improve traffic safety and traffic flow citywide. Motorists in every corner of the community will see reduced congestion and ease of travel due to prioritization and implementation of several key components of the Traffic Management Master Plan.

Green Light Lincoln - It's GO Time

The continued deployment of Green Light Lincoln will result in vast improvements to the overall traffic signal system, and numerous projects with high benefit/cost ratios. 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

In order to make signal equipment and signal timing upgrades at the 410-plus signals across the City, implementation will occur through multiple phases. Phases 1, 2 and 3 are complete. Phase 4 will be completed in 2020.

Upgrades

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.

For the past five years, 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.

New Signal Displays and Signal Phasing Alternatives

The City is reevaluating the use and installation of protected left-turn movements (solid green left-turn arrows), and when those movements will be served to better accommodate flow for oncoming traffic. Cycle lengths (the time from the start of green on your street until your green starts again) will be evaluated to better clear the left-turn movements. Flashing Yellow Arrows, which are becoming the new nationwide standard, will be used more frequently.

Intelligent Transportation Systems (ITS) Deployment

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 is installing 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 Operation Center to better administer this new technology and provide quicker and more efficient responses to various incidents and events throughout the city.

Results to Date

Green Light Lincoln includes traffic signal equipment and signal timing upgrades. Annual benefits resulting from signal timing and equipment upgrades to date include the following performance measures:

61.4 million vehicle stops 840,000 hours of delay 1.1 million gallons of fuel $17.6 million dollars 11,000 kilograms of emissions

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

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 $22.3 million.

The resulting benefit-to-cost ratio is 18:1

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

Final Reports

Phase 4

At the conclusion of 2020, Phase 4 will complete the “first round” of Green Light Lincoln, addressing all remaining intersections that were not included in any of the first three phases. Equipment upgrades will include standardizing signal displays, incorporating flashing yellow arrows where applicable, and upgrading traffic signal cabinets to accommodate current and future technology upgrades. Improvements can be expected at 69 locations as part of Phase 4.

Frequently Asked Questions

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When did this project start?

Green Light Lincoln kicked off January 1, 2016. Implementation of Phases 1, 2 and 3 is complete and Phase 4 will be completed in 2020.

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 are we changing 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 new 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.