Motorcycle Crashes into Traffic Barriers: Factors Related to Serious and Fatal Injuries (2022)

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104 In-Depth Investigation of Injury Mechanisms in Motorcycle-to- Barrier Crashes 10.1 Objective In the previous chapters, motorcycle-to-barrier collisions in the United States were charac- terized through retrospective studies. However, these studies do not directly answer the ques- tion of how motorcyclists are injured in collisions with traffic barrier. This chapter describes a study developed to determine injury mechanisms through in-depth investigations of motorcycle crashes. This chapter also presents an analysis of injuries in these crashes to identify specific injury mechanisms in motorcycle-to-barrier crashes. The objective of this chapter is to present the results of a series of in-depth motorcycle crash investigations of the injury mechanisms in motorcycle-barrier collisions through clinical studies and crash investigations. 10.2 Methods 10.2.1 Identification of Cases Cases in this study were identified and enrolled by the Wake Forest Baptist Medical Center (Winston-Salem, NC) from patients involved in motorcycle crashes who were admitted to their Level 1 trauma center. Wake Forest is part of the CIREN. Through this network, Wake Forest has established a screening system to identify potential candidates to be incorporated in the CIREN database. Wake Forest expanded their screening system to identify cases for this research. Inclusion criteria were: • SV motorcycle crash; • Collision with guardrail, concrete barrier, or cable barrier; and • Admission to Level 1 trauma center. These inclusion criteria are similar to those from previous chapters. Cases were limited to SV crashes as the focus of this study is on injuries resulting from barrier crashes, not from collisions with other vehicles. In a MV crash, it is difficult to discern which injuries are caused by barriers or other vehicles. Additionally, only cases with barriers in the median or on the roadside were included. If a patient entered the trauma center for injuries in a motorcycle-to-barrier crash matching these criteria, he/she was asked to participate in the study. Consent was obtained before the investigation, and patients who did not consent were not included in the study. 10.2.2 Crash Investigation There were three main components of each crash investigation in this study: (1) environment and barrier, (2) motorcycle, and (3) rider. An investigator visited the crash site soon after the C H A P T E R 1 0

In-Depth Investigation of Injury Mechanisms in Motorcycle-to-Barrier Crashes 105   crash to collect the environmental data elements. Additionally, the investigator inspected the motorcycle and recorded the damage to the vehicle. When possible, the investigator visited the site within a week of the crash. Due to this short time frame, there would typically still be evidence of the crash remaining (e.g., skid marks, fabric transfers, etc.) at the scene. Both the site and the motorcycle were photographed, with particular attention paid to factors associated with the crash, such as fabric transfers, blood, scrapes, or skid marks. Detailed injury data was also gathered from medical records for each patient in the study. WFU tabulated all injuries and assigned an injury score using the AIS. They also provided the imagery for each injury, including CT scans, x-ray images, and patient photos showing external injuries. Additionally, WFU developed 3-D reconstructions for several severe injuries, a useful tool for visualizing the nature of these injuries. If available, photographs of the helmet were taken as evidence of what happened to the motorcyclist’s head during the crash. Lastly, the Wake Forest team interviewed each rider. These interviews provided background about the rider’s driving and motorcycling history, as well as what the rider remembered from the crash. Information about motorcycle training and education was also incorporated since the benefits of rider training are debated (Daniello, Gabler and Mehta 2009). Additionally, information about personal protective gear usage was gathered through the interview. 10.2.3 Case Review The team at Virginia Tech next combined evidence from the crash investigations with the injury data from the patient and reconstructed a description of each crash (Figure 10-1). For these reconstructions, we reviewed the evidence from the scene, motorcycle, helmet, and injuries and determined potential crash scenarios. These scenarios focused on how each injury could have been incurred. Crash causation was discussed in the case reviews, but was not a focus of these reconstructions, as the main goal was to determine injury mechanisms given that a crash had occurred. After thorough review of the case, the team determined the most likely crash scenario based on all the evidence provided on the crash and injuries. From this reconstruction, the team at Virginia Tech determined the injury contact source (ICS) for each injury. The ICS is the impact point that caused the injury (e.g., ground, guardrail post, motorcycle handlebar, etc.). We typically identified ICS based on markings or transfers, Admission to Level 1 Trauma Center Injury Reconstruction Motorcycle Inspection Injury Records Site Inspection Wake Forest Virginia Tech Conducted by: Figure 10-1. Crash Reconstruction Methodology.

