Sustained and halo effects of various speed reduction treatments in highway work zones

Ali Hajbabaie, Juan C. Medina, Ming Heng Wang, Rahim Ray F. Benekohal, Madhav Chitturi

Research output: Contribution to journalArticlepeer-review


This paper analyzes the speed reductions achieved with the use of an automated speed photo-radar enforcement (SPE) system in highway work zones. A comparison with the following three traditional treatments used to reduce speeds is also presented: (a) a speed feedback trailer (trailer treatment), (b) a police patrol car (police treatment), and (c) the combination of a police patrol car and a speed feedback trailer (police-trailer treatment). The results indicated that the SPE system and police-trailer treatments reduced the mean speed of both the general traffic stream and free-flowing vehicles by about 5 to 7 mph. The magnitudes of the speed reductions while the treatments were deployed were sustained over time. Police presence alone also reduced the speed significantly but to a lesser degree, and the effects of the trailer treatment alone were limited. The frequency and the degree of speeding were also influenced by the treatments to various degrees. The proportion of drivers speeding by more than 10 mph was reduced by 8.7% by the SPE system treatment and by 8.9% by the police-trailer and police treatments, which brought the rate of speeding down to 0.2% for the SPE system treatment and 0% for the police-trailer and police treatments. These treatments also reduced the frequency of speeding by 10 mph or less by 36% to 46%. The halo effect for the SPE system after the treatment was removed was limited to a reduction in the mean speed of 2 mph or less, and that for the police treatments was not significant.

Original languageEnglish (US)
Pages (from-to)118-128
Number of pages11
JournalTransportation Research Record
Issue number2265
StatePublished - Dec 1 2011

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Mechanical Engineering


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