Mass transit systems are designed to be open and accessible, and are intended to move large numbers of people rapidly and efficiently. Transit systems in larger cities have large numbers of stations with multiple entrances and exits, as well as multiple train platforms. All of these characteristics are a challenge to security, and TSA is actively pursuing programs and technologies to address those challenges.
Canine units are one of the approaches TSA is pursuing. We have created and deployed mobile canine units to allow for more targeted screening of passengers in the mass transit arena. Currently, there are 35 canine teams working in 11 mass transit systems. Their responsibilities include screening unattended items, searching subway and light rail cars and buses, and providing public visibility in the terminal and platform areas.