106 Motorcycle Crashes into Traffic Barriers: Factors Related to Serious and Fatal Injuries injury patterns, or damage to either the motorcycle or environment. Each ICS was assigned a “Certainty” value, representing how confident the team was in determining the ICS. The certainty values were either “Certain,” “Probable,” or “Possible” with “Possible” being the lowest level and “Certain” being the greatest level of confidence. The ICS and confidence values were developed based on the BioTab methodology developed for the CIREN database (Schneider et al. 2011). 10.2.4 Example Crash Descriptions As an example of the methodology, two of the crashes and the ICS for the most serious inju- ries are described. Contact points for the most severe injuries are included in the descriptions. A summary of all crashes is provided in the Results section of this chapter. Additional details on each crash, the barrier, the rider, and associated injuries are included in the appendices. Cases MC-001-D and MC-001-P This first case involved a male operator and a female passenger traveling on a 2006 Harley- Davidson Electra Glide Ultra Classic Touring motorcycle. Both the 58-year-old operator and the 61-year-old passenger were wearing DOT-approved half-helmets. The motorcycle was traveling in a southwesterly direction on a two-lane rural roadway, and negotiating an “S” curve on a downhill slope. The roadway was bordered to the north by a W-beam guardrail, and to the south by steep hill banks. It was daylight, with no adverse weather conditions, and the roadway was dry. On exiting the left curve segment into the straight away, the operator leaned the motorcycle left, and allowed the left crash bar/foot peg to contact the asphalt pavement. Subsequent control loss redirected the vehicle toward the right (north) pavement edge. As shown in Figure 10-2, as the vehicle departed the north pavement edge, the right aspect of the front wheel/fender impacted a W-beam guardrail. The impact resulted in moderate damage to the motorcycle. At this point, both riders were ejected and the motorcycle rebounded off the guardrail. The motorcycle re-entered the road, as the left side struck the ground. The vehicle slid along the pavement to final rest (on its left side) in the westbound lane, facing south- east. The helmeted 58-year-old male operator and 61-year-old female passenger were reported by police to have come to rest on the north shoulder near the vehicle’s final rest position. The operator reported paying full attention to driving at the time of the collision. The operator (Case MC-001-D) suffered three AIS-3 injuries to his torso: multiple rib fractures, a spleen laceration with hematoma, and a pneumothorax on the left side. All three of these injuries were postulated to be caused by his torso contacting the ground as he fell from the motorcycle. He also suffered an open mid-shaft radius fracture in his left forearm (AIS-3), thought to be caused by impacting either the handlebar or the guardrail. Lastly, he had a hemo- peritoneum (AIS-3), which was postulated to be caused by his shoulder hitting the guardrail. Each of these injury contact sources were thought to be “Possible.” The passenger (Case MC-001-P) suffered two AIS-3 injuries to her head: a right occipital condyle fracture and a subarachnoid hemorrhage. She also suffered two AIS-3 injuries to her spine: a C7 lamina fracture and a T6 spinal burst fracture with 50% height loss. All of these injuries were postulated to have been caused by her head contacting the ground; her helmet was severely scratched and the face mask was cracked. These contact sources were determined with “Probable” certainty. The guardrail struck during this crash successfully redirected the riders and prevented them from what would have likely been a more severe crash. The guardrail was shielding a steep cliff and retained the operator, passenger, and motorcycle, preventing them from going over the cliff.

In-Depth Investigation of Injury Mechanisms in Motorcycle-to-Barrier Crashes 107   Case MC-007-D is case involved a 33-year-old male wearing a DOT-approved half-helmet. He was riding a 2003 Harley-Davidson Electra Glide Classic. It was dark, with no lighting on the street. e rider was traveling northbound on a four-lane arterial with a continuous le-turn lane. Aer exiting a curve, the rider ran o the road to the right and contacted the W-beam guardrail that was placed at the road edge. As shown in Figure 10-3, the motorcycle was redirected and followed along the guardrail for 78 , where the vehicle came to rest. e rider remained on the motorcycle for approximately half that distance (42 ) and was subsequently ejected from the motorcycle. e right side of the rider was in contact with the rail for an extended period during the crash. Based on damage to the guardrail blockouts and possible skin transfers, the rider’s chest was likely dragged along the tops of the rail and posts during the crash. e rider suered multiple rib fractures on the posterior and anterior side. is injury was coded as an AIS-5 injury. Additionally, he suered multiple other so tissue injuries in his chest and abdomen, including bilateral lung contusions (AIS-4), bilateral hemopneumothoraces with large anterior mediastinal hematoma (AIS-4), liver lacerations (AIS-4), and a small spleen Figure 10-2. Crash diagram for Case MC-001.

