DPS stands for "Department of Public Safety". DPS is usually a state law enforcement agency responsible for enforcing state and local laws or in other words; the police.
DPS is usually an umbrella term which can encompass, the state police (highway patrol), liquor control board, and gaming / lottery enforcement. This though varies greatly by state.
Here are some other names that state law enforcement agencies use:
Highway Patrol, State Troopers, or the State Police.
Current Police Officer