1. Graduate Research Assistant, Traffic Operations and Safety Laboratory, Dept. of Civil and Environmental Engineering, Univ. of Wisconsin–Madison.
2. Scientist I, Traffic Operations and Safety Laboratory, Dept. of Civil and Environmental Engineering, Univ. of Wisconsin–Madison.
3. Associate Director, Traffic Operations and Safety Laboratory, Dept. of Civil and Environmental Engineering, Univ. of Wisconsin–Madison.
4. Professor and Executive Associate Dean, Traffic Operations and Safety Laboratory, Dept. of Civil and Environmental Engineering, Univ. of Wisconsin–Madison.