Researchers
About the research
Addressing work zone crashes is critical for both the traveling public and highway workers. Two-lane two-way (TLTW) work zone configurations pose a special crash risk because the separation between opposing lanes of high-volume, high-speed, multilane traffic narrows to a head-to-head configuration. Various traffic control devices (TCDs) are used to separate opposing traffic in TLTW configurations, with each TCD having advantages and disadvantages in terms of cost, safety, and other factors. At the same time, agencies have little guidance as to when and where different configurations should be used.
The objective of this research was to assess the advantages and disadvantages of various types of TCDs used to separate opposing lanes of traffic in TLTW work zones and to provide information about their use. The first phase of this research (InTrans Project 19-720, 2019–2022) included identifying the advantages and disadvantages of various types of TCDs, evaluating the effect of different TCDs on truck lane position in Iowa TLTW work zones, and analyzing crashes in Iowa TLTW work zones.
The results of the lane position assessment in the first phase of this research yielded useful and statistically significant preliminary results. In the analysis of lateral lane position, 20% of large trucks positioned themselves over the right lane line when a portable concrete barrier (PCB) was present, compared to 4% when only tubular markers were present or 3% when curbing with tubular markers was present. Large trucks were most likely to be positioned within their lane when separated from opposing traffic by only tubular markers (73%), compared to 51% when curbing with tubular markers was used or 43% when PCBs were used (43%). The analysis of crashes in TLTW work zones that used tubular markers only or PCBs did not yield useful insights due to the small sample size.
In the second phase of this research (InTrans Project 22-804, 2022–2025), an additional evaluation of patterns in crashes on two-lane roadways was conducted to determine whether there was an inflection point above which head-on/sideswipe crashes increased. This information could be used to infer a point at which a concrete barrier would have more utility than other types of separation. Additionally, work zone crash patterns were assessed to determine whether any insight could be gained from this data source.
The methods and results of both phases are presented in the project report.