Who Knew? GM Invented the DUI Ignition Interlock in 1970.

Everyone in 1970 was aware that drunk driving was a serious problem, but no one knew what to do about it.

Meanwhile, car safety was improving. Just a few years after losing the mandatory seat belt battle, the Big Four awoke to the idea that there was value in being seen as pro-safety.  In 1970 General Motors developed (but never marketed, to our knowledge) a kind of prototype of today’s ignition interlock. The device required a driver to reproduce a series of numbers that flashed on a screen by punching corresponding buttons. If they failed the test, the car wouldn’t start.

Why didn’t GM’s device take off?

If this device could really keep drunk drivers off the road, why does nothing remain of it, apart from a press photo? Most likely the federal government didn’t push GM’s discovery, and car companies generally didn’t push safety devices unless compelled to. It was legislation that made seat belts, head restraints, crashworthiness standards, and center brake lights universal.

Mostly, though, GM’s device failed because the idea was bad. The designers didn’t really understand how impaired drivers operate. Certainly it takes concentration to repeat the number sequence, but that isn’t enough to prevent a determined drunk to get on the road, for two reasons:

  • Many people over the .08 blood alcohol limit can force themselves to concentrate for the few seconds it takes to complete the test.   An impaired driver might get it together long enough to punch out the five numbers, they couldn’t stay alert long enough to drive safely.
  • A driver could start the car while sober and then begin drinking afterwards. Or a sober passenger could take the test in place of the driver (notice that in the photo the demonstrator is in the passenger seat). Back in 1970, when drunk driving didn’t have anywhere near the stigma that it does today, getting a friend to do “curb service” would be easy. Does that sound stupid? Remember, these people wore plaid pants and platform shoes.

What worked: the ignition interlock

A better technology made GM’s dream come true a few years later. In the 1980s California started a pilot program for devices which used breath alcohol ignition interlock (BAIID) technology. The new devices measured actual intoxication, rather than physical coordination, which made more sense and worked more efficiently.

Apart from keeping a drunk from starting the car, ignition interlocks also keep a sober driver from getting drunk after starting the car, because of something called a rolling re-test. The driver must breathe into the device periodically while driving, to ensure that he or she is still sober. Interlocks these days can be equipped with cameras as well, to ensure that the one taking the test is the driver. Images and data are downloaded and reviewed by monitoring authorities to ensure that the offender is complying with the interlock regulations. You could never require someone to re-punch numbers while driving: that’s the Achilles’ heel of the GM device.