10 Best Safety Interlock systems for your vehicle

Vehicle safety interlock systems are designed to ensure that specific safety conditions are met before allowing certain operations (e.g., starting the engine, shifting gears, or opening doors). They help prevent accidents, encourage safe driving behavior, and protect occupants.

1. Brake-Shift Interlock System

Function: Prevents the gear shifter from being moved out of “Park” unless the brake pedal is pressed.
Purpose: Avoids unintentional movement of the vehicle.
Common In: Almost all modern automatic transmission vehicles.
Example Use Case: Prevents a child from accidentally shifting the car into “Drive.”

2. Seat Belt Interlock System

Function: Prevents the engine from starting or shifting into gear unless the driver’s seat belt is fastened.
Purpose: Forces the driver to wear a seat belt before operation.
Common In: Some fleet vehicles, commercial trucks, or experimental safety programs.
Note: Was mandated briefly in the U.S. in the 1970s but removed due to public resistance.

3. Door Interlock System

Function: Prevents the vehicle from moving (or gear from engaging) if any door is open.
Purpose: Ensures passenger safety, especially in vans, buses, and school vehicles.
Common In: Buses, industrial vehicles, and some high-end passenger vehicles.
Example Use Case: A bus won’t move if a side door is open.

4. Clutch Interlock System

Function: In manual transmission vehicles, prevents the engine from starting unless the clutch pedal is fully depressed.
Purpose: Avoids sudden forward lurching when starting the engine in gear.
Common In: Manual cars, motorcycles, and heavy equipment.

5. Neutral Safety Switch

Function: Prevents the engine from starting unless the transmission is in “Park” or “Neutral.”
Purpose: Prevents accidents caused by starting the engine in gear.
Common In: Automatic transmission vehicles.

6. Ignition Interlock Device (Alcohol-related)

Function: Requires a breath sample with no or low alcohol content before allowing the vehicle to start.
Purpose: Prevents drunk driving.
Common In: Mandated for DUI/DWI offenders.
Advanced Features: Some have cameras, GPS, and real-time reporting.

7. Parking Brake Interlock

Function: Prevents shifting out of “Park” unless the parking brake is disengaged, or vice versa.
Purpose: Ensures vehicle is secure when parked, especially on inclines.
Common In: Heavy vehicles, buses, and commercial trucks.

8. Safety Belt Reminder System (Semi-Interlock)

Function: Provides visual and audible warnings if seat belts are unfastened.
Purpose: Encourages seat belt use but doesn’t prevent vehicle operation.
Common In: All modern cars (mandatory in many countries).
Note: Not a full interlock, but considered part of the safety system family.

9. Reverse Gear Interlock

Function: Prevents the vehicle from shifting into reverse while moving forward at speed.
Purpose: Protects transmission and prevents accidents.
Common In: Automatic and CVT transmissions.

10. Child Safety Door Lock Interlock

Function: Prevents rear doors from being opened from the inside.
Purpose: Keeps children from accidentally opening doors while driving.
Common In: All modern family cars.

🔄 Summary Table

Watch Lifesaver interlock systems.

Interlock Type	Trigger Condition	Operation Blocked	Used In
Brake-Shift	Brake not pressed	Gear shift	Automatics
Seat Belt	Seat belt not fastened	Engine start or gear shift	Fleets, school buses, some cars
Door Interlock	Door open	Vehicle movement	Buses, vans, EVs
Clutch Interlock	Clutch not pressed	Engine start	Manual vehicles
Neutral Safety Switch	Not in Park/Neutral	Engine start	Automatics
Alcohol Ignition Interlock	Alcohol detected	Engine start	DUI offender vehicles
Parking Brake Interlock	Parking brake not engaged/disengaged	Gear shift or movement	Trucks, buses
Seat Belt Reminder	Seat belt not fastened	— (only warning)	All modern vehicles
Reverse Gear Interlock	High forward speed	Reverse gear	Modern transmissions
Child Door Lock Interlock	Child lock activated	Door opening from inside	Rear doors in family cars