Crash Data Reporting and Analysis – an Oregon Case Study
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Crash Data Reporting and Analysis – An Oregon Case Study Shazia Malik, Robert L. Bertini, Christopher M. Monsere Abstract. Motor vehicle crash underreporting is a serious problem as it masks the total impact of highway crashes and may skew our understanding of high crash frequency locations and the need for appropriate countermeasures. It is generally understood that highway crashes are underreported, but the extent of the underreporting is often not clear. Using a case study along one Oregon highway, this paper estimates the magnitude of crash underreporting during 2000. The crashes reported by the Oregon Department of Transportation (ODOT) for a state highway (OR-18) were compared with the record of crashes as reported by an incident management program. Several parameters such as location, time of day and crash description were used to determine whether the same crash had been recorded by the two independent data sources. Crash data are compiled by ODOT from individual drivers and police crash reports. The roving incident responders attend to incidents/crashes on the highway and dispatch the information to the traffic management center through a computer aided dispatch system. Presently there is no mechanism that combines the two data sources. Given that many states now have incident response programs in place, suggestions are provided regarding how useful information can be extracted and archived in order to improve the compliance rate for statewide crash reporting. BACKGROUND The Oregon Department of Transportation (ODOT) has summarized motor vehicle crash records since 1941 and began publishing crash data in 1948. The ODOT Crash Analysis and Reporting (CAR) Unit compiles crash data from individual driver and police crash reports submitted to the Department of Motor Vehicles (DMV) as required by Oregon state law. These data are stored in a database and summaries are published annually. Like most states, the state of Oregon has set threshold limits for crash reporting based on the estimated property damage and personal injury. Oregon law currently requires that any crash on a public roadway resulting in a fatality, bodily injury or damage to one person’s property in excess of $1,000 be reported to the DMV. In Oregon, submittal of crash report is the responsibility of the individual driver. However, approximately 33% of all reported crashes are also investigated by a police officer. As part of its traffic management function, the Oregon DOT has developed an Incident Response (IR) program. The program was originally developed for the urban freeways of Portland but has since been expanded to include the less metropolitan southern Willamette Valley. ODOT Region 2, which is responsible for this area of the state, has assigned incident responders to patrol several key highway segments, assisting state and local police forces and individual motorists during a wide variety of traffic events. Incidents include crashes, breakdowns, spilled loads or other random events that reduce the capacity of the road leading to vehicular delays. Incident management is a critical public safety and traffic management technique. The IR personnel help relieve non-recurrent congestion through quick incident detection, verification, response, and removal/clean up. In addition, the IR personnel notify the proper authorities, through the traffic operations center (TOC), of other types of roadway problems that will impact traffic flow or the safety of motorists or responders. Each incident is recorded in a computer aided dispatch (CAD) database. Oregon Route 18 (OR-18) is one of the key routes managed by the IR program and was chosen for analysis. OR-18 has a length of 51 miles and is a rural, mostly 2-lane highway. There are some short sections with 4 lanes that account for a total of almost 6 miles of the route. The highway passes through four counties: Lincoln, Tillamook, Polk, and Yamhill. OR-18 serves as the main route between Salem, the state capital, in the Willamette Valley and the Pacific coast. The corridor serves tourist destinations amongst them being the Spirit Mountain Casino at Grand Ronde. Figure 1: Route 18 Location Map Figure 1 shows a map of ODOT Region 2, highlighting the location of OR-18. Along this route there is also a 19-mile safety corridor between Grand Ronde and Sheridan. This section was declared a safety corridor in 1996 due to a large number of fatalities. Traffic crashes on OR-18 claimed three lives in 1995, three in 1996, two in 1997, six in 1998, and eleven in 1999. In addition to these fatal crashes, all types of crashes have been reported to account for almost 75% of the non-recurrent delay along this corridor. The Valley Junction Automatic Traffic Recorder (ATR) recorded a mean average daily traffic (ADT) of 22,000 vehicles per day for all weekend days in 2000 along this section of OR-18 (see Figure 1). The ADT increased 33% between 1995 and 2000 with no increase in the capacity of the facility (Bertini et al., 2001). Thus, in Oregon, for certain highways, there are two separate and distinct sources of crash data: (1) the statewide crash data maintained by the ODOT; (2) the crashes reported by the IR program on the days, times and at the locations they are actually patrolling. Unreported crashes (those not in the state's database) can be considered of two types: 1) those that meet the minimum threshold and are not reported; and 2) those that are not required to be reported. It is well known that not all qualifying crashes occur in both of these categories. However, what is not known is the extent to which it occurs, or what portion of the total crash picture is represented by unreported crashes. Figure 2 presents a Venn diagram showing the total crash sample space for a region where an IR program is operational. The area shown is not meant to represent scale, rather it is for graphical purposes only. Total crashes that occur include crashes recorded by the ODOT only is represented by area ‘a’, the IR personnel only by area ‘i’, those recorded by both the IR personnel and the ODOT by area ‘b’, those that do not meet the minimum threshold for reporting by area ‘m’, and an unknown component of area ‘a’. The unknown crashes, shown by hatched lines in Figure 2, are neither reported to ODOT nor captured by IR and yet meet the minimum threshold for crash reporting. m a b i Figure 2: Total Crashes in a Region The objective of this paper is to fuse data reported by IR personnel with data reported to ODOT for the year 2000 by cross-correlation. The potential magnitude of crash data underreporting is thus estimated. For the purpose of this paper, the crashes reported through the Region 2 IR were referred to as “Incident” data and the ODOT CAR data were referred to as “ODOT” data. The contents of this paper include a literature review on crash data underreporting followed by a general description of the Incident data and ODOT data used in this study. This is followed by a description of the preparation of Incident and ODOT data for matching purposes. There is a section devoted to describing how the Incident data were matched with ODOT data before the final results and conclusions are presented. CRASH UNDERREPORTING LITERATURE REVIEW There is a substantial amount of literature available on the subject of road crashes that acknowledges the problem of crash underreporting. One recent study (U.S. DOT, 2002) estimated that there were 41,821 fatal crashes, 5.3 million injury crashes, and 28 million property damage only (PDO) crashes in the United States including both police-reported and unreported crashes in 2000. It was also estimated that 21% of these injury crashes and half of the PDO crashes were not reported. The total estimated cost of all motor vehicle crashes (reported and unreported) for the same year was $230.6 billion including $25.6 billion (11%) attributed to travel delay. This total was equivalent to approximately $820 for every U.S. citizen and 2.3% of the U.S. Gross Domestic Product. The study used several data sources, including the Fatality Analysis Reporting System (FARS), to estimate the number of fatal crashes on U.S. public roads. It was noted that although the FARS census provides an accurate count for fatalities, there is no equivalent data source for injuries. The actual injury count was estimated from several other sources, including the Crashworthiness Data System (CDS), the General Estimates System (GES), the National Automotive Sampling System (NASS), the National Health Interview Survey (NHIS), and injury estimates provided to the Federal Highway Administration (FHWA) by individual states. Several methods were used to combine these data to provide a more realistic estimate for injury related crashes. The study applied the ratio of PDO involved vehicles to injuries to the 2000 injury total to estimate actual PDO crashes that likely resulted. Finally, it was concluded that underreporting likely occurred when the injured party was at fault and did not wish to involve police due to concerns about insurance or legal repercussions, or when minor bicycle or pedestrian injuries occurred. Also, a variety of administrative, clerical, or procedural errors may result in the injuries being unrecorded. For example, life flight or ambulance transport may occur prior to police arrival, or information on the injured parties may not be provided to police. Estimates of unreported injuries vary by injury severity with nearly one quarter of all minor injuries and almost half of all PDO crashes remaining unreported. In contrast, it is believed that all critical or fatal injuries are properly reported. In the Nationwide Personal Transportation Survey (Hu and Young, 1990) differences between crashes for which police reports were filed and those for which no police reports were filed were estimated.