Do High Visibility Enforcement programs affect aggressive driving behavior? An empirical analysis using Naturalistic Driving Study data.

This paper investigates the effect of High Visibility Enforcement (HVE) programs on different types of aggressive driving behavior, namely, speeding, tailgating, unsafe lane changes and 'other' aggressive driving behavior types (occurrence of not-yielding right-of-way and red light or stop signs violations). For this purpose, the Second Strategic Highway Research Program (SHRP2) Naturalistic Driving Study (NDS) data are used, which include forward-facing videos and time series information with regard to trips conducted at or near the locations of HVE implementation. To capture the intensity and duration of speeding and tailgating, scaled metrics are developed. These metrics can capture varying levels of aggressive driving behavior enabling, thus, a direct comparison of the various behavioral aspects over time and among different drivers. To identify the effect of HVE and other trip, driver, vehicle or environmental factors on speeding and tailgating, while accounting for possible interrelationship among the behavior-specific scaled metrics, Seeming Unrelated Regression Equation (SURE) models were developed. To analyze the likelihood of occurrence of unsafe lane changes and 'other' aggressive driving behavior types, a grouped random parameters ordered probit model with heterogeneity in means and a correlated grouped random parameters binary logit model were estimated, respectively. The results showed that drivers' awareness of HVE implementation has the potential to decrease aggressive driving behavior patterns, especially unsafe lane changes and 'other' aggressive driving behaviors.

Analysis of stationary and dynamic factors affecting highway accident occurrence: A dynamic correlated grouped random parameters binary logit approach.

Traditional accident analysis typically explores non-time-varying (stationary) factors that affect accident occurrence on roadway segments. However, the impact of time-varying (dynamic) factors is not thoroughly investigated. This paper seeks to simultaneously identify pre-crash stationary and dynamic factors of accident occurrence, while accounting for unobserved heterogeneity. Using highly disaggregate information for the potential dynamic factors, and aggregate data for the traditional stationary elements, a dynamic binary random parameters (mixed) logit framework is employed. With this approach, the dynamic nature of weather-related, and driving- and pavement-condition information is jointly investigated with traditional roadway geometric and traffic characteristics. To additionally account for the combined effect of the dynamic and stationary factors on the accident occurrence, the developed random parameters logit framework allows for possible correlations among the random parameters. The analysis is based on crash and non-crash observations between 2011 and 2013, drawn from urban and rural highway segments in the state of Washington. The findings show that the proposed methodological framework can account for both stationary and dynamic factors affecting accident occurrence probabilities, for panel effects, for unobserved heterogeneity through the use of random parameters, and for possible correlation among the latter. The comparative evaluation among the correlated grouped random parameters, the uncorrelated random parameters logit models, and their fixed parameters logit counterpart, demonstrate the potential of the random parameters modeling, in general, and the benefits of the correlated grouped random parameters approach, specifically, in terms of statistical fit and explanatory power.

Optimal cooperative searching using purely repulsive interactions.

Foraging, either solitarily or collectively, is a necessary behavior for survival that is demonstrated by many organisms. Foraging can be collectively optimized by utilizing communication between the organisms. Examples of such communication range from high level strategic foraging by animal groups to rudimentary signaling among unicellular organisms. Here we systematically study the simplest form of communication via long range repulsive interactions between multiple diffusing Brownian searchers on a one-dimensional lattice. We show that the mean first passage time for any one of them to reach a fixed target depends non-monotonically on the range of the interaction and can be optimized for a repulsive range that is comparable to the average spacing between searchers. Our results suggest that even the most rudimentary form of collective searching does in fact lower the search time for the foragers suggesting robust mechanisms for search optimization in cellular communities.

Does EMS perceived anatomic injury predict trauma center need?

