"Strategically deployed at stations throughout the system and involved in up to 1,000 train trips a month, the Amtrak Police Department K-9 teams provide a psychological and physical deterrent to potential threats from explosives. These teams are part of a collaborative interagency initiative that includes the Transportation Security Administration, federal and state Departments of Homeland Security, and state and local law enforcement agencies.

For explosives detection, the teams undergo an 11-week training program at either the Auburn University Canine Detection Training Center in Alabama or the Transportation Security Administration facility at Lackland Air Force Base in Texas, where dogs are trained in odor recognition. During that time, handlers are taught to recognize changes in their dog’s behavior as a response to “alerting” on a potential threat.

Part of the standard explosives detection training includes vapor wake training, where the dogs are trained to alert on scents left in the wake of a passing individual. Amtrak currently has the most K-9 units in the railroad industry with vapor wake capabilities." -

https://police.amtrak.com/units/special-operations/k-9-unit.html