Most drunken-driving programs focus on driving. This one worked because it focused on booze.

Many offenders in the program had served extensive time in jail and prison, so why were they deterred by the prospect of a single night in jail?  Midgette emphasizes the typical time horizon of the population, noting that “because heavy drinkers tend to heavily discount the future, deterrence depends much more on the certainty and swiftness of a sanction than its severity.”

In short, the possibility of a long prison term at some distant point—such as a sentence a repeatedly intoxicated driver might face if he eventually kills someone in an accident—does not deter drinking, but a single night in jail does if there’s a 100 percent chance the offender will face it immediately.