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Setting Work Zone Speed Limits

Status: Complete

Description: Increasing travel demands and an aging highway infrastructure drive the need for extensive construction, maintenance, and utility work zones. The introduction of work zone environments creates risks for both drivers and construction workers due to changes from the normal driving environment. Temporary speed limit reductions are a common countermeasure aimed at improving work zone safety. In theory, reduced speed limits may serve at least three important functions: reduce variability in travel speeds and the potential for work zone crashes, reduce average travel speeds and the severity of crashes when they do occur, and enhance worker safety. Thus, understanding how reducing work zone speed limits impacts travel speeds is an important task. This project evaluates the impacts of speed limit reductions on driversÂ’ speed selection at both aggregate and disaggregate levels. Data were collected from nine construction work zones in Iowa during 2014 and 2015. The lack of availability of data pertaining to the location, time, and type of activity significantly constrained the level of analysis that could be conducted for this research. Therefore, the crash analysis was not deemed reliable due to the inconsistency among the multiple data sets that were used to determine the location, time, and type of work zone activity. For the speed analysis, a quantile regression model was employed to examine the impacts of speed limit reductions on speed distribution quantiles before and during construction activities. The results show that speeds are consistently reduced when work zone speed limits are in place.

Report: setting_work_zone_speed_limits_w_cvr.pdf 2.44 MB (published 2017)

Other Document: Setting Work Zone Speed Limits 334 KB *pdf

State conducting research: Nebraska


  • Sharma, Anuj (Iowa State University)
  • Savolainen, Peter (Iowa State University)
  • Huang, Tingting (Iowa State University)
  • Roy, Sneha (Iowa State University)
Iowa State University does not discriminate on the basis of race, color, age, ethnicity, religion, national origin, pregnancy, sexual orientation, gender identity, genetic information, sex, marital status, disability, or status as a U.S. veteran. Inquiries regarding non-discrimination policies may be directed to Office of Equal Opportunity, Title IX/ADA Coordinator and Affirmative Action Officer, 3410 Beardshear Hall, 515 Morrill Road, Ames, Iowa 50011, Tel. 515 294-7612, Hotline: 515-294-1222, eooffice@iastate.edu.