Mandatory course in driving on slippery roads for drivers of heavy vehicles. Effect on the accident risk

The effect of a course in driving on slippery roads for drivers of heavy vehicles was studied by three methods: A comparison of drivers with and without the course, a comparison of the risk on slippery roads and on dry roads for drivers with and without a course and a logistic regression with the involvement in accidents as the dependent variable and having gone through a course or not as one of the independent variables. By the first method a significant increase in accident risk was found for drivers that had gone through the course. The other two methods indicated an increase as well, but in these cases the increase was not statistically significant. It is therefore uncertain whether the accident risk is increased by the course, but a conclusion of no reduction is uncontentious.