OBJECTIVE: Our objective was to determine the predictive value of the anatomic step of the 2011 Field Triage Decision Scheme for identifying trauma center need. METHODS: Emergency medical services (EMS) providers caring for injured adults transported to regional trauma centers in three midsized communities were interviewed over two years. Patients were included, regardless of injury severity, if they were at least 18 years old and were transported by EMS with a mechanism of injury that was an assault, motor vehicle or motorcycle crash, fall, or pedestrian or bicyclist struck. The interview was conducted upon emergency department (ED) arrival and collected physiologic condition and anatomic injury data. Patients who met the physiologic criteria were excluded. Trauma center need was defined as nonorthopedic surgery within 24 hours, intensive care unit admission, or death prior to hospital discharge. Data were analyzed by calculating descriptive statistics, including positive likelihood ratios (+LRs) with 95% confidence intervals (CIs). RESULTS: A total of 11,892 interviews were conducted. One was excluded because of missing outcome data and 1,274 were excluded because they met the physiologic step. EMS providers identified 1,167 cases that met the anatomic criteria, of which 307 (26%) needed the resources of a trauma center (38% sensitivity, 91% specificity, +LR 4.4; CI: 3.9-4.9). Criteria with a +LR ≥5 were flail chest (9.0; CI: 4.1-19.4), paralysis (6.8; CI: 4.2-11.2), two or more long-bone fractures (6.3; CI: 4.5-8.9), and amputation (6.1; CI: 1.5-24.4). Criteria with a +LR >2 and <5 were penetrating injury (4.8; CI: 4.2-5.6) and skull fracture (4.8; CI: 3.0-7.7). Only pelvic fracture (1.9; CI: 1.3-2.9) had a +LR less than 2. CONCLUSIONS: The anatomic step of the Field Triage Guidelines as determined by EMS providers is a reasonable tool for determining trauma center need. Use of EMS perceived pelvic fracture as an indicator for trauma center need should be reevaluated. Key words: wounds and injury; triage; emergency medical services; emergency medical technicians.

Does mechanism of injury predict trauma center need?

OBJECTIVE: To determine the predictive value of the mechanism-of-injury step of the American College of Surgeons Field Triage Decision Scheme for determining trauma center need. METHODS: Emergency medical services (EMS) providers caring for injured adult patients transported to the regional trauma center in three midsized communities over two years were interviewed upon emergency department (ED) arrival. Included was any injured patient, regardless of injury severity. The interview collected patient physiologic condition, apparent anatomic injury, and mechanism of injury. Using the 1999 Scheme, patients who met the physiologic or anatomic steps were excluded. Patients were considered to need a trauma center if they had nonorthopedic surgery within 24 hours, had intensive care unit admission, or died prior to hospital discharge. Data were analyzed by calculating positive likelihood ratios (+LRs) and 95% confidence intervals (CIs) for each mechanism-of-injury criterion. RESULTS: A total of 11,892 provider interviews were conducted. Of those, one was excluded because outcome data were not available, and 2,408 were excluded because they met the other steps of the Field Triage Decision Scheme. Of the remaining 9,483 cases, 2,363 met one of the mechanism-of-injury criteria, 204 (9%) of whom needed the resources of a trauma center. Criteria with a +LR ≥ 5 were death of another occupant in the same vehicle (6.8; CI: 2.7-16.7), fall >20 feet (5.3; CI: 2.4-11.4), and motor vehicle crash (MVC) extrication time >20 minutes (5.1; CI: 3.2-8.1). Criteria with a +LR between >2 and <5 were intrusion >12 inches (4.2; CI: 2.9-5.9), ejection (3.2; CI: 1.3-8.2), and deformity >20 inches (2.5; CI: 1.9-3.2). The criteria with a +LR ≤ 2 were MVC speed >40 mph (2.0; CI: 1.7-2.4), pedestrian/bicyclist struck at a speed >5 mph (1.2; CI:1.1-1.4), bicyclist/pedestrian thrown or run over (1.2; CI: 0.9-1.6), motorcycle crash at a speed >20 mph (1.2; CI: 1.1-1.4), rider separated from motorcycle (1.0; CI: 0.9-1.2), and MVC rollover (1.0; CI: 0.7-1.5). CONCLUSION: Death of another occupant, fall distance, and extrication time were good predictors of trauma center need when a patient did not meet the anatomic or physiologic conditions. Intrusion, ejection, and vehicle deformity were moderate predictors. Key words: wounds and injury; triage; emergency medical services; emergency medical technicians; predictors; mechanism of injury; trauma center.

EMS Provider assessment of vehicle damage compared with assessment by a professional crash reconstructionist.

