Making intersections safer with I2V communication

Abstract: Intersections are hazardous places. Threats arise from interactions among pedestrians, bicycles and vehicles, more complicated vehicle trajectories in the absence of lane markings, phases that prevent determining who has the right of way, invisible vehicle approaches, vehicle obstructions, and illegal movements. These challenges are not fully addressed by the "road diet" and road redesign prescribed in Vision Zero plans, nor will they be completely overcome by autonomous vehicles with their many sensors and tireless attention to surroundings. Accidents can also occur because drivers, cyclists and pedestrians do not have the information they need to avoid wrong decisions. In these cases, the missing information can be computed and broadcast by an intelligent intersection. The information gives the current full signal phase, an estimate of the time when the phase will change, and the occupancy of the blind spots of the driver or autonomous vehicle. The paper develops a design of the intelligent intersection, motivated by the analysis of an accident at an intersection in Tempe, AZ, between an automated Uber Volvo and a manual Honda CRV and culminates in a proposal for an intelligent intersection infrastructure. The intelligent intersection also serves as a software-enabled version of the `protected intersection' design to improve the passage of cyclists and pedestrians through an intersection.

• The paper demonstrates an I2V system that delivers real-time signal phase and timing data to reduce intersection hazards.
• It details a four-step approach including guideway construction, conflict zone detection, and blind zone sensor integration.
• Results suggest a cost-effective strategy (approximately $25K-$50K) to enhance safety and traffic flow at high-risk intersections.

Making Intersections Safer with I2V Communication

Introduction

Intersections for urban road users are fraught with hazards, due to the complex interactions among vehicles, bicycles, and pedestrians. The paper "Making intersections safer with I2V communication" (1803.00471) presents an innovative solution to address these challenges through intelligent infrastructure. By leveraging Infrastructure-to-Vehicle (I2V) communication, this approach provides critical real-time information to mitigate risks, thereby enhancing safety without the need for physical redesigns.

Intersections as Hazard Zones

Intersections lack lane markers, leading to conflict zones where trajectories intersect, increasing crash likelihood. Vision Zero (VZ) plans have attempted to improve safety by modifying intersections to enforce speed limits and lane reductions, aiming to protect pedestrians and cyclists. Despite such efforts, accidents persist due to incomplete phase information, temporal uncertainty, and blind spots. Autonomous vehicles (AVs), although poised to reduce human error-related crashes, struggle with intersection complexity as demonstrated by a significant proportion of AV crashes occurring near intersections [CADMV_Acc].

Figure 1: Safety issues encountered by AVs at intersections and the observational insights from crash scenarios.

Figure 2: Common intersection conflict scenarios.

A Case Study: Accident Analysis

The paper analyzes an accident involving an automated Uber Volvo and a manual Honda CRV. The collision was attributed to insufficient communication regarding signal phases, blind spots caused by adjacent stationary vehicles, and misjudgments on occupancy predictions. These errors exemplify typical dilemmas faced at intersections, necessitating advanced I2V communication systems to furnish missing information.

Figure 2: Analysis of the intersection accident between a Honda CRV and an Uber Volvo.

Figure 1: Collision scenario at a Tempe intersection involving automated Uber Volvo.

I2V Communication System Design

The paper proposes a four-step method to deploy I2V systems for enhancing intersection safety:

1. Guideway Construction: Define trajectories and permissible movements, grouping them into guideways based on potential interactions.
2. Conflict Zone Identification: Detect zones where guideways intersect, establishing potential points of collision.
3. Conflict Resolution: Utilize signal lights and SPaT (Signal Phase and Timing) messages to differentiate permissible from conflicting movements, thereby minimizing judgment errors.
4. Blind Zone Detection: Deploy sensors to ascertain occupancy within obscured regions, transmitting alerts to prevent unexpected intrusions.

Figure 3: Illustration of the approach to constructing guideways and conflict zones.

Figure 3: Trajectories and conflict zones impacting the safe execution of vehicle movements.

Intelligent Intersection

An intelligent intersection extends the infrastructure's capability, broadcasting comprehensive SPaT messages alongside blind zone occupancy alerts for AVs and connected vehicles. Red-light violator detection can further secure the intersection environment. The paper highlights the cost-effectiveness of such systems, estimating upgrades at \$25K-\$50K, while arguing for prioritizing high-risk intersections based on traffic analyses.

Figure 4: Enhanced intersection designs including protected features and intelligent systems.

Figure 5: Schematic of a protected intersection design.

Implications and Future Directions

Intelligent intersections offer essential improvements over physical modification and isolated AV systems. By providing real-time spatial and temporal data, these systems augment vehicle decision-making processes, potentially reducing collision risk and improving traffic flow without sacrificing mobility. The paper suggests continued research to optimize intersection designs with intelligent systems, advocating for integrated approaches that combine VZ and I2V principles to achieve safer urban environments.

Conclusion

The paper argues powerfully for the integration of infrastructure intelligence as a pivotal strategy for enhancing intersection safety. By employing I2V communication to deliver critical phase, timing, and blind zone data, intersections can become significantly less hazardous spots for AVs, cyclists, and pedestrians alike. This approach not only complements existing safety measures but also promises an enduring and adaptable solution to intersection challenges.

Overall, "Making intersections safer with I2V communication" contributes significantly to the dialogue on urban traffic safety, inspiring further exploration and deployment of intelligent transportation systems.