I don't know about tough on crime but the court systems typically are not tough on drunk drivers - especially those that kill someone. If an impaired driver gets four years for killing someone, that seems to be on the high side of sentences and then they're out within 1.5 - 2 years anyways. That seems woefully inadequate for taking a life or lives.
As for dropping crime rates, according to Stats Can, impaired driving rates are actually on the rise.
$1:
According to data from the Uniform Crime Reporting (UCR) survey, police reported 90,277 impaired driving incidents in Canada in 2011, about 3,000 more than in 2010 (Table 1). The rate of 262 incidents per 100,000 population was 2% higher than in 2010, the fourth increase in the last five years.
[url]www.statcan.gc.ca › Home › Publications › 85-002-X › Juristat › 2013 [/url]