Wednesday, November 30, 2022

For more than two decades, the Iowa DOT has been encouraging Iowa communities to consider converting certain four-lane streets to three lanes (also known as a “road diet”) with the aim to improve safety and reduce crashes. 

Two areas of concern often raised by communities are the impacts on businesses and on emergency response. In a project recently completed for the Iowa DOT, a team of researchers including Michelle Reyes, senior research associate at NADS, and Cara Hamann, PhD, of the Iowa Injury Prevention Research Center (IPRC), investigated these impacts by surveying businesses and emergency responders in Iowa communities with recent lane conversions. In addition, they analyzed data from the Cedar Rapids Fire Department to determine whether response times had been affected by the lane conversions.

The top findings included:

  1. One-third of the business respondents reported positive or slightly positive effects, and another 38% thought the road conversion had no impact on their business.
  2. Emergency responders had divided opinions: 34% disagreed with keeping the conversion in place, while 30% agreed, and 28% were neutral.
  3. Community education about what to do when emergency vehicles are on the road is important. Many responders with negative perceptions reported that drivers didn’t know where to move to yield to the responders, resulting in blocking lanes and slowing response. 
  4. Analyses that controlled for speed limit, number of lanes, traffic signals, peak traffic times, and season found that the lane conversions had no measurable impact on fire department response times in Cedar Rapids. 

You can visit the Iowa DOT website to learn more about 4- to 3-lane road conversions.

Other ongoing traffic safety research projects

“Long-standing collaborations are essential to many of our projects,” notes Reyes, whose efforts often focus on safety and crash data research and analysis. Two longstanding partners for traffic safety research are the Iowa DOT and the University of Iowa Injury Prevention Research Center (IPRC). Other related projects from the past year include:

  • Effect of Seat Belt Use on Injury Severity for Adult Rear-Seat Occupants Injured in Motor Vehicle Crashes: Analysis of Iowa crash data from 2016–2019 found, in part, that odds of a fatal injury were 6.2 times higher when adults in the rear seat were unbelted.

                Sponsor: Iowa DOT; Partners: IPRC, Governor’s Traffic Safety Bureau

  • A Crash Data Dictionary was developed to document the data elements collected on the Iowa crash report form. The NADS/IPRC team reported hundreds of findings, some of which are being implemented now, that have the potential to improve crash data quality in the future. 

                Sponsor: Iowa DOT; Partners: IPRC, Governor’s Traffic Safety Bureau

  • Instrumented Farm Vehicle Roadway Study: GPS/video devices were installed on Iowa farm equipment that collected data and recorded vehicles as they approached, followed, and began to pass farm equipment. 

                Sponsor: CDC/NIOSH and UI Great Plains Center for Agricultural Health; Partner: Iowa State University InTrans