The SHRP 2 NDS is the first large-scale study focused on collision prevention (as opposed to injury prevention once a collision occurs) since the Indiana Tri-Level Study (Tri-Level Study of the Causes of Traffic Accidents: Final Report, DOT HS-805 085, U.S. Department of Transportation, May 1979). Vehicle use was recorded continuously during the SHRP 2 NDS. Information on vehicle travel, or exposure, can be extracted at the same level of detail as for safety-related events, such as crashes and near crashes. Hence, the SHRP 2 NDS is the first large-scale study to support detailed estimates of collision risk. Moreover, crashes are a leading cause of nonrecurring congestion, so collision prevention has added benefits in terms of reduced delay, fuel consumption, and emissions. The NDS provides objective information on the role of driver behaviour and performance in traffic collisions and the interrelationship of the driver with vehicle, roadway, and environmental factors. The SHRP 2 Safety research program was carried out under the guidance of the Safety Technical Coordinating Committee (TCC), which was composed of volunteer experts. The Safety TCC developed and approved all project descriptions and budgets and met semi-annually to review progress and approve any program modifications. The Oversight Committee approved all budget allocations and contract awards. Assistance was provided by expert task groups, which developed requests for proposals, evaluated proposals, recommended contractors, and provided expert guidance on many issues, such as data access policies and procedures. The decisions and recommendations of the governing committees are implemented by the SHRP 2 staff as they carry out day-to-day management of the research projects. This report details the methodology used to link the second Strategic Highway Research Program (SHRP 2) Naturalistic Driving Study (NDS) data to the SHRP 2 Roadway Information Database (RID), the final critical step in completing the SHRP 2 Safety database. The NDS data set contains extensively detailed data collected continually from more than 5.5 million trips taken by the instrumented vehicles of 3,147 volunteer drivers in six sites. The RID contains extensively detailed data on 25,000 centerline miles of roadways in these six sites, less detailed data on 200,000 centerline miles of roadways in the six states in which the sites were located, and supplemental data on topics such as crash histories, travel volumes, construction, and weather in the six states. The true power of the NDS and the RID comes when they are linked–when each trip is matched to the roadway segments that were travelled and each roadway segment is matched to the trips that travelled on it. The matching methodology documented in this report uses as input the GPS position data collected once per second by the NDS instrumentation and the NAVTEQ network of road segments of all public roads in the continental United States over which the NDS vehicles could travel. The Matching Algorithm associates each GPS point of an NDS trip with the road segment on which a vehicle travelled. The principal challenges overcome by the algorithm were to accommodate GPS readings that may drift far from the correct roadway and to be operationally efficient in comparing the 3.7 billion GPS readings with the 2.6 million NAVTEQ road segments that were traversed. The algorithm’s results are stored in a very large table that associates trip timestamps with road segments. (Author/publisher)
Samenvatting