The Station Square Police Department is a group that appears in Sonic Adventure and Sonic Adventure DX: Director's Cut. It is the main defense force of Station Square. However, they are ill-equipped to tackle monsters, such as Chaos.
In Sonic Adventure, SSPD officers were deployed to intercept Chaos. They arrived at the scene, taking positions. Their commander ordered them to fire, but their weapons proved useless against Chaos. The commander then ordered all personnel to retreat, while giving cover fire. Luckily, Sonic arrived and disposed of Chaos. They later appear at several points in the story, causing roadblocks or ceasing access to the train station.