OBJECTIVE: To determine the accuracy of emergency medical services (EMS) provider assessments of motor vehicle damage when compared with measurements made by a professional crash reconstructionist. METHODS: EMS providers caring for adult patients injured during a motor vehicle crash and transported to the regional trauma center in a midsized community were interviewed upon emergency department arrival. The interview collected provider estimates of crash mechanism of injury. For crashes that met a preset severity threshold, the vehicle's owner was asked to consent to having a crash reconstructionist assess the vehicle. The assessment included measuring intrusion and external automobile deformity. Vehicle damage was used to calculate change in velocity. Paired t-test, correlation, and kappa were used to compare EMS estimates and investigator-derived values. RESULTS: Ninety-one vehicles were enrolled; of these, 58 were inspected and 33 were excluded because the vehicle was not accessible. Six vehicles had multiple patients. Therefore, a total of 68 EMS estimates were compared with the inspection findings. Patients were 46% male, 28% were admitted to hospital, and 1% died. The mean EMS-estimated deformity was 18 inches and the mean measured deformity was 14 inches. The mean EMS-estimated intrusion was 5 inches and the mean measured intrusion was 4 inches. The EMS providers and the reconstructionist had 68% agreement for determination of external automobile deformity (kappa 0.26) and 88% agreement for determination of intrusion (kappa 0.27) when the 1999 American College of Surgeons Field Triage Decision Scheme criteria were applied. The mean (± standard deviation) EMS-estimated speed prior to the crash was 48 ± 13 mph and the mean reconstructionist-estimated change in velocity was 18 ± 12 mph (correlation -0.45). The EMS providers determined that 19 vehicles had rolled over, whereas the investigator identified 18 (kappa 0.96). In 55 cases, EMS and the investigator agreed on seat belt use; for the remaining 13 cases, there was disagreement (five) or the investigator was unable to make a determination (eight) (kappa 0.40). CONCLUSIONS: This study found that EMS providers are good at estimating rollover. Vehicle intrusion, deformity, and seat belt use appear to be more difficult for EMS to estimate, with only fair agreement with the crash reconstructionist. As expected, the EMS provider -estimated speed prior to the crash does not appear to be a reasonable proxy for change in velocity.

Comparison of the 1999 and 2006 trauma triage guidelines: where do patients go?

BACKGROUND: In 2006, the Centers for Disease Control and Prevention (CDC) released a revised Field Triage Decision Scheme. It is unknown how this modified scheme will affect the number of patients identified by emergency medical services (EMS) for transport to a trauma center. OBJECTIVES: To determine the change in the number of patients transported by EMS who meet the 2006 scheme, compared with the 1999 scheme, and to determine how the scheme change would affect under- and overtriage rates. METHODS: The EMS providers in charge of care for injured adult patients transported to a regional trauma center in three mid-sized cities were interviewed immediately after completing transport. All injured patients were included, regardless of severity. The interview included patient demographics, vital signs, apparent anatomic injury, and the mechanism of injury. Included patients were then followed through hospital discharge. The 1999 and 2006 scheme criteria were each retrospectively applied to the collected data. The numbers of patients identified by the two schemes were determined. Patients were considered to have needed a trauma center if they had nonorthopedic surgery within 24 hours, were admitted to an intensive care unit (ICU), or died. Data were analyzed using descriptive statistics including 95% confidence intervals. RESULTS: EMS interviews were conducted for 11,892 patients and outcome data were unavailable for one patient. The average patient age was 48 years; 51% of the patients were men. Providers reported bringing 54% of the enrolled patients to the trauma center based on their local trauma protocol. Medical record review identified 12% of the enrolled patients as needing a trauma center. Use of the 2006 scheme would have resulted in 1,423 fewer patients (12%; 95% confidence interval [CI]:11%-13%) being identified as needing a trauma center by EMS providers (40%; 95% CI: 39%-41% versus 28%; 95% CI: 27%-29%). Of those patients, 1,344 (94%) did not actually need the resources of a trauma center, whereas 78 (6%) actually needed the resources of a trauma center and would have been undertriaged. CONCLUSION: Use of the 2006 Field Triage Decision Scheme would have resulted in a significant decrease in the number of patients identified as needing the resources of a trauma center. These changes reduced overtriage while causing a small increase in the number of patients who would have been undertriaged.

Optimization of aeromedical base locations in New Mexico using a model that considers crash nodes and paths.

