Transportation
- Sensitive Security Information, a designation used by the United States Transportation Security Administration (49 CFR part 1520) and the Department of Transportation (49 CFR part 15)
- Solid State Interlocking is the brand name of the first generation processor-based interlocking developed in the 1980s by British Rail, GEC-General Signal and Westinghouse Signals Ltd in the UK
Read more about this topic: SSI