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Welcome

How Connected Signals Save Seconds—and Lives—in Phoenix

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HOW CONNECTED SIGNALS SAVE SECONDS—AND LIVES—IN PHOENIX

Nikhita Singh Satish

Systems Enginner

Yunex Traffic

Joe Marioni

Territory Manager

Western Systems

Donald Wang

Connected Vehicles

Network Expert

Western Systems

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Overview

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Reduced EMS Response Time – Benefits & Methodology

Study Area: Ahwatukee

Population: 85,000

Cardiac Arrests/Year: 78.5

Metric	Before CV	After CV
Response Time	5.22 min	4.75 min
Survival Probability	19.7%	21.6%

Avoided Deaths/Year: ~1.5

Value of Life Saved (VSL, 2024): $13.7M

EMS Annual Savings: ~$20.28M (20% considered)

Faster EMS response times = lives saved + millions in economic benefit.

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The data that they pulled has proven to be strongly recommended By CATS. Response time was reduced by 9%. . One thing is that the vehicle CATS was using did not have ER lights, so this number could be greater. This giving us 1.5 lives saved in a year. It increased survival probability roughly 2%. What I found staggering was the money, I had no idea a life and a half was worth 13.7 M , that’s a lot. I am going to have to bring this up to my boss during my yearly review. Another thing I want to point out is we didn’t test the vehicle to vehicle communication of the OBU. It turns out that when you have two Emergency Vehicles travelling at high speeds, in dynamic situations, going to the same location, they tend to hit each other a lot. According to the Captain at PFD, they are overwhelmed at the shop fixing these response vehicles. Less vehicles=less support on multiple calls.

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Technology Highlights

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Connected Vehicle Concept

Pedestrian Safety Messages (PSM)

Position
Speed
Heading

Basic Safety Messages (BSM)

Position
Speed
Heading
Status

CMS

RSU

Controller

Traveler Information Message (TIM)

Warning sign content
Location of the warning sign

Signal Phase and Timing (SPaT)

Current phase status
Time to phase change

MAP

Intersection geography
Lanes allowed to Maneuvers

Connected vehicle technology is at the forefront of transforming how we approach road safety, traffic management, and overall mobility. By utilizing sensors, cameras, and devices like Roadside Units (RSUs) and On-Board Units (OBUs), connected vehicle technology enables vehicles to connect with each other, infrastructure, and other road users like cyclists and pedestrians. For example, It can alert drivers to potential dangers such as a car running a red light or traffic conditions ahead, giving them more time to react and avoid accidents.

To be able to provide real time alerts the RSU gathers information of the traffic intersection through SPAT and MAP messages which give intersection geometry. The on board units or smartphone applications broadcast the current status of the cars and pedestrians.

And then we have central management system running in the cloud to monitor these devices remotely.

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Comparison of Roadside Unit Architectures

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RSU as “radio”

RSU as an edge computing unit

Controller with CV Module + RSU

Controller + Smart RSU

RSU vendor agnostic CV apps

All in one device for CV
Easy setup and integration
Cost-effective
Supports standalone RSU use cases: Work zones, pedestrian safety, wrong way detection

Clean security architecture: �RSU are enrolled in SCMS
Clear device certification

Controller is required 🡪 intersection use cases only
More complex interfaces (two vs one CV component)
Additional cost for CV module
Security architecture is unclear: CV Co-Processor does not have HSM

Controller Cabinet w/controller

CV Co-processor

Roadside Unit

Controller Cabinet w/controller

Roadside Unit

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When deploying Connected Vehicle technology, the architecture of the Roadside Unit (RSU) plays a critical role in determining scalability, cost, and ease of integration.�On the left, we see a more traditional setup.�When RSU just has radio capabilities , you need an additional Co-processor to run your applications. This poses a serious security risk as it brings an additional attack surface. They do not have an HSM or no defined security standards established like in the case of Road Side units.

In contrast, we have the roadside unit as an edge computing unit..

You have all you need for your CV solutions in one device. This how Yunex Rsus are built. And this makes it a very cost effective solution because you do not need an additional hardware hosting the Connected vehicle coprocessor to run your applications separately.

It has a clean security architecture. RSUs are enrolled using security credential management systems and certificates are used for verifying the messages being exchanged.�

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Emergency Vehicle Preemption

C-V2X

SRM 🡪

🡨 SSM

NTCIP 1202

🡪

🡨 SRM

SSM 🡪

C-V2X

🡨 SRM

SSM 🡪

C-V2X

All vehicles use the same C-V2X CH183 per latest FCC rules for transportation systems
Standardized SAE messages and security, nothing proprietary
All vehicles continually informed of priority status:

Green GRANTED to highest priority vehicle converging to the response site
Green DENIED to lower priority vehicles on conflicting approaches

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Lets look at how emergency vehicle preemption works.

