Vehicle-to-Infrastructure (V2I)

Vehicle-to-Infrastructure (V2I) communication is one of the pivotal communication modes within the Vehicle-to-Everything (V2X) ecosystem. It facilitates real-time, bidirectional wireless data transmission between vehicles and roadside infrastructure (such as traffic lights, roadside perception sensors, electronic signboards, toll plazas, and Roadside Units [RSUs]). While standalone onboard intelligence gives a vehicle the "eyes" to observe its immediate surroundings, V2I provides "beyond-line-of-sight vision", enabling vehicles to anticipate traffic conditions well ahead—serving as a foundational technology for intelligent transport systems (ITS) and advanced autonomous driving.

Technical Principles

The V2I system operates on a continuous closed-loop cycle of "broadcast-receive-compute". Its standard architecture comprises Roadside Units (RSUs), On-Board Units (OBUs), communication networks, and cloud platforms.

Roadside Perception and Broadcasting: RSUs installed at junctions interface with cameras, millimetre-wave radars, LiDAR sensors, and traffic light controllers to continuously gather real-time data on traffic flow, signal phases, and road hazards. Utilising low-latency communication protocols such as C-V2X or DSRC, the RSU broadcasts data packets—including Signal Phase and Timing (SPaT) and road hazard alerts—at high frequencies of dozens of times per second to vehicles within a 300 to 1,000-metre radius.

Vehicle-End Reception and Response: Once the vehicle's OBU receives the broadcast from the RSU, the onboard domain controller processes the data in milliseconds. Even when visual blind spots exist (such as traffic lights obscured by heavy vehicles), the system provides advance alerts to the driver, including "Green Light Optimal Speed Advisory (GLOSA)", "Red Light Violation Warning (RLVW)", or "Roadworks Ahead". Certain models can even interface directly with autonomous driving systems to initiate automated deceleration or evasive manoeuvres.

V2I communication primarily relies on two technological pathways: Cellular Vehicle-to-Everything (C-V2X) and Dedicated Short-Range Communications (DSRC). With ultra-low latency (as low as 3–10 ms), wide coverage, and continuous evolution capabilities, C-V2X (particularly 5G V2X) has emerged as the global mainstream standard. Meanwhile, DSRC, based on the IEEE 802.11p standard, remains widely deployed across earlier pilot projects.

Core Functions and Application Scenarios

V2I forms the bedrock for numerous advanced smart mobility features, spanning safety, efficiency, and cooperative driving:

• Improving Traffic Flow Efficiency: With the "Green Light Optimal Speed Advisory" function, the RSU transmits traffic light countdown data to the vehicle. The system then calculates an optimal driving speed to help the driver clear junctions during green light windows, effectively reducing stop-and-go delays and cutting fuel consumption by approximately 10%.

• Enhancing Driving Safety: This represents the core value of V2I. By leveraging roadside perception, vehicles can detect hazards beyond their own sensor limits, enabling features such as Red Light Violation Warning (RLVW), road hazard alerts (e.g., slippery surfaces, obstacles), and Vulnerable Road User (VRU) alerts.

• Enabling Cooperative Autonomous Driving: In scenarios such as "cooperative highway ramp merging" and "cooperative junction management", RSUs generate optimised coordination strategies based on macro traffic data to assist vehicles in navigating intersections safely and seamlessly. For instance, at unsignalised junctions, the system actively prevents collisions caused by blind spots.

Industry Landscape and Challenges

V2I is rapidly shifting from pilot trials to full-scale commercial deployment. The global V2I market was valued at approximately USD 47.36 billion in 2025 and is projected to reach USD 247.07 billion by 2035, charting a compound annual growth rate (CAGR) of 17.97%.

Strong Regulatory and Policy Backing: Major automotive markets including the European Union, the United States, and China are actively mandating V2X integration through legislation and NCAP safety assessment roadmaps. China's "Vehicle-Road-Cloud Integration" strategy is progressing swiftly, with 20 pilot cities—including Beijing, Shanghai, and Wuxi—undertaking extensive roadside infrastructure rollouts; Wuxi alone has upgraded traffic lights across more than 1,700 junctions.

Ongoing Challenges: Broad-scale V2I deployment continues to face key hurdles, including high infrastructure capital expenditure, data security and privacy compliance, and cross-vendor multi-device interoperability.

Important Note: In its current phase, V2I primarily functions as an "extended sensor" and an "early warning system". While it serves as a vital complement to standalone vehicle perception, it cannot completely substitute a vehicle's primary onboard sensors. Drivers must not rely solely on V2I to the detriment of observing physical road signs, road markings, and real-time traffic conditions, and remain ultimately responsible for vehicle operation and safety.