• Layer One: Common Sense
• Layer Two: Visible or Audible Deterrent
• Layer Three: Vehicle Immobilizer
• Layer Four: Tracking System

Layer One: Common Sense

You should always secure your vehicle, even if you're parking for "just a minute." You should:

• Park in a well-lit area
• Remove your keys from the ignition
• Lock all of your doors
• Close all of your windows

Layer Two: Visible or Audible Deterrent

The second layer of protection is a visible or audible device that alerts thieves that your vehicle is protected. Popular second-layer devices include:

• Audible alarms—typically equipped with motion or impact sensors that trigger a 120-decibel siren
• Steering wheel locks—metal bars designed to prevent the steering wheel from turning
• Steering column collars—prevent thieves from hot-wiring the vehicle (some collars are installed permanently; others must be continuously activated.)
• Theft deterrent decals—visually warn thieves the vehicle is protected by an alarm or other anti-theft device
• Tire locks—similar to the circular steel boots used by many police departments, tire locks prevent the vehicle from being driven
• Window etching—if the vehicle identification number (VIN) is etched onto the vehicle's windows, it makes it difficult for thieves to resell the vehicle or its parts

Layer Three: Vehicle Immobilizer

The third layer of protection is a device that prevents thieves from bypassing your ignition and hot-wiring the vehicle. Some electronic devices have computer chips in ignition keys. Other devices inhibit the flow of electricity or fuel to the engine until a hidden switch or button is activated. Popular third-level devices include:

• Smart keys—contain specially-coded computer chips or radio frequencies (Without the exact key, the vehicle's engine cannot be started.)
• Fuse cut-offs
• Kill switches—inhibit the flow of electricity or fuel to the engine until a hidden switch is activated
• Starter, ignition, and fuel disablers