Lowering the speed limit from 30 mph to 25 mph in Boston: effects on vehicle speeds.

INTRODUCTION: Effective 9 January 2017, the default speed limit on Boston streets was reduced from 30 mph to 25 mph. This study evaluated the effects of the speed limit reduction on speeds in Boston. METHOD: Vehicle speeds were collected at sites in Boston where the speed limit was lowered, and at control sites in Providence, Rhode Island, where the speed limit remained unchanged, before and after the speed limit change in Boston. A log-linear regression model estimated the change in vehicle speeds associated with the speed limit reduction. Separate logistic regression models estimated changes in the odds of vehicles exceeding 25 mph, 30 mph and 35 mph associated with the lower speed limit. RESULTS: The speed limit reduction was associated with a 0.3 % reduction in mean speeds (p=0.065), and reductions of 2.9%, 8.5% and 29.3 % in the odds of vehicles exceeding 25 mph, 30 mph and 35 mph, respectively. All these reductions were statistically significant. CONCLUSIONS: Local communities should consider lowering speed limits to reduce speeds and improve safety for all road users. The current practice of setting speed limits according to the 85th percentile free-flow speeds, without consideration of other characteristics of the roadway, can be a hurdle for local communities looking to lower speed limits. Updated state laws that allow municipalities to set lower speed limits on urban streets without requiring costly engineering studies can provide flexibility to municipalities to set speed limits that are safe for all road users.

The Impact of Michigan's Partial Repeal of the Universal Motorcycle Helmet Law on Helmet Use, Fatalities, and Head Injuries.

OBJECTIVES: To evaluate the impact of the partial repeal of Michigan's universal motorcycle helmet law on helmet use, fatalities, and head injuries. METHODS: We compared helmet use rates and motorcycle crash fatality risk for the 12 months before and after the April 13, 2012, repeal with a statewide police-reported crash data set. We linked police-reported crashes to injured riders in a statewide trauma registry. We compared head injury before and after the repeal. Regression examined the effect of helmet use on fatality and head injury risk. RESULTS: Helmet use decreased in crash (93.2% vs 70.8%; P < .001) and trauma data (91.1% vs 66.2%; P < .001) after the repeal. Although fatalities did not change overall (3.3% vs 3.2%; P = .87), head injuries (43.4% vs 49.6%; P < .05) and neurosurgical intervention increased (3.7% vs 6.5%; P < .05). Male gender (adjusted odds ratio [AOR] = 1.65), helmet nonuse (AOR = 1.84), alcohol intoxication (AOR = 11.31), intersection crashes (AOR = 1.62), and crashes at higher speed limits (AOR = 1.04) increased fatality risk. Helmet nonuse (AOR = 2.31) and alcohol intoxication (AOR = 2.81) increased odds of head injury. CONCLUSIONS: Michigan's helmet law repeal resulted in a 24% to 27% helmet use decline among riders in crashes and a 14% increase in head injury.

Effects of lowering speed limits on crash severity in Seattle.

INTRODUCTION: Effective November 2016, the default speed limit in Seattle was lowered from 25 to 20 mph on nonarterial streets and from 30 to 25 mph on arterial streets, unless otherwise posted. In the downtown area, signs indicating the new speed limit were installed on arterials when the lower default limit took effect. Outside the downtown, new speed limit signs were installed on some arterials starting in 2018. The study evaluated effects of the speed limit reduction on crash severity in Seattle. METHOD: Police-reported crashes in Seattle and three control cities in Washington before and after the speed limit change were examined. Logistic regression analyses evaluated effects of the speed limit reduction on odds that a crash involved a fatal (K), disabling (A), or evident (B) injury inside and outside Seattle's downtown. Separate analyses were performed for all crashes (except those occurring on interstates and freeways), for crashes on arterials, and for crashes on nonarterial roads. RESULTS: The speed limit reduction was associated with a significant 17.2% reduction in odds of a crash involving KAB injury among all crashes and a 19.9% reduction for crashes on arterials in downtown Seattle. There were smaller reductions outside the downtown (7.4% for all crashes and 10.7% for crashes on arterials), but they were not significant. CONCLUSIONS: Communities should consider lowering speed limits to improve safety for all road users. When doing so, they should not wait too long to modify speed limit signs to remind drivers of the new speed limits to maximize the safety benefits.

Are front crash prevention systems less effective at preventing rear-end crashes where trucks and motorcycles are struck?