108 Motorcycle Crashes into Traffic Barriers: Factors Related to Serious and Fatal Injuries laceration (AIS-2). The “probable” cause of these injuries was multiple impacts to the top of the rail and posts while partially seated on the motorcycle. Two of the blockouts between the posts and the rail were rotated, and a potential skin transfer was observed on one post top. This injury pattern and likely rider position were consistent with the rider being dragged along the rail. 10.3 Results The research program investigated a total of 21 cases involving 22 riders striking roadside barriers. All cases were collected from the WFU catchment area, either in the states of North Carolina or Virginia, and date from 2010 to 2016. Table 10-1 resents the composition of the resulting dataset by crash. As shown in Table 10-1, most collisions were with W-beam barrier (19), the most common form of barrier in the United States. Three (3) cases involved collisions with cable barrier, a barrier type typically installed in the median of divided highways to pre- vent cross-median crashes. Only one case involved concrete barrier, the least common barrier in the United States. Most crashes in the sample (81%) involved either large touring or cruiser motorcycles. Most departures were to the right side of the road (76%). The roadway alignment was almost evenly split between curves (9 of 21) and straight runs (8 of 21). Two cases occurred on entrance ramps. A portion of the WFU catchment area is near the Appalachian Mountains on roadways popular with motorcyclists. Reflecting the nature of this area, in many cases the barrier was intended to shield motorists from a steep drop-off or embankment. As these areas were typically heavily forested, the barrier also was intended to prevent collisions with trees. Table 10-2 describes the riders involved in the investigated crashes. Of the riders included in this study, 18 were male and four were female. As a group, the riders were older than the general population. The average age of the riders was 50.1 years old, with a standard deviation Initial Impact 42' 78' NTS Motorcycle Final Rest Position Rider Final Rest Position Figure 10-3. Crash scenario for Case MC-007.

In-Depth Investigation of Injury Mechanisms in Motorcycle-to-Barrier Crashes 109   of 12.4 years. All riders were helmeted. With the exception of the one passenger in case MC-001, all subjects were the operator of the motorcycle. Injuries varied in severity from maximum AIS (MAIS) = 2 to 5 (median = 3). AIS = 3 cor- responds to serious injury. The ISS varied from ISS = 8 to ISS = 45 (median = 22). A total of 15 of 22 riders had an ISS of 16 or greater, the threshold for major trauma. There were no fatalities in the sample. Figure 10-4 presents the distribution of serious injuries (MAIS 3+) injuries by body region. When a subject suffered multiple AIS 3+ injuries to a single body region, only the highest severity injury was counted in this tabulation. The most common serious injuries were to the thorax and the lower extremities. Together these two body regions accounted for nearly two-thirds of all injuries (60%). Figure 10-5 presents the distribution of contact sources associated with AIS 3+ injuries. Examination of the contact sources showed that most AIS 3+ injuries resulted from impact of the rider with the posts supporting either the W-beam rail or the cable barrier (32%). Ground impacts resulting after a rider was ejected from the motorcycle comprised 27% of all AIS 3+ injury body regions. Guardrail and cable barrier posts are designed to deform upon contact with cars and trucks, but crash site inspection showed that these posts deformed very little under loading from a motorcycle or rider. A substantial number of the AIS 3+ injuries (11%) resulted when riders fell across the top of a barrier system while still seated and were then dragged down the length of the barrier before falling off the bike. Crash site inspection combined with examination of injury extent showed that rider contact with top of the W-beam rail and striking the unprotected tops of the posts resulted in laceration-type injuries to the riders. Case Number Motorcycle Type Barrier Type Road Alignment Side of Road Barrier Shielded MC-001 Touring W-Beam Curve Right Steep drop-off MC-002 Cruiser W-Beam Entrance Ramp Right Embankment MC-003 Touring W-Beam & Cable Straight Median Opposing Traffic MC-004 Cruiser Cable Straight Median Opposing Traffic MC-005 Cruiser W-Beam Straight Right Trees and Stream MC-006 Sport W-Beam Curve Right Embankment and Wooded Area MC-007 Touring W-Beam Straight Right Embankment MC-008 3-Wheel Touring W-Beam Curve Right Steep Cliff MC-009 Sport W-Beam Curve Left Embankment and Wooded Area MC-010 Cruiser W-Beam Curve Right Steep drop-off MC-011 Cruiser W-Beam Curve Right Embankment MC-012 Cruiser W-Beam Straight Right Steep drop-off MC-013 Cruiser Cable Straight Median Opposing Traffic MC-014 Cruiser W-Beam Straight Right House MC-015 Cruiser W-Beam Curve Right Steep drop-off MC-016 Cruiser W-Beam Entrance Ramp Right Embankment MC-017 Motocross W-Beam & Concrete Curve Right Bridge MC-018 Cruiser W-Beam Curve Right Steep drop-off MC-020 Cruiser W-Beam Straight Median Opposing Traffic MC-021 Touring with tri- wheel retrofit W-Beam Straight Right Embankment MC-022 Touring W-Beam Curve Right Embankment Table 10-1. Summary of in-depth crashes investigated.

