New developments in UTMOST: Application to electronic stability control

The Unified Tool for Mapping Opportunities for Safety Technology (UTMOST) is a model of crash data that incorporates the complex relationships among different vehicle and driver variables. It is designed to visualize the effect of multiple safety countermeasures on elements of the driver, vehicle, or crash population. We have recently updated UTMOST to model the effects of the time-course of fleet penetration of vehicle-based safety measures, as well as changes in the populations of drivers and vehicle types in the fleet. This report illustrates some of the capabilities of UTMOST with examples of predicted effects for one reasonably well understood countermeasure (electronic stability control, ESC) and three countermeasures just entering the vehicle fleet (forward collision warning, FCW; road departure warning, RDW; and lane change warning, LCW). Results include the relative effects of the countermeasures on the overall number of crashes and on drivers of different ages. The report also illustrates the time-course capability of UTMOST by showing year-to-year savings in serious injuries and fatalities for a driver-based countermeasure (increased belt use), which would have an immediate effect throughout the vehicle fleet, compared to ESC, which as a vehicle-based countermeasure would affect new vehicles as they enter the fleet.The University of Michigan Sustainable Worldwide Transportationhttp://deepblue.lib.umich.edu/bitstream/2027.42/64278/1/102395.pd

Predicting mirror adjustment range for driver accommodation

Although the question of how large a driver's outside rearview mirror must be in order to see a specified target has been addressed in other publications, the related problem of required adjustment range has not. In this paper, we present a series of equations that predict, for a given vehicle, the size and location of the mirror adjustment range needed in order to accommodate some percentage of the driver population (e.g., 96%). To complete the calculations for 96% accommodations, eye locations in the vehicle are represented by the 99% SAE J941 eyellipse. Because the transformation from eye location to target location in the mirror will not preserve the tangent properties of the eyellipse, we propose a method in which the side and plan views of the eyellipse are treated separately. Eye location in plan view affects only horizontal adjustment of the mirror, and eye location in side view affects only vertical adjustment of the mirror. In each view, there are two points that lie on lines that are tangent to the eyellipse and pass through the mirror center. These two points are used to represent two extremes of mirror adjustment. Thus, we exclude the 2% of driver eye locations that lie outside either of the tangent lines (no cases lie outside both, so each tangent excludes 1%). In plan view, eye locations must first be adjusted for head turn. We also present equations to calculate mirror adjustment, referenced to an arbitrary line, for each of the four tangent points, given a specified target. We discuss various choices of target location and type, including centered point targets, centered extended targets, and targets that are located at the edge of the field of view. For the latter target type, the calculation of head turn is somewhat different than for centered targets, but the rest of the calculations are the same. The end result of these equations is a rectangle in two-dimensional mirror-adjustment space such that 96% of drivers can find a suitable mirror position within those bounds. An example is carried out using dimensions from a specific vehicle and a target located at the inner edge of the field of view, in order to illustrate the procedure.Michigan University, Ann Arbor, Industry Affiliation Program for Human Factors in Transportation Safetyhttp://deepblue.lib.umich.edu/bitstream/2027.42/49385/1/UMTRI-98-45.pd

UTMOST: a tool for comprehensive assessment of safety benefits

This report describes a software tool that is being developed at UMTRI to represent the effects of nonindependent safety measures (the Unified Tool for Mapping Opportunities for Safety Technology, UTMOST). The tool has as its core a model representing crashes in terms of precrash conditions, occupant characteristics, crash type, and outcome. Overlaid on this is a model of the effect of implementing each of a number of safety measures, including public policy and technological measures. This portion of the model allows for visualization of the potential benefits of various approaches and combinations of approaches to safety. UTMOST is being developed and validated using existing U.S. crash databases for the purpose of understanding future safety trends in the U.S., as well as current differences between the U.S. and selected other countries, and future trends in those countries. Our goal is to be able to use this model to: 1) predict the benefit of specific changes in policy or technology in the context of other safety measures; 2) describe the largest remaining problems after a policy or technology has been implemented; and 3) assess the overall safety performance of individual vehicles, both in general and with respect to particular demographic groups.The University of Michigan Strategic Worldwide Transportation 2020http://deepblue.lib.umich.edu/bitstream/2027.42/61189/1/99833.pd

