AACN: Advanced Automatic Crash Notification
AASHTO: American Association of State Highway and Transportation Officials
ABS: Anti-Lock Braking System
ACE: Automated Commercial Environment
ACL: Access Control List
ADA: Americans with Disabilities Act
ADMS: Archived Data Management Subsystem (legacy National ITS Architecture)
ADS: Archived Data System
ADUS: Archived Data User Service
AERIS: Applications for the Environment: Real-Time Information Synthesis
AFD: Architecture Flow Diagram
AHM: Ad Hoc Messages
AHS: Automated Highway System
AID: Architecture Interconnect Diagram
ALB: Anti-Lock Brakes
ANSI: American National Standards Institute
APDU: Application Protocol Data Unit
API: Application Programming Interface
APTA: American Public Transportation Association
APTS: Advanced Public Transportation System
ARC-IT: Architecture Reference for Cooperative and Intelligent Transportation
ASD: Aftermarket Safety Device
ASTM: American Society for Testing and Materials
ATC: Automatic Train Control
ATC: Advanced Transportation Controller
ATIS: Advanced Traveler Information System
ATM: Asynchronous Transfer Mode
ATM: Active Traffic Management
ATMS: Advanced Traffic Management System
ATS: Automatic Train Stop
AVCS: Advanced Vehicle Control System
AVI: Automated Vehicle Identification
AVL: Automated Vehicle Location
AVO: Automated Vehicle Operation