Science Daily reports on research that found, for high risk individuals, the greatest deterrent to driving while intoxicated is the perception - not the actual likelihood - of getting caught...

"Essentially, law enforcement needs to focus on perceptions; it is important that drivers perceive that they will be caught if they drive impaired," said Lilliard Richardson, professor in the MU Truman School of Public Affairs. "We found that high-risk drivers are less likely to drink and drive if they perceive they are likely to be stopped or arrested by police. However, the mere existence of laws designed to discourage people from drinking and driving does not impact high-risk drivers. The results provide support for the value of high-visibility enforcement campaigns. Public safety education and media efforts are important components of the overall strategy for reducing impaired driving."

This suggests the importance of education and awareness efforts that target the higher-risk groups with information about the investigation and prosecution of those who inflict injuries.