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Program Profile: Engine Immobilizers

Evidence Rating: Effective - One study Effective - One study

Date: This profile was posted on May 26, 2011

Program Summary

Devices that prevent a vehicle from starting unless they receive the correct signal from the driver. The goal of these systems is to reduce car theft. The program is rated Effective. Cars fitted with immobilizers reduced rates of theft compared with cars not fitted with the device.

Program Description

Program Goal

Engine immobilizers are devices that prevent a vehicle from starting unless they receive the correct signal from the driver. The goal of these systems is to reduce car theft.


Program Components

Engine immobilizer devices isolate the ignition system, the fuel system, the starter engine, or a combination of these systems. In order for a vehicle to start, the device must first receive a signal, which can be communicated in a number of ways:


  • Transponder (usually built into original keys)
  • Remote key (a handheld device that sends a radio or infrared signal)
  • Electronic key
  • Coded keypad
  • Key switch

Immobilizers penetrate car markets in different ways. For instance, in Australia, since 2001, it has been compulsory for all new vehicles to have an immobilizer device installed that meets the Australian Design Requirements (AS/NZS 4601:1999) that were issued in 1999. The Western Australian government also started subsidizing the aftermarket installation of such devices in 1997 and made such installations required in 1999.

Evaluation Outcomes

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Study 1

Vehicle Theft

Potter and Thomas (2001) found that engine immobilizers reduced the rate of vehicle theft. In most cases, cars fitted with immobilizers had reduced rates of theft compared with cars not fitted. Immobilizers that met more rigorous standards of security were found to be more effective in reducing thefts. For instance, of the 116,906 vehicles stolen in 2000, 91.2 percent had no immobilizer, 4.9 percent had an immobilizer that did not meet Australian Standards, and 3.9 percent had an immobilizer that met Australian Standards.


The lower rate of theft was demonstrated through multiple analyses looking at different kinds of cars, different kinds of immobilizers, and different jurisdictions.

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Evaluation Methodology

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Study 1
Potter and Thomas (2001) used a time series design with multiple experimental and comparison groups to compare the effectiveness of six main kinds of engine immobilizers used in Australia. The researchers used theft and registration data from across Australia. The analysis compares theft rates for each group of vehicles fitted with a particular kind of immobilizer with theft rates for remaining vehicles over time. The analysis only assumes the presence of an immobilizer device if it was standard for a vehicle model and thus does not account for any aftermarket installations. It includes some specific case studies of particular models, before and after these were fitted at manufacture with an immobilizer. It undertakes some interstate comparisons of immobilizer effectiveness and also includes a detailed study of the voluntary and compulsory fitting of immobilizers to vehicles in one state, Western Australia.

The total number of stolen vehicles for the study exceeds 100,000. Certain areas had data for up to 11 years. Generally, data was collected for 1990 through 2000.

The study did not address the cases where the trend of reduced theft preceded the installation, nor whether offenders moved from secure to nonsecure cars.
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There is no cost information available for this program.
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Evidence-Base (Studies Reviewed)

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These sources were used in the development of the program profile:

Study 1
Potter, R., and P. Thomas. 2001. Engine Immobilisers: How Effective Are They? Melbourne, Australia: National Motor Vehicle Theft Reduction Council.
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Program Snapshot

Geography: Suburban, Urban

Setting (Delivery): Other Community Setting

Program Type: Community Crime Prevention , Situational Crime Prevention, Specific deterrence

Current Program Status: Active

Paul Thomas
NATIONAL CARS Project, Attorney General's Department
GPO Box 464
Adelaide 5001
Phone: 61.8.8207.1669
Fax: 61.8.8207.2504