Train Accidents Glossary

• Alternative Safety Measure (ASM)
• Engineering Alternative Safety Measures (ASMs)
• Four-Quadrant Gate
• Intermediate Quiet Zone
• Modified Supplementary Safety Measure (SSM)
• MUTCD
• Nationwide Significant Risk Threshold (NSRT)
• Non-engineering Alternative Safety Measure (ASM)
• Partial Quiet Zones
• Quiet Zone
• Quiet Zone Risk Index
• Relevant Collision
• Risk Index
• Risk Index With Horns (RIWH)
• Supplementary Safety Measure (SSM)
• Wayside Horn
• Whistle ban or Pre-Rule Quiet Zone