110 Motorcycle Crashes into Traffic Barriers: Factors Related to Serious and Fatal Injuries Case Number Age Gender MAIS ISS Number of injuries Region of Most Serious Injury MC-001-D 58 Male 3 27 11 Thorax Upper Extremity Abdomen MC-001-P 61 Female 3 27 11 Thorax Spine Head MC-002-D 58 Male 3 22 14 Thorax Upper Extremity MC-003-D 49 Male 2 8 5 Head Lower Extremity MC-004-D 31 Male 5 45 29 Head MC-005-D 51 Female 3 9 4 Lower Extremity MC-006-D 46 Male 3 22 4 Thorax Spine MC-007-D 33 Male 5 45 20 Thorax MC-008-D 63 Male 3 14 7 Lower Extremity MC-009-D 19 Male 4 26 8 Thorax MC-010-D 59 Male 3 10 10 Lower Extremity MC-011-D 74 Male 4 29 16 Head MC-012-D 50 Female 4 25 5 Thorax MC-013-D 53 Male 3 17 12 Lower Extremity MC-014-D 43 Male 2 9 9 Spine Upper Extremity MC-015-D 48 Female 4 29 10 Lower Extremity MC-016-D 67 Male 3 17 9 Lower Extremity MC-017-D 39 Male 3 11 10 Upper Extremity MC-018-D 43 Male 3 10 8 Lower Extremity MC-020-D 52 Male 5 38 29 Head MC-021-D 55 Male 3 22 15 Thorax MC-022-D 51 Male 3 17 12 Head Table 10-2. Summary of rider demographics and injuries. 3% 8% 8% 8% 14% 30% 30% 0% 5% 10% 15% 20% 25% 30% 35% Neck Abdomen Spine Upper Ex Head Lower Ex Thorax Figure 10-4. Distribution of AIS 31 injuries by body region.