Driver distraction from cell phone use and potential for self-limiting behavior

This project consists of three parts. The first is a review of the literature on driver distraction that primarily focuses on cell phone use. The second two parts involve analysis of an existing field operational test (FOT) database to examine: 1) self-limiting behavior on the part of drivers who use cell phones, and 2) eye glance patterns for drivers involved in cell phone conversations and visual-manual tasks (e.g., texting) as compared to no-task baseline driving. The literature review discusses the apparent contradiction between results of case-crossover and simulator studies that show increases in instantaneous risk due to talking on a cell phone and results of crash-data analyses that show no substantial increase in crashes associated with increases in cell phone use in vehicles. The first data analysis shows some evidence of self-limiting behavior in cell phone conversations. Drivers initiate calls when on slower roads and at slower speeds, often when stopped. However, they call more at night, which is a higher-risk time to drive. The second analysis showed that eye glances when talking on the phone are fixated on the road for longer periods of time than in baseline driving. In contrast, on-road eye glances when engaged in a visual-manual (VM) task are short and numerous. Eye glances on and off the road are about equal in length, and the average total off-road gaze time for a five-second interval is about 2.8 secs, or 57% of the time. Average off-road gaze time out of five seconds in baseline driving is about 0.8 sec, or 16% of the time. Results show the differences in distraction mechanism between cell-phone conversations and texting. Ramifications for potential interventions are discussed.State Farm Insurancehttp://deepblue.lib.umich.edu/bitstream/2027.42/108381/1/103022.pd

Improving the repeatability and reproducibility of belt fit measurement with 6YO and 10YO ATDs

In previous work, researchers at the University of Michigan Transportation Research Institute (UMTRI) developed a method for quantifying the belt fit provided by belt-positioning boosters by measuring the belt location relative to the six- and ten-year-old Hybrid-III dummies. In another study, the torso and lap belt scores obtained by this method were found to be closely related to the belt fit obtained by similar-size children across a wide range of booster and belt conditions. The Insurance Institute for Highway Safety (IIHS) adapted the UMTRI procedure to develop a rating system for booster belt fit, but adoption by other labs has been slowed by difficulty in obtaining repeatable results. The current study was undertaken to improve the repeatability and reproducibility across operators of the procedure. The modifications made by IIHS were studied and most incorporated, and a number of other issues were examined through pilot testing. A revised version of the procedure was tested with repeated measurements by three operators in six boosters. The results were analyzed to quantify the variance associated with the operators, the installation of the booster and dummy, and the routing of the belt. The results show that trained operators can perform the procedure with minimal systematic bias across boosters. The variability within booster varies considerably, with some boosters producing higher precision measurements due to the design of their belt-routing features. For any particular booster, the booster and dummy installation process accounts for about half the variability in the belt fit scores with the remainder due to variability in the belt routing and other measurement variability. Based on these findings, multiple measurements of belt fit in each booster are recommended to establish the desired level of confidence in the true belt fit. Straightforward statistical methods involving confidence intervals are recommended for establishing objective test methods. More testing will be needed to determine the reproducibility of the method across laboratories.National Highway Traffic Safety Administrationhttp://deepblue.lib.umich.edu/bitstream/2027.42/89866/1/102812.pd

