Requirement: The software recognizes the use of assistive technologies and adapts its user interface to improve accessibility. This includes at least the following:

• providing alt text for images,
• ensuring keyboard navigability,
• offering voice navigation, and
• maintaining high contrast for users with visual impairments.

Metrics:

• Screen Reader Efficiency: 95% of the content must be accurately read out by screen readers without user confusion over navigation or actions.
• Keyboard Navigability: All interactive elements must be accessible with a keyboard alone, and users should be able to complete all forms and transactions using keyboard shortcuts, aiming for task completion within 120% of the time taken using a mouse.
• Contrast Ratio: The website must maintain a minimum contrast ratio of 7:1 for normal text and 4.5:1 for large text.
• Error Rate: The error rate for users utilizing assistive technologies should not exceed 5% higher than for users not using these technologies, ensuring comparable ease of use.

This requirement has been crafted with help from ChatGPT 4.0.