In a recent paper, Tokar Erdemir et al. (2008) introduce models for service systems with service requests originating from both nodes and paths. We demonstrate how to apply and extend their approach to an aeromedical base location application, with specific focus on the state of New Mexico (NM). The current aeromedical base locations of NM are selected without considering motor vehicle crash paths. Crash paths are the roads on which crashes occur, where each road segment has a weight signifying relative crash occurrence. We analyze the loss in accident coverage and location error for current aeromedical base locations. We also provide insights on the relevance of considering crash paths when selecting aeromedical base locations. Additionally, we look briefly at some of the tradeoff issues in locating additional trauma centers vs. additional aeromedical bases in the current aeromedical system of NM. Not surprisingly, tradeoff analysis shows that by locating additional aeromedical bases, we always attain the required coverage level with a lower cost than with locating additional trauma centers.

The effect of unrestrained rear-seat passengers on driver mortality.

BACKGROUND: It is well documented that seat belt usage effectively reduces the severity of motor vehicle occupant injuries and fatalities in roadway crashes. This research examines how the presence of an unrestrained rear-seat passenger seated directly behind an airbag and/or belt-restrained driver affects the driver's risk of injury in two different idealized crash scenarios. Empirical data used in the study was obtained from four sled tests conducted with various size Hybrid III crash test dummies. METHODS: Three tests simulated a frontal (head-on) impact between two vehicles. The first established the baseline condition: a driver dummy restrained by a belt and an airbag system, with an identical belt-restrained dummy seated directly behind. The other two frontal-mode tests involved different size driver dummies restrained in the same manner, with different size unrestrained dummies behind them. A fourth test featured an angled driver-side impact crash with a restrained driver and unrestrained rear seat passenger. RESULTS: In both of the latter cases the driver incurred a high likelihood of severe head and chest injuries relative to that inferred in the baseline exposure. The last test featured two identical dummies in a simulated lateral (driver-side) inter-vehicular impact using a belt-restrained (only) driver and an unrestrained rear-seat passenger. Driver mortality was not significantly affected in this configuration. CONCLUSION: Unrestrained rear-seat passengers place themselves as well as their driver at great risk of serious injury when involved in a head-on crash.

Access to trauma centers in the United States.

CONTEXT: Previous studies have reported that the number and distribution of trauma centers are uneven across states, suggesting large differences in access to trauma center care. OBJECTIVE: To estimate the proportion of US residents having access to trauma centers within 45 and 60 minutes. DESIGN AND SETTING: Cross-sectional study using data from 2 national databases as part of the Trauma Resource Allocation Model for Ambulances and Hospitals (TRAMAH) project. Trauma centers, base helipads, and block group population were counted for all 50 states and the District of Columbia as of January 2005. MAIN OUTCOME MEASURES: Percentages of national, regional, and state populations having access to all 703 level I, II, and III trauma centers in the United States by either ground ambulance or helicopter within 45 and 60 minutes. RESULTS: An estimated 69.2% and 84.1% of all US residents had access to a level I or II trauma center within 45 and 60 minutes, respectively. The 46.7 million Americans who had no access within an hour lived mostly in rural areas, whereas the 42.8 million Americans who had access to 20 or more level I or II trauma centers within an hour lived mostly in urban areas. Within 45 and 60 minutes, respectively, 26.7% and 27.7% of US residents had access to level I or II trauma centers by helicopter only and 1.9% and 3.1% of US residents had access to level I or II centers only from trauma centers or base helipads outside their home states. CONCLUSION: Selecting trauma centers based on geographic need, appropriately locating medical helicopter bases, and establishing formal agreements for sharing trauma care resources across states should be considered to improve access to trauma care in the United States.

Evaluating the reliability of automated collision notification systems.

The use of an automated collision notification (ACN) device in vehicles can greatly reduce the time between crash occurrence and notification of emergency medical services (EMSs). Most ACN devices rely on cellular technology to report important crash information to the proper authorities. The objective of this study was to examine the ability of the existing western New York cellular analog system to support ACN systems. The first task was to develop a model predicting the probability of successfully completing an emergency ACN call at attenuated levels of received signal strength indicator (RSSI), a measurement of the bond between cell phone and tower. Then, empirical estimates were made of the time necessary for call completion at given levels of the RSSI. The RSSI is sampled at locations throughout Erie County, New York, and this information is used to determine the probability of successful call completion for different locations within the county. This model was then applied to historic data for selected past crashes. Finally, the findings were compared with real-world crash data obtained from the ACN Field Operational Test program, where 750 ACN devices were installed in cars and their performance examined over time. An interpolated map of the sampled RSSI values suggests that cellular coverage in Erie County is adequate to support the automated collision network technology. The models and techniques described here are applicable to other areas and regions of the country.