United States Department of Transportation
i
Exploration of the SHRP2 naturalistic driving study data to identify factors related to the selection of freeway ramp design speed.
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2017-03-01
[PDF-1.52 MB]
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Abstract:This research explored the second Strategic Highway Research Program (SHRP2) Naturalistic Driving Study (NDS) database for the potential to identify freeway entrance and exit ramps and teen drivers’ behavior while traveling those ramps. This is in advance of a future task on NCHRP Project 15-56, the objective of which is to review current practices for selecting design speed on freeway ramps and, if beneficial, recommend changes to those practices. By exploring the features of the NDS dataset, researchers can a) consider a new tool for study site selection based on roadway characteristics and b) identify a potential new source of data that can either serve as a basis for analysis or serve as a comparison or validation of field data that researchers will collect through other methods.
Researchers reviewed each of the 1156 variables in the 21 data dictionaries in the NDS database, as well as the seven components of the related Roadway Information Database (RID), to identify variables with potential for use in identifying freeway ramps and obtaining further information on driver and vehicle characteristics while traveling on those ramps. Researchers also conducted a query of the NDS database to look for all of the crash, near-crash, and crash-relevant events in the NDS database that could have occurred on ramps, identifying 939 events from 917 trips. A detailed review of the records from those 939 events revealed that only 49 occurred on a freeway ramp, 48 of which were categorized as near-crashes and one was a crash in which the subject driver drove over road debris.
Results from these reviews led researchers to conclude that further exploration of the questions relating design speed to vehicle performance and driver behaviors would require the use of, and purchase of, the more detailed dataset that must be requested from the NDS project administrators. Additional conclusions and recommendations from the research team are also offered within the report.
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