Trucks are critical to economic connectivity in rural states like North Dakota. They are a flexible alternative to rail and pipeline in sourcing and delivering goods. Trucks also serve a vital role in local rural economies. Trucks enable natural resource-based industries, such as agriculture and oil, to consolidate products for longer distance shipment in rail and barge where they can gain economies in larger shipment sizes. Trucks also are a primary mode for many local processes in gathering inputs and distributing products. Therefore, truck traffic is heavily influenced by local economic activity and larger national economic trends. Unusual increases in truck traffic, such as that related to economic change or natural disaster, may create unintended crash risk. As changes in traffic volumes and patterns are recognized, levels and effects of increased safety for truck heavy corridors and truck related traffic must be monitored. Nationally, trucks are involved in about 285,000 crashes annually. About 1 in 100 crashes resulted in fatal injury between 2010 and 2012 (Federal Motor Carrier Safety Administration 2014). The median for the 48 contiguous states was 0.14 fatalities per 100 million VMT. States with rates in the upper quartiles for crash-incidence rate are shown in the orange and red categories in Figure 1.1. State-level crash incidence shows geographic disparity, ranging from 0.46 per 100 million vehicle miles travelled (VMT) in North Dakota to 0.03 fatalities per 100 million VMT in Rhode Island (Federal Highway Administration 2014; National Highway Traffic Safety Administration 2014). Figure 1.1 also shows that many states in the central region experience relatively high truck crash incidence. When reviewing annual crash event figures, it is evident that large truck-involved crashes have become increasingly prominent in North Dakota. Oil exploration and development in the western region of the state has been the nexus for exponential growth in truck traffic. Trucks are used extensively in drilling and production phases. While trucks are commonly used in the drilling phase, the heavy reliance on trucks in oil-movement-to-rail-transfer facilities and pipeline facilities is atypical, considering the traditional industry supply chains. The majority of U.S. oil production is transported by pipeline from production point to consumption facilities (Figure 1.2). Nationally, about 9% of crude oil and petroleum products were moved by rail in 2014 compared to about 60% by rail in North Dakota (U.S. Energy Information Administration [EIA], ND Pipeline Authority 2015). Market maps published for 2012 and 2013 show transitions from rail to pipeline transport at wellhead (ND Pipeline Authority 2015). In addition, some local gathering pipeline-to-rail facility transport has been added, but a substantial reliance on truck-to-rail facilities continues to be reported in local traffic. Most likely, the increased truck density will be a sustained traffic environment in the oil region for many years. Therefore, it is an opportune time to draw knowledge from crash events over recent years to more effectively address this critical safety issue. This study emphasizes injury crashes. Injury crashes, which include fatal injury crashes, were selected as the unit of study because of the more serious nature of these crashes. While property-damage-only crashes also may provide insight, previous experience has shown that injury crashes perform well in profiling and understanding a smaller number of serious crash events that end in disabling and fatal injury outcomes. Injury crash trends in North Dakota show a pronounced increase in truck involvement (Figure 1.3). In comparison, the number of injury crash events for other vehicles also have trended upward, but at a slower rate. Overall, injury crash events involving trucks increased about 300% from 2004 to 2014. Other injury crashes increased only about 3% during the same period. A larger increase in truck crash events can be expected given the differences in the rate of increase for the traffic, but figures show a disproportionately large increase in crashes relative to the traffic increase (ND Department of Transportation 2015). This dissimilarity in crash rates is consistent with findings in Europe that show the crash fatality rate increased as truck fleet density increased, while the same effect was not found for the car fleet (Castillo-Manzno et. al 2015). The higher crash rates in proximity to drilling activity also is consistent with experiences in Pennsylvania where heavily drilled counties experienced fatal and injury crash rates about 46% greater than non-drilling counties (Graham et. al 2015). The trends in incidence rates for injury crashes involving trucks and those not involving trucks, as vehicle type reported in the law enforcement crash form, were graphed (Figure 1.4). North Dakota requires that traffic crashes are reported to law enforcement if injury results and/or damage exceeds $1,000. Although property-damage-only crashes may be under-reported, it is reasonable to assume that law enforcement-reported injury crashes closely represent the population, due to the more serious nature of the crashes. Trucks retain lower overall injury crash incidence rates than other vehicles. Given that commercial truck drivers have specialized driver training and adhere to federal standards in their driving practices, this lower crash rate is expected for the professional driver group. A significant difference was found in the crash incidence associated with trucks compared to other traffic crashes in this measure over time (Chi-Sq.=461.54, df=10, p=<0.001). When standardized by VMT, the trend for other injury traffic crashes shows a decline, while the truck-involved crashes trends upward until 2012. The trends do appear to have levelled in recent years. Based on regression analysis of the limited data set covering the number of crash events and miles travelled annually between 2002 and 2014, a 10% increase in VMT on state highways results in a 15% increase in truck injury crash involvement. The VMT explained 98% of the variation in the crash event involvement, with significance at the 99th percentile. With the other vehicle crash events, the VMT had much lower explanatory value and the coefficient was not significant at the 99th percentile. This significant relationship supports the premise that crash risk is positively associated with truck traffic density. The relative risk for truck crash risk has increased most rapidly in the northwest quadrant of the state. This area is the epicentre of oil and gas development. Seventeen counties in western North Dakota define the oil region, considering well locations and transportation, as illustrated in Figure 1.5. Three counties heavily active in the oil production are McKenzie, Mountrail, and Williams. This trio of counties, located in the northwest quadrant, accounts for about 72% of the state’s current oil production (Department of Mineral Resources, Oil and Gas Division 2015). Figure 1.6 shows how heavily truck safety in this area impacts the state-wide truck crash trend depicted in the previous illustrations. Exponential growth in truck crash incidence in the northwest seems to have peaked in 2012. It will take several years to determine whether safety improvement, shown in the declining trend, can be sustained. It is reasonable to expect that changes in infrastructure, education, and enforcement that address the truck-involved crashes in the region will have a positive impact. More recently, lower oil prices also appear to be stemming truck traffic growth. The southwest region includes Dunn County, which is among the four largest oil-producing counties. This region has experienced higher truck-involved crash incidence compared to 2009, but not nearly the same magnitude in increase. The eastern regions truck-involved crash trend lines are relatively stable. As noted, in a comparison of truck crashes to other vehicle crashes, trucks are involved in a relatively small share. The significant differences found in crash incidence and severity likelihood, suggests that attention to the issue may be especially beneficial in improving traffic safety. There were about 106,000 crashes on North Dakota roadways between 2009 and 2014, with 7% involving trucks as at least one of the vehicles in the crash. Trucks were involved in 10% of the 22,000 injury crashes during this five-year period. Truck crashes are associated with a greater share of the more serious injury outcomes than crashes not involving trucks. In regard to severe injury crashes, which includes fatal and disabling injuries, trucks were involved in 20% of the reported crash events in the state. An investigation into reported-injury crashes in North Dakota involving trucks was conducted. Findings offered insight into truck crashes as a traffic safety issue, since it is likely trucks will continue to attribute a larger proportion of vehicle type, especially in certain traffic corridors seasons. The following literature review provides a brief overview of current knowledge about truck crash risk factors. Descriptive analysis is used to relay basic facts about truck crash event from multiple sources. Section four describes the method and data used to model crash severity risk factors. Model results and discussion are provided in the final sections of the paper. (Author/publisher)
Abstract