英文關鍵字
area
arriving
automobile
business
cars
city
column
concept
control
convoy
crime
demonstration
destination
enforcement
guard
guarding
law
light
metropolis
monitor
observe
operation
order
patrol
people
police
policeforce
policeman
prevention
privacy
property
protection
public
revolution
road
row
safe
safety
security
space
spy
surveillance
system
terrorism
traffic
transport
transportation
urban
vehicle
warning