Centennial’s ‘intelligent’ stoplight timing system to expand

More roads will use technology to adapt lights to traffic conditions


With so many major streets running through Centennial, traffic has remained a top concern for the city, and a project to better adjust traffic lights will soon come to more of the city’s large roadways.

An early phase in the project — carried out on Yosemite Street — reached completion in October 2020, and the adaptive traffic-light system is set to expand in 2022 to other major corridors in the city.

Here’s a rundown of how Centennial’s “Intelligent Transportation System” works and where changes are coming soon.

Adding technology

“Intelligent Transportation Systems” is a blanket term that refers to technologies that can help address transportation issues, according to Anna Bunce, the city’s traffic engineer.

“ITS devices and applications can include many different things,” such as real-time adaptive traffic signal changes along with cameras for monitoring traffic conditions, Bunce said.

The cities of Centennial, Greenwood Village and Lone Tree collaborated in the past few years on a pilot project to reduce traffic congestion in the area.

The cities partnered on Yosemite Street between Lincoln and Belleview avenues to install sensors that enable the timing of traffic signals to be adjusted “in real time” as traffic patterns and volumes change throughout the day, according to the city’s website.

Adaptive traffic signal operations became active within Centennial on the Yosemite Street corridor in late 2020, according to Kelly Ohaver, a Centennial city spokesperson.

Spreading the idea

Centennial plans to expand the adaptive signal system to the Arapahoe Road and Dry Creek Road corridors west of Interstate 25, eventually adding the technology to other major roads east of I-25, such as Smoky Hill and Jordan roads and Himalaya Street, according to the city’s website.

The adaptive technology could be fully deployed on those corridors within Centennial at traffic signals owned and operated by the city in mid- to late 2022, according to Ohaver.

Because of Centennial’s snaking city boundaries, it can sometimes be confusing to identify when a location is or isn’t in Centennial. Arapahoe Road touches different municipalities as it spans through Centennial, and Arapahoe between I-25 and Parker Road is part of a state highway.

“We are, however, actively working on cross-jurisdictional coordination with multiple other adjacent jurisdictions to be able to share information regarding traffic signals and other ITS devices,” a statement from Ohaver said.

How it works

Different types of sensors each have their own methodologies for measuring travel time between sensor locations, but “most typically use various types of anonymized data from electronic devices to identify when a vehicle passes by multiple sensor locations,” the statement from Ohaver said.

“No one is watching or tracking a specific vehicle, driver or passenger,” the statement added.                       

Before the arrival of adaptive traffic signal technology, certain traffic signals operated with time-based programming, as is the case for most major corridors, according to the statement.

Under the old method, “different timing plans would be active for different times of day and different days of the week, which can be very effective for managing typical recurring traffic congestion such as that experienced during rush hours,” the city’s statement said.

Adaptive technology won’t always bring a large shift in traffic quality, but there are times when it’s especially effective, the statement continued.

“Adaptive traffic signal operations will not always produce dramatic improvements over a well-managed, regularly-retimed corridor during those regular recurring congestion events but can be much more effective when it comes to applying different timing parameters to unexpected changes in condition like a highway incident that pushes more traffic onto surface streets,” the statement said. 

Other components

Back in 2016, the city had no existing closed-circuit television cameras, according to Centennial’s 2016 Intelligent Transportation System Master Plan. As of 2019, the city had 62 intersections at which closed-circuit TV cameras are operational, according to city staff. The cameras are separate from the adaptive timing project, according to the city’s statement.

“Centennial does have a majority of signalized intersections equipped with pan-tilt-zoom (PTZ) cameras. These cameras are typically used to investigate traffic signal timing and operational concerns reported by constituents prior to dispatching field staff for additional troubleshooting,” the city statement said.

The cameras “may also support (city) staff in reporting incidents to emergency services that are impacting traffic so that they can be cleared in a more timely fashion,” the statement said.  

“Video from these cameras is not recorded or stored,” the statement added.

“Intelligent Transportation Systems” devices can also include weather stations, according to Bunce. As of the 2016 plan, road weather stations were operating within the city at four intersections.

The stations collect various data: air temperature, relative humidity, road surface temperature and condition — such as dry, wet or ice — and wind speed, according to the plan.

At that time, road weather stations were operating at the following intersections: Jordan Road and Fremont Drive, Arapahoe Road and Vine Street, Quebec Street and Costilla Avenue, and County Line Road and Chester Street. The hardware, which is owned by the city, is mounted on traffic signal poles, according to the plan.

“Additional weather stations and data (e.g., visibility, which is not currently provided) could be used to support automatic selection of weather-related timing plans,” the plan says. “The additional information could also be used to plan and manage snow-removal operations.”

Centennial Colorado, Intelligent Transportation System, traffic signals, lights, timing, Ellis Arnold


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