OBJECTIVE: Automatic emergency braking (AEB) and forward collision warning (FCW) are effective at preventing rear-end crashes, but they may perform better in some rear-end crash scenarios than others. The goal of this study was to estimate the effects of front crash prevention systems equipped to passenger vehicles in crashes where another passenger vehicle, a medium/heavy truck, or a motorcycle is struck and compare effectiveness by struck vehicle type. METHODS: More than 160,000 two-vehicle rear-end crashes were identified where a passenger vehicle with or without FCW and AEB was the striking vehicle and another passenger vehicle, medium/heavy truck, or motorcycle was the struck vehicle. Poisson regression was used to estimate the effect of front crash prevention by struck vehicle type on rear-end crash rates per registered vehicle year, accounting for the state and year of the crash and the make, model year, class, and engine type of the striking vehicle. RESULTS: Front crash prevention was associated with a 53% reduction in rear-end crash rates when striking another passenger vehicle, which was significantly larger than the reductions of 38% when striking a medium/heavy truck and 41% when striking a motorcycle. Reductions in rear-end injury crash rates when striking a passenger vehicle also were larger than when striking a medium/heavy truck and when striking a motorcycle. DISCUSSION: If all passenger vehicles were equipped with FCW and AEB that were as effective in crashes striking a truck or motorcycle as they are in crashes with another passenger vehicle, over 5,500 additional crashes with medium/heavy trucks and 500 with motorcycles could potentially be prevented annually in the United States above what would be expected from current front crash prevention systems. Extending front crash prevention testing in consumer information programs to include motorcycle and truck targets could encourage auto manufacturers to improve performance in these crash scenarios.

Habits, attitudes, and expectations of regular users of partial driving automation systems.

INTRODUCTION: Little is known about regular users' perceptions of partial (Level 2) automation or how those perceptions affect behind-the-wheel behavior. METHOD: A mixed mode (phone and online) survey explored the habits, expectations, and attitudes among regular users of General Motors Super Cruise (n = 200), Nissan/Infiniti ProPILOT Assist (n = 202), and Tesla Autopilot (n = 202). RESULTS: All three groups reported being more likely to engage in non-driving-related activities while using their systems than while driving unassisted. Super Cruise and Autopilot users especially were more likely to report engaging in activities that involved taking their hands off the wheel or their eyes off the road. Many Super Cruise and Autopilot users also said they could perform secondary (non-driving-related) tasks better and more often while using their systems, while fewer ProPILOT Assist users shared this opinion. Super Cruise users were most likely and ProPILOT Assist users least likely to think that secondary activities were safer to perform while using their systems. While some drivers said they found user safeguards (e.g., attention reminders, lockouts) annoying and tried to circumvent them, most people said they found them helpful and felt safer with them. Large percentages of users (53% Super Cruise, 42% Autopilot and 12% ProPILOT Assist) indicated they were comfortable treating their systems as self-driving. CONCLUSIONS: Some regular users have a poor understanding of their technology's limits. System design appears to contribute to user perceptions and behavior. However, owner populations also differ, which means habits, attitudes, and expectations may not generalize. Most people value user safeguards, but some implementations may not be effective for everyone. PRACTICAL APPLICATIONS: Multifaceted, proactive user-centric safeguards are needed to shape proper behavior and understanding about drivers' roles and responsibilities while using partial driving automation.

The association between passenger-vehicle front-end profiles and pedestrian injury severity in motor vehicle crashes.

INTRODUCTION: Vehicles play an important role in pedestrian injury risk in crashes. This study examined the association between vehicle front-end geometry and the risk of fatal pedestrian injuries in motor vehicle crashes. METHOD: A total of 17,897 police-reported crashes involving a single passenger vehicle and a single pedestrian in seven states were used in the analysis. Front-end profile parameters of vehicles (2,958 vehicle makes, series, and model years) involved in these crashes were measured from vehicle profile photos, including hood leading edge height, bumper lead angle, hood length, hood angle, and windshield angle. We defined a front-end-shape indicator based on the hood leading edge height and bumper lead angle. Logistic regression analysis evaluated the effects of these parameters on the risk that a pedestrian was fatally injured in a single-vehicle crash. RESULTS: Vehicles with tall and blunt, tall and sloped, and medium-height and blunt front ends were associated with significant increases of 43.6%, 45.4%, and 25.6% in pedestrian fatality risk, respectively, when compared with low and sloped front ends. There was a significant 25.1% increase in the risk if a hood was relatively flat as defined in this study. A relatively long hood and a relatively large windshield angle were associated with 5.9% and 10.7% increases in the risk, respectively, but the increases were not significant. CONCLUSIONS: Vehicle front-end profiles that were significantly associated with increased pedestrian fatal injury risk were identified. PRACTICAL APPLICATIONS: Automakers can make vehicles more pedestrian friendly by designing vehicle front ends that are lower and more sloped. The National Highway Traffic Safety Administration (NHTSA) can consider evaluations that account for the growing hood heights and blunt front ends of the vehicle fleet in the New Car Assessment Program or regulation.