In-Depth Investigation of Injury Mechanisms in Motorcycle-to-Barrier Crashes 111   Nearly half of all serious injuries were the result of impact with some component of the barriers; however, the distribution of serious injuries was not uniform across barrier components. Nearly two-thirds of the serious injuries from barrier impact (60%) resulted from contact with the posts. Almost one-quarter of the serious injuries (23%) from barrier impact were caused by being dragged over the tops of the posts, top of the rail, or top cable. The balance was due to blunt impact with the barrier face. 10.3.1 Personal Protective Equipment Personal protective equipment (PPE) may prevent or mitigate motorcyclist injuries in all types of crashes. Table 10-3 presents the distribution of PPE worn by the riders in the WFU motorcycle-barrier dataset. All riders were helmeted. Both North Carolina and Virginia require that riders wear helmets. All helmets were DOT-certified. Only one rider (MC-006-D) was wearing body armor. Half of all riders (11 of 22 riders) wore motorcycle jackets. All jackets and chaps were made of leather unless otherwise noted in Table 10-3. However, with the exception of helmets, none of this PPE is intended to prevent or mitigate impact injury, but rather to prevent or mitigate abrasions from the road surface (i.e., “road rash”). The severity of abrasion injuries would typically not rise to the level of serious injury (AIS 3+). 10.3.2 Human Factors The focus of this research program was on injury mechanisms and injury severity given that a crash has occurred, rather than on factors that may have caused the crash. However, through interviews with the operator and witnesses, our investigations did collect a limited amount of information on the human factors associated with each crash. Table 10-4 presents these human factors for each operator. In general, the operators were older than the U.S. population. The average age of the operators was 49.7 years. The median age of operators was 50 years old. In general, the operators had many years of experience operating motorcycles. The average number of years riding was 18 years. The median number of years riding was 11 years. However, two riders were novices and had only been riding for a few days. Speeding did not appear to be 5% 8% 8% 11% 16% 24% 27% 0% 5% 10% 15% 20% 25% 30% Cable Post Guardrail face Motorcycle Top of Post and Rail Unknown / Other Guardrail Post Ground Figure 10-5. Distribution of AIS 31 injuries by ICS.

112 Motorcycle Crashes into Traffic Barriers: Factors Related to Serious and Fatal Injuries a contributing crash causation factor. Police-estimated travel speed exceeded the posted speed limit in three of the 19 crashes in which the posted speed limit was known. Alcohol involvement was noted in two of the 21 operators. 10.4 Discussion This study is one of the first in the United States to investigate factors leading to serious injury in motorcycle collisions with roadside barriers. This chapter presented the results of a study on the injury mechanisms in motorcycle-to-guardrail collisions. The study investigated 21 serious motorcycle-to-barrier crashes, involving 22 riders. In these crashes, the most common regions to suffer the most serious injury were the head, lower extremities, and thorax. The thorax suffered the greatest number of serious injuries. The extremities suffered the most injuries; however, these tended to be less severe than injuries in other body regions. These findings are consistent with those presented in our Maryland CODES study and the Bambach et al. (2012) study. In most of the crashes investigated, the guardrail prevented the rider from a potentially more hazardous collision with trees. In the earlier discussion on fatality risk, collisions with trees were more likely to be fatal than collisions with guardrail. Additionally, in several of the cases, the guardrail likely prevented the rider from traveling over a cliff or embankment. Case Number MAIS ISS Helmet Face Mask Goggles Jacket* Gloves Chaps* Boots MC-001-D 3 27 ⨉ ⨉ ⨉ ⨉ MC-001-P 3 27 ⨉ ⨉ ⨉ ⨉ MC-002-D 3 22 ⨉ ⨉ MC-003-D 2 8 ⨉ MC-004-D 5 45 ⨉ MC-005-D 3 9 ⨉ ⨉ MC-006-D 3 22 ⨉ ⨉ (1) ⨉ ⨉(1) MC-007-D 5 45 ⨉ MC-008-D 3 14 ⨉ ⨉ ⨉ ⨉ ⨉ MC-009-D 4 26 ⨉ MC-010-D 3 10 ⨉ ⨉ (2) MC-011-D 4 29 ⨉ ⨉ ⨉ MC-012-D 4 25 ⨉ ⨉ ⨉ ⨉ ⨉ ⨉ MC-013-D 3 17 ⨉ ⨉ (3) ⨉ ⨉ ⨉ MC-014-D 2 9 ⨉ MC-015-D 4 29 ⨉ ⨉ MC-016-D 3 17 ⨉ ⨉ ⨉ ⨉ MC-017-D 3 11 ⨉ ⨉ MC-018-D 3 10 ⨉ ⨉ MC-020-D 5 38 ⨉ ⨉ ⨉ MC-021-D 3 22 ⨉ ⨉ MC-022-D 3 17 ⨉ ⨉ ⨉ ⨉ ⨉ ⨉ * Material is leather unless otherwise noted. 1 Jacket made out of Kevlar w/ built-in elbow and shoulder armor; pants made out of Kevlar as opposed to leather chaps. 2 Jacket made out of neoprene. 3 Vest as opposed to a full jacket Table 10-3. Distribution of rider PPE.