LATCH usability in vehicles

This project investigated the usability of Lower Anchors and Tethers for CHildren (LATCH) hardware by measuring LATCH implementations in 98 2011 or 2010 model-year vehicles. ISO and SAE LATCH usability rating systems were used to assess all vehicles using data from the second row left position. Child restraint/vehicle interaction was assessed using both ISO and NHTSA proposed procedures. Volunteer testing was performed with 36 subjects on 12 different vehicles using 3 different child restraints, with each subject performing 8 child restraint installations. The results from the vehicle survey indicate that most vehicle manufacturers provide LATCH hardware at only the minimum number of locations required by FMVSS 225. Only 7 vehicles had three sets of LATCH hardware in the second row, while most of the remaining 91 vehicles were only equipped with LATCH in each outboard position and a tether anchor in the center position. In the 21 vehicles with a third row, four had no tether anchors and 11 had no lower anchors in the third row. The SAE child restraint fixture could not be installed in 27 vehicles, although head restraint interference was the cause of interference in only one vehicle. Fifty-nine vehicles met the SAE recommended lower attachment force of 75 N (16.9 lb) or less, while 15 vehicles required forces from 2 to 8 times this value. Only 2 vehicles met SAE recommendations for clearance angle of at least 75 degrees around the lower anchors. The depth of the lower anchors relative to the bight is less than 2 cm in 28 vehicles, 2-4 cm in 34 vehicles, and greater than 4 cm in 36 vehicles. The most common location for the tether anchor is the seatback (42) and package shelf (35). The lower anchors are marked in 77 vehicles, while the tether anchors are marked in 68 vehicles. Only Ford products clearly specify weight ranges for use of LATCH hardware in their manuals. Many vehicle manuals are not clear on how the head restraint should be positioned during child restraint installation. ISO ratings of vehicle LATCH usability ranged from 41% to 78%, while vehicles assessed using the SAE draft recommended practice met between 2 and all 10 of the recommendations. There was a slight correlation between vehicles meeting SAE recommended practices and ISO usability ratings. Twenty vehicles with a range of vehicle features were assessed using the ISO vehicle/child restraint form and 7 child restraints; ISO vehicle/child restraint interaction scores ranged from 14% to 86%. Based on these interaction scores, the Cosco Alpha Omega, the Chicco KeyFit, and Evenflo Maestro were used with a subset of 12 vehicles to perform volunteer testing and assess the quality of subject installations. No vehicle factors predicted tether use or correct use of tether. However, the correct use of lower anchors was associated with a lower anchor clearance angle greater than 54°, an attachment force of 40 lb or less, and lower anchor depth within the bight of less than 2 cm. Correct lower anchor use also had 3.3 times higher odds of tight installation compared to incorrect use.Insurance Institute for Highway Safetyhttp://deepblue.lib.umich.edu/bitstream/2027.42/90856/1/102854.pd

An examination of the Michigan 2010 motor vehicle traffic crash fatality increase

In 2010, national fatal crash counts went down by 3.5%, following on the heels of substantial drops in 2008 and 2009. However, in Michigan, fatal crashes were down substantially in 2009, but up by nearly 8% in 2010. This report contains an in-depth look at the patterns associated with Michigan’s fatal crash increase in 2010. In particular, we present a time series analysis of fatal-crash trends over the last 40 years. In addition, we provide breakdowns of crash subcategories, focusing on alcohol and drug use by drivers, commercial vehicles, young and elderly drivers, motorcycles, and construction-zone crashes. Finally, we compare the pattern in Michigan to the patterns of fatal crashes for three other states. The primary result of these analyses is that 2009 was unusually low in fatal crashes and 2010 represents a return to normal numbers. That said, fatal-crash-involved drivers testing positive for blood THC have more than doubled in 2010. In addition, construction zone crashes have increased, though the base numbers are too low to determine whether the increase is significant. Motorcycle fatalities showed large increases in 2010, especially in collisions with other motor vehicles. In the multi-state comparison, the nearest state, Wisconsin, showed the same 2009 decrease and 2010 increase in total crashes, while more distant states of Idaho and Missouri showed steady decreases. These results are consistent with regional trends reported by NHTSA. The four states showed similar results with steady decreases in overall crashes and steady increases in drug-related fatal crashes.Michigan Office of Highway Safety Planninghttp://deepblue.lib.umich.edu/bitstream/2027.42/89936/1/102816.pd