An Analysis of OWI Arrests and Convictions in Iowa, 2011

The primary goal of the project was to document the demographic profile of OWI offenders in Iowa. The study is based on both aggregate and case-level data. The case level data produced a final sample of 118,675 OWI convictions. That occurred from 2000 through 2009. The great majority of convicted offenders were White males. From 2000 through 2009 the percentage of convictions received by women increased by 34%. Defendants’ average age of was 30 years old, and the age cohorts of 15 to 24, 25 to 34, and 34 to 45 were overrepresented among convicted offenders. Whites were underrepresented among OWI defendants. African Americans, Hispanics and Native Americans were overrepresented. From 2000 through 2009, the percentage of aggravated misdemeanor felony OWI convictions received by Hispanics and African Americans increased significantly. The percentage of OWI convictions received by women and African Americans increased significantly after implementation of the .08 BAC law. We did not find convincing evidence of a direct relationship between enforcement trends and the alcohol related traffic fatalities (ARTFs). However, the ten year Iowa conviction trends did provide evidence of a conviction lag effect on Iowa’s ARTFs. The research findings established the basis for a phase two project that would assess the efficacy of OWI sentencing practices in Iowa.

Gradation Analysis of Cold Feed and Extracted Bituminuous Mix Samples, MLR-88-2, 1988

Since 1987, the Iowa Department of Transportation has based control of hot asphalt concrete mixes on cold feed gradations. This report presents results of comparisons between cold feed gradations and gradations of aggregate from the same material after it has been processed through the plant and laydown machine. Results are categorized based on mix type, plant type, and method of dust control, in an effort to quantify and identify the factors contributing to those changes. Results of the report are: 1. From the 390 sample comparisons made, aggregate degradation due to asphalt plant processing was demonstrated by an average increase of +0.7% passing the #200 sieve and an average increase in surface area of +1.8 sq. ft. per pound of aggregate. 2. Categories with Type A Mix or Recycling as a sorting criteria generally produced greater degradation than categories containing Type B Mixes and/or plants with scrubbers. 3. None of the averages calculated for the categories should be considered unacceptably high, however, it is information that should be considered when making mix changes in the field, selecting asphalt contents for borderline mix designs, or when evaluating potential mix gradation specification or design criteria changes.