In-Depth Investigation of Injury Mechanisms in Motorcycle-to-Barrier Crashes 113   Therefore, though guardrail collisions are severe, removing the barriers is not the solution to the problem. Additionally, all components of the guardrail were associated with injury causation. However, they varied in severity. Nearly two-thirds of the serious injuries thought to be caused by the barrier were postulated to be caused by rider entanglement with the posts supporting the barrier. In approximately one-quarter of the crashes investigated, riders were believed to interact pri- marily with the top of the rail or top cable, as opposed to going under the barrier. Providing a protective covering to the top edge of the rail and the upper faces of the posts may mitigate these injuries. Finally, not all of the recorded injuries were thought to be caused by contact with the barrier. An estimated 27% of serious injuries were believed to be caused by blunt impact with the ground. The study has shown that the primary injury mechanisms in our sample were (1) rider entanglement with posts; (2) lacerations from top of posts, both W-beam and cable barrier; and (3) laceration from the top of W-beam rail. Of note are our observations on cable barrier (i.e., wire-rope barrier) collisions. Despite the concern of laceration injuries to motorcyclists contact- ing wire-rope barriers, we found no evidence of laceration injuries from the wire rope in these systems. Injuries were found in collisions with wire-rope barrier, but the injuries resulted from contact with the posts rather than with the wire rope. This clinical finding is consistent with the conclusions from our bulk accident study conducted using state crash data (Chapter 6), which Case Number Age Gender Toxicology Time Since Departure Riding Experience (years) Police- estimated, Travel Speed (mph) Posted Speed Limit (mph) MC-001-D 58 Male None 30 min. 8 30 55 MC-002-D 58 Male None 25 min. 40 35-40 45 MC-003-D 49 Male Alcohol Use, BAC unknown 40 min. 3 65 65 MC-004-D 31 Male None 30 min. 3 65 65 MC-005-D 51 Female None 1 min. 2 5 35 MC-006-D 46 Male None 8 hr. 7 50* Unknown MC-007-D 33 Male None 30 min. - 55 45 MC-008-D 63 Male None Full day 40 40 55 MC-009-D 19 Male None 30 min. 10 50 55 MC-010-D 59 Male None Unknown Unknown 25 55 MC-011-D 74 Male None Unknown 53 50 55 MC-012-D 50 Female None 2 hr. Unknown Unknown Unknown MC-013-D 53 Male BAC: 0.184 at hospital 5-10 min. Unknown 65 65 MC-014-D 43 Male None 5 min. - 15 55 MC-015-D 48 Female None 8 hr. 13 55 55 MC-016-D 67 Male None Unknown 15 65 55 MC-017-D 39 Male None 5 min. 20 70 55 MC-018-D 43 Male None Unknown 5 40 55 MC-020-D 52 Male None 10 min. 36 55 55 MC-021-D 55 Male None Unknown 35 years 45 45 MC-022-D 51 Male None Unknown Unknown 45 45 *Not police reported. Estimated by rider. Table 10-4. Distribution of operator human factors.

114 Motorcycle Crashes into Traffic Barriers: Factors Related to Serious and Fatal Injuries found no statistically significant difference between the injury risk of W-beam and cable barrier, both systems supported by unprotected posts. This study has important implications for U.S. federal and state transportation agencies seeking ways to reduce the risk of serious-to-fatal injury for motorcyclists. The findings show the need for the adoption of MPS that either pad or shield the posts to prevent motorcyclist entangle- ment. MPS have been implemented in Europe and Australia that have tremendous potential to mitigate injuries in barrier collisions (Corben et al. 2010; La Torre et al. 2012). To date, these systems have not been adopted in the United States. 10.5 Limitations This study has several limitations: (1) the findings are based on a small sample of cases; (2) the findings are based on a convenience sample of cases admitted to a Level 1 trauma center; and (3) the sample was collected from only a single region of the United States. The sample did, however, include all major barrier types encountered in the United States. Even though both states in the catchment area for data collection have mandatory helmet laws, only 20 states in the United States have mandatory helmet laws. The results should not be interpreted as nationally representative of the United States. Rather, the findings should be used as a means to identify opportunities for countermeasure development and the need to prioritize the development and implementation of MPS for barriers.