Addressing Encroachment-Related Safety Issues in Work Zones: A Guide (2023)

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24 Considerations and Limitations One conclusion reached by the research team was that there is not sufficient evidence to support the need to revise current guidelines pertaining to impact conditions in MASH. As explained previously, this conclusion was supported by a variety of observations, some of which related to lack of data and/or differences in data collection. For example: • There are not enough data to support the need for a change in MASH speed impact conditions for testing and evaluating roadside safety hardware implemented in WZ locations. – Only five WZ related crashes with reconstructed impact speed were identified in the NCHRP Project 17-43 database. – The posted speed limits and the functional classification for the roadways on which these encroachments occurred are not available in the NDS data. – There may be differences associated with the different data collection periods of the utilized datasets and the relative contribution of advancing vehicle safety technologies in each. • There are not enough data to support the need for a change in MASH angle impact conditions for testing and evaluating roadside safety hardware implemented in WZ locations. – Only eight WZ related crashes with reconstructed impact angle were found. – The encroachment angles obtained from NCHRP Project 17-43, NCHRP Project 17-22, and NDS data were fairly different, potentially due to the manual technique utilized to extract the encroachment angle values directly from videos as part of the NDS data effort. • The encroachment conditions extracted from the NCHRP Projects 17-43 and 17-22 databases are based on ROR crashes, while the NDS data are based on encroachments, most of which did not result in a crash. C H A P T E R   5