Feb 18

Modern Roundabouts: Intersections Designed for Safety

Event Details

Ames, Iowa


Institute for Transportation (Map)
2711 S. Loop Drive, Suite 4700 (Room 4040)
Ames, IA 50010


February 18, 2020


Registration at 8:00 a.m.
Workshop starts at 8:30 a.m.



Event Contact
Keith Knapp
InTrans, Iowa LTAP

Course Overview

The modern roundabout is a proven strategy for improving the safety and operations of intersections. The physical characteristics of a well-designed modern roundabout reduce the frequency and severity of intersection crashes for all users including pedestrians and bicyclists. This course highlights the benefits of modern roundabouts and gives participants the fundamental knowledge needed to plan and consider applying roundabout intersection projects in their area. This course is an introductory level course with a blend of technical and non-technical planning, design, and operations considerations.

Upon completion of the course, participants will be able to:

  • Distinguish a modern roundabout from other types of circular intersections
  • Describe the safety advantages of roundabouts
  • Describe the operational advantages roundabouts provide
  • Identify what type of locations roundabouts may be appropriate
  • Describe strategies to overcome common barriers to implementation of roundabouts, such as negative public perceptions
  • Describe the key considerations when planning an area’s first roundabout
  • Apply basic traffic operational models and capacity calculations for roundabouts
  • Describe key geometric design principles of a modern roundabout
  • Apply signing and marking suggested practices
  • Apply design strategies for pedestrians and bicyclists


Richard Retting has served as Safety & Research Practice Leader for Sam Schwartz Consulting since 2008. He was instrumental in producing the widely-cited 2001 IIHS landmark study that found that modern roundabouts reduce traffic fatalities by 90 percent and injury crashes by 76 percent.

Mr. Retting has 38 years of multidisciplinary traffic safety operations and research experience and is a widely recognized North American expert on traffic safety. Mr. Retting has served as Principal Investigator or Co-Principal Investigator for more than 200 traffic safety research projects conducted for FHWA, NHTSA, TRB, IIHS, and GHSA. Mr. Retting has deep subject matter knowledge and practical experience related to analyzing and mitigating traffic crash problems, and as authored more than 100 scientific publications. He is a Fellow of ITE, Chair of the ITE Vision Zero Steering Committee, and member of both the TRB Standing Committee on Safety Data, Analysis, and Evaluation and the TRB Standing Committee on Traffic Law Enforcement.

At the Insurance Institute for Highway Safety, Mr. Retting served as Senior Transportation Engineer, which included responsibility for conducting research into causes and injury mechanisms of motor vehicle crashes; evaluating effectiveness of crash and injury countermeasures; analyzing data; and building consensus on complex traffic safety issues.

At New York City DOT, Mr. Retting served as Deputy Assistant Commissioner for Traffic Safety Programs, where he oversaw Safety Engineering and Safety Education programs and had responsibility for development and implementation of New York’s Highway Safety Improvement Program, Strategic Highway Safety Plan, and Corridor Safety Program.