Modified-Emergency Index (MEI): Advanced Criticality Metric for Autonomous Driving in Lateral Conflict

Overview

• This repository provides a codebase designed to evaluate real-time collision risks between two traffic participants based on their motion states and dimensions called MEI (Modified-Emergency Index), which is an advanced improvement of the Emergency Index (EI).
• First, the Separating Axis Theorem (SAT) is used to determine whether a collision has occurred. For pairs of participants that have not collided, the code calculates two key metrics: ACT and MEI, which quantify the real-time risk of collision.

Key Metrics

• MEI (Modified-Emergency Index):

  • Unit: [m/s]
  • MEI > 0 indicates that a collision is inevitable if the current motion states remain unchanged.
  • A higher MEI value signifies a higher collision risk.
  • The goal is to reduce MEI to a value less than 0 to resolve the conflict.

• ACT (Anticipated Collision Time):

  • Unit: [s]
  • ACT is a 2D extension of the Time-to-Collision (TTC) metric.
  • ACT > 0, with values closer to 0, indicates higher collision risk.

This repository also includes an open-source implementation of ACT calculations, specifically for scenarios where MEI > 0 is a prerequisite.

Library Requirements

This script requires the following Python libraries:

• numpy

Input Data Format

The code processes vehicle motion states using the following variables:

Variable	Description	Unit	Format
x_A	X-coordinate of ego vehicle (Vehicle A) centroid	m	float
y_A	Y-coordinate of ego vehicle (Vehicle A) centroid	m	float
v_A	Speed of ego vehicle (Vehicle A)	m/s	float
h_A	Heading angle of ego vehicle (Vehicle A)	rad	float, range [-π, π], e.g., 1.57 represents 90°
l_A	Length of ego vehicle (Vehicle A)	m	float
w_A	Width of ego vehicle (Vehicle A)	m	float
x_B	X-coordinate of surrounding vehicle (Vehicle B) centroid	m	float
y_B	Y-coordinate of surrounding vehicle (Vehicle B) centroid	m	float
v_B	Speed of surrounding vehicle (Vehicle B)	m/s	float
h_B	Heading angle of surrounding vehicle (Vehicle B)	rad	float, range [-π, π], e.g., 1.57 represents 90°
l_B	Length of surrounding vehicle (Vehicle B)	m	float
w_B	Width of surrounding vehicle (Vehicle B)	m	float

Future Work

• More experiment-related code will be made public in the future. Stay tuned!