Operation:

OBUs from all vehicles on approach transmit standard SRM with common security measures
RSU translate all SRMs into NTCIP 1202 Preemption to TSC
TSC is preconfigured to prioritize all requests per local policy
TSC responds with NTCIP Status to RSU of the active signal plan servicing the highest priority vehicle
RSU sends Signal Status Message (SSM) to all approaching OBUs containing the green phase served
Each OBU displays either 1) GRANTED if OBU is on GREEN approach or 2) DENIED if OBU is on a conflicting approach

The system is capable to manage conflicting requests by prioritizing by vehicle type.

This improves response times, reduces intersection conflicts, and enhances safety for all road users.

But the real value of this technology lies in its ability to scale.

By using standardized messaging and secure communication protocols, we can extend this capability beyond single jurisdictions.

This means emergency vehicles from different agencies — operating across city or county lines — can interact seamlessly with infrastructure, regardless of vendor or system differences.

Since the RSU, equipped with edge processing, can handle multiple requests in real time, prioritize them intelligently, and ensure safe signal adjustments — all without relying on external systems.

This level of interoperability is critical for coordinated response efforts, especially in complex or high-impact scenarios.

So while EVP is the starting point, the underlying architecture enables a much broader vision: scalable, secure, and interoperable V2I communication that supports a wide range of public safety and mobility applications.

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Mutual Response

C-V2X

SRM 🡪

🡨 SSM

NTCIP 1202

🡪

🡨 SRM

SSM 🡪

C-V2X

CAD/AVL Device

Priority Request 🡪

C-V2X

CAD / AVL

Schedule

Bus Locations

Backhaul

🡨 Conditional Priority

SRM 🡪

ID

Lane

ETA

Backhaul

Green until Passage

TSCs ahead on route

Route Map of Ingress & Egress Lanes

Peer-to Peer Priority Request 🡪

Transit Central

Central CAD / AVL System

On-Vehicle CAD / AVL Device

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The possibilities are endless.

Work Zone Warning

Pedestrian & Cyclist Proximity Warning

Virtual Queue Detection

Travel Time: Predicted & Measured

Exit Ramp Deceleration Warning

Curve Speed Warning

Signal Countdown Time to Change

Pedestrian Signal

Variable Speed Limit

Reversible Lanes / Closed Lanes

Emergency Vehicle Preemption

Green Light Optimal Speed Advice

Transit Signal Priority

Red Light Violation Warning

Wrong Way & Head On Crash Warning

Active Railroad Crossing Violation Warning

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Everything we’ve discussed — from emergency preemption to scalable, secure architectures — lays the foundation for a wide array of V2I applications.

On this slide, you’ll see examples like:

Transit Signal Priority

Work Zone Alerts

Pedestrian Safety Enhancements

Wrong-Way Driver Detection

Real-Time Safety Messaging

School Zone Speed Management

These aren’t just future concepts — they’re real, deployable solutions.

And with RSUs like ours, these applications are already built in and ready to activate. That means agencies can start small and expand over time, without needing to overhaul their infrastructure.

The RSU becomes more than a device — it’s a platform for innovation.

Finally, whether the goal is improving mobility, enhancing safety, or supporting coordinated emergency response, the possibilities truly are endless — and they’re closer than we think.

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Questions?

1. Q: How does a connected vehicle receive signal priority status at an intersection?

A: The RSU communicates with the vehicle’s onboard unit (OBU) via C-V2X, sending a “GRANTED” or “DENIED” response after evaluating priority policies configured in the traffic controller (typically via NTCIP 1202 or local rules).

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2. Q: What happens when multiple connected vehicles request priority at the same time?

A: The system evaluates requests using a hierarchy defined by the agency (e.g., emergency over transit, transit over freight). Only one request is granted per cycle. Others may be deferred or denied based on policy and phase compatibility.

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3. Q: How does the RSU distinguish between priority and non-priority vehicles?

A: Priority vehicles are equipped with OBUs that send authenticated Signal Request Messages (SRMs) containing metadata like vehicle class and ID. The RSU filters and forwards valid requests to the controller for processing.

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4. Q: How does a TSP-enabled corridor determine when to extend green time?

A: When the CAD/AVL system detects that a transit vehicle is behind schedule, it triggers the OBU to send an SRM. If the RSU validates the request, it communicates with the controller to apply green extension or phase holding, based on pre-set thresholds.