I think so. I'm realizing the article is actually very confusing.

https://katu.com/news/local/speeding-in-portland-some-of-the-city-traffic-lights-are-designed-to-stop-you-speed-rest-red-light

Since 2024, the Portland Bureau of Transportation (PBOT) has used “Rest in Red” technology along Powell Boulevard between Southeast 21st and 33rd avenues. The system uses sensors to detect approaching vehicles. Drivers traveling at or below the speed limit receive a green light, while speeding drivers face a red light.

The system operates only at night.

https://www.portland.gov/transportation/vision-zero/rest-red#toc-rest-in-red-explained

Traffic signals with “rest in red” technology can display red lights in all directions during late night and early morning hours when traffic volume is light rather than cycling through green, yellow, and red the way they do normally during the day.

When a person driving a vehicle approaches a “rest in red” intersection, the traffic signal may stay red until it detects that the driver reached the intersection. Assuming no cross-traffic is approaching, the traffic signal will turn green to benefit people that are driving within the speed limit.

Other traffic signal technology examples

PBOT uses other types of traffic signal technology to encourage safe travel speeds. For example, if a person drives 13.5 mph downtown, they are more likely to catch green lights and travel in groups with other vehicle traffic.

Similarly, PBOT has deployed special signal timing along N Vancouver Avenue so people biking don’t repeatedly get stopped by red lights.

How the technology works

Detection

At most traffic signals, PBOT uses smart sensors to detect approaching cars to determine when to give a green light. PBOT currently uses "microwave detection" mounted on traffic signal mast arms. "Microwave detection" can locate approaching traffic from several hundred feet away.

Signal controllers

Signal controllers are the "brains" of the traffic signal that make "rest in red" work. During peak hours, signal controllers collect and communicate important information. During off-peak hours, signal controllers with the right detection can allow for different types of operation to minimize speeding.

Newer traffic signals are more likely to include smart detection technology and upgraded signal controllers. However, many traffic signals across the city are aging out and have limited or no detection as well as signal controllers which haven’t been upgraded.

PBOT plans to update traffic signals as needed and funding becomes available to match city policy.

Still confusing, but I think they're implementing both, over time.
Supposedly Oregn State University is or will be conducting research on its effectiveness in reducing crashss, but I couldn't find any info from them. Maybe that will clear things up.

It's hard to do correctly in a lot of cases. At least to the point where people going 10mph over don't go a further 10mph more. Although in most cases it's just idiots at city traffic management who can't do math.