The utility of telematics data for estimating the prevalence of driver handheld cellphone use, 2019-2022.

INTRODUCTION: Driver distraction from handheld cellphone use contributes to fatal crashes every year but is underreported in terms of the proportion of crashes attributed to any distraction or cellphone use specifically. Existing methods to estimate the prevalence of cellphone distractions are also limited (e.g., observing drivers stopped at intersections, when crash risk is low). Our study used data from Cambridge Mobile Telematics to estimate the prevalence of drivers' handheld calls and cellphone manipulation while driving, with "cellphone motion" based on movement recorded by the phones' gyroscopes used as a surrogate for manipulation. METHOD: We compared the telematics measures with the National Highway Traffic Safety Administration's roadside observations of driver electronic device use, and logistic regression tested relationships between regional, legislative, and temporal factors and the odds of cellphone behaviors occurring on a trip or at a given point in time. RESULTS: Results showed 3.5% of trips included at least one handheld phone call and 33.3% included at least an instance of cellphone motion, with handheld calls occurring during 0.78% of overall trip duration and cellphone motion during 2.4% of trip duration. CONCLUSIONS: Correspondence between trends in cellphone distractions across regional, legislative, and temporal factors suggest telematics data have considerable utility and appear to complement existing datasets.

Consumer experiences with crash avoidance feature repairs.

INTRODUCTION: Popularity of crash avoidance features is growing, but so too is confusion around how to repair them, how much repairs should cost, and who should pay for those repairs. This study's purpose was to capture how these issues are affecting consumers. METHOD: A total of 496 vehicle owners in the United States were surveyed online and by phone about their experiences repairing front crash prevention (n = 359), blind spot detection (n = 317), and/or driver assistance cameras (n = 348) equipped on their personal vehicles. RESULTS: Owners tended to have multiple reasons for repairs. Repairs due to vehicle (i.e., crash or windshield) damage corresponded with the greatest likelihood of post-repair issues, especially if calibration was performed, and higher out-of-pocket costs (possibly because of deductibles or other repair work). About half of respondents who had calibrations performed on features repaired because of vehicle damage reported persisting issues with the features after repair. Post-repair issues were more common for repairs performed at independent repairers than dealership service centers, yet similar feature calibration rates were reported for both types of repairers. More people went to dealership service centers than independent repairers, and these respondents were more likely to say they would return to this type of facility for a similar repair in the future. Although most repairers explained why repairs occurred, less than half of respondents said they completely understood the reasons given. CONCLUSIONS: There are new complications in the repair cycle affecting consumers. Post-repair issues are more prevalent than previously assumed, regardless of the crash avoidance feature repaired. PRACTICAL APPLICATIONS: Post-repair issues risk undermining consumer acceptance and the safety potential of critical features. Simplifying the repair process and establishing affordable and accessible centralized databases with repair specifications and instructions from the manufacturers would be a start to addressing industry-wide challenges.

Effects of forward collision warning and automatic emergency braking on rear-end crashes involving pickup trucks.

OBJECTIVE: Forward collision warning (FCW) and automatic emergency braking (AEB) have found to be effective on cars, SUVs, and large trucks. The objective of this study was to extend prior work and estimate the effects of FCW and AEB on pickups. METHODS: Rear-end crashes where a pickup with optional FCW or AEB was the striking vehicle were identified in 25 U.S. states during 2017-2020. Quasi-induced exposure was performed with logistic regression to compare rear-end-striking crashes between vehicles with and without the systems relative to being struck in the rear. Rear-end-striking crash rates per registered vehicle year were also compared between equipped and non-equipped pickups with Poisson regression. The association of the systems with severity in the rear-end-striking crashes that occurred was examined with logistic regression. RESULTS: In the quasi-induced exposure analysis, AEB was associated with statistically significant 34% reductions in the risk of a rear-end-striking crash of any severity and with any injuries, and a 76% reduction in the risk of a rear-end-striking crash with serious or fatal injuries (p = 0.09). FCW was associated with statistically significant declines of 22% in the risk of a rear-end-striking crash with any injuries and 71% in the risk of a rear-end-striking crash with serious or fatal injuries, but FCW was not associated with a change in all rear-end-striking crashes. Results were similar in Poisson regression models for all but FCW's effect on all rear-end-striking crashes. The odds that rear-end-striking crashes involving pickups with FCW resulted in any injuries were 26% lower, and serious/fatal injuries were 75% lower, than those involving pickups without the system. AEB was associated with a nonsignificant reduction in the odds of serious/fatal injuries when a rear-end strike occurred and no change in the odds of any injuries. DISCUSSION: Consistent benefits for front crash prevention systems have been demonstrated for a wide range of vehicle types, now including a sample of pickups. Gaps in proposed U.S. regulations should be filled so that AEB is required equipment on all new vehicles.

Changes in speeding on Virginia roads during the beginning of the COVID-19 pandemic.

OBJECTIVE: We investigated changes in the prevalence of speeding during March-June 2020, the beginning of the COVID-19 pandemic, in Virginia. METHODS: Vehicle speed data from 506 permanent speed counter stations around the state collected during March-June 2019 and March-June 2020 were analyzed. RESULTS: Increases in the proportion of vehicles traveling at least 5 mph and 10 mph above the speed limit were greatest on urban interstates and other freeways, during early morning (6:00-8:59 a.m.) and afternoon commuting hours (3:00-5:59 p.m.) on weekdays, and during afternoons (12:00-5:59 p.m.) on weekends. Logistic regression revealed that the risk of speeding by at least 5 mph increased in 2020 by 22% and by at least 10 mph increased 51% after accounting for road type, time of day, day of week, and traffic volume, relative to 2019. DISCUSSION: Future research should continue to identify where and when speeding problems are most severe, and countermeasures should be directed to the roads and time periods with the largest speeding problems.

Effects of a rural speed management pilot program in Bishopville, Maryland, on public opinion and vehicle speeds.

INTRODUCTION: In summer 2021, a speed management pilot program was conducted on a rural two-lane road (MD 367) in Bishopville, Maryland, that combined countermeasures from engineering, enforcement, and communications. The study evaluated public awareness of the program and its effects on speeds. METHOD: Telephone surveys of drivers in Bishopville and neighboring communities, and of drivers in control communities across the state that had no program, were conducted before and after the program started. Vehicle speeds were collected at treatment sites on MD 367 and at control sites before, during, and after the program. Log-linear regression models estimated changes in speeds associated with the program; separate logistic regression models estimated changes in odds of vehicles exceeding the speed limit and exceeding the speed limit by more than 10 mph during and after the program. RESULTS: The percentage of interviewed drivers in Bishopville and neighboring communities who thought speeding was a major problem on MD 367 declined from 31.0% (before) to 6.7% (after). The program was associated with a 9.3% reduction in mean speeds, a 78.3% reduction in odds of exceeding the speed limit by any amount, and a 79.6% reduction in odds of exceeding the speed limit by more than 10 mph. After the program ended, the mean speeds at the MD 367 sites were 1.5% lower than expected had the program not occurred, odds of exceeding the speed limit by any amount was 37.2% lower, and odds of exceeding the speed limit by more than 10 mph was 11.7% higher. CONCLUSIONS: The program was well publicized and reduced speeding, but the effect did not last after the program ended for those traveling at higher-end speeds. PRACTICAL APPLICATIONS: Comprehensive speed management programs that leverage multiple proven strategies, similar to the program in Bishopville, are recommended in other communities to reduce speeding.

Safety potential of crash avoidance features, improved headlights, and V2V-enhanced technologies for older drivers.

INTRODUCTION: Age-related changes and frailty are among the reasons that older drivers are overrepresented in certain crash types. Vehicle safety features that address these crash types may therefore deliver greater safety benefits for older drivers than for other age groups even though they are designed for the general population. METHODS: U.S. crash data from 2016-2019 were used to estimate the proportion of crash involvements and fatal and nonfatal driver injuries for older (70 years old and above) and middle-aged (35-54 years old) drivers from crash scenarios to which current crash avoidance features, improved headlights, and forthcoming vehicle-to-vehicle (V2V)-connected intersection-assistance features could be relevant. Risk ratios were then calculated to determine the relative benefits of each technology for older drivers compared with middle-aged drivers. RESULTS: Combined, these technologies were potentially relevant to 65 % of older driver and 72 % of middle-aged driver fatalities during the study period. Intersection assistance features showed the most promise for older drivers. Such features were potentially relevant to 32 % of older driver crash involvements, 38 % of older driver injuries, and 31 % of older driver fatalities. Intersection assistance features were significantly more likely to be relevant to older driver deaths than middle-aged driver fatalities (RR, 3.52; 95 % CI, 3.33-3.71). CONCLUSIONS: Vehicle technologies have the potential to substantially reduce or mitigate crashes and the injuries that they cause for everyone, but the potential safety impact of each technology varies by driver age because different age groups are over- or underrepresented in specific crash scenarios. PRACTICAL APPLICATIONS: With the older driver population growing, these findings underscore the need to bring intersection assistance technologies to the consumer market. At the same time, everyone stands to benefit from currently available crash avoidance features and improved headlights, so their use should be promoted among all drivers.

Consumer demand for partial driving automation and hands-free driving capability.

INTRODUCTION: It is often assumed that consumers want partial driving automation in their vehicles, yet there has been little research on the topic. Also unclear is what the public's appetite is for hands-free driving capability, automated (auto)-lane-change functionality, and driver monitoring that helps reinforce proper use of these features. METHOD: Through an internet-based survey of a nationally representative sample of 1,010 U.S. adult drivers, this study explored consumer demand for different aspects of partial driving automation. RESULTS: Eighty percent of drivers want to use lane centering, but more prefer versions with a hands-on-wheel requirement (36%) than hands-free (27%). More than half of drivers are comfortable with different driver monitoring strategies, but comfort level is related to perceptions of feeling safer with it given its role in helping drivers use the technology properly. People who prefer hands-free lane centering are the most accepting of other vehicle technologies, including driver monitoring, but some also indicate an intent to misuse these features. The public is somewhat more reluctant to accept auto lane change, with 73% saying they would use it, and more often prefer it to be driver-initiated (45%) than vehicle-initiated (14%). More than three quarters of drivers want auto lane change to have a hands-on-wheel requirement. CONCLUSION: Consumers are interested in partial driving automation, but there is resistance to more sophisticated functionality, especially vehicle-initiated auto lane change, in a vehicle that cannot technically drive itself. PRACTICAL APPLICATIONS: This study confirms the public's appetite for partial driving automation and possible intention for misuse. It is imperative that the technology be designed in ways that deter such misuse. The data suggest that consumer information, including marketing, has a role to play to communicate the purpose and safety value of driver monitoring and other user-centric design safeguards to promote their implementation, acceptance, and safe adoption.

The association between strengthened cellphone laws and police-reported rear-end crash rates.

INTRODUCTION: Prior evaluations of the connection between cellphone bans and crashes show unclear results. California, Oregon, and Washington enacted legislation (effective in 2017) to update earlier bans specific to handheld conversation and texting. This study evaluated the relationship between the laws and rear-end rates, a crash type sensitive to visual-manual cellphone use, in California, Oregon, and Washington. METHOD: Negative binomial regression compared the change in monthly per capita rear-end crash rates in California, Oregon, and Washington before and after the law changes relative to two control states, Colorado and Idaho, during 2015-2019. Analyses examined (a) rear-end crashes with injuries in all three study states, including minor to fatal injuries; and (b) rear-end crashes of all severities in California and Washington, including property-damage-only crashes and crashes with injuries; Oregon was excluded from this analysis because of a 2018 change to its reporting criteria for property-damage-only crashes. RESULTS: Washington's strengthened law was associated with a significant 7.6% reduction in the rate of monthly rear-end crashes of all severities relative to the controls. Law changes in Oregon and Washington were associated with significant reductions of 8.8% and 10.9%, respectively, in the rates of monthly rear-end crashes with injury relative to the controls. California did not experience changes in rear-end crash rates of all severities or with injuries associated with the strengthened law. CONCLUSION: The results of this study are mixed, with law changes associated with significant reductions in rear-end crash rates in two of the three study states. Differences in the wording of the laws, levels of enforcement, and sanction severity may help explain the divergent results. PRACTICAL APPLICATION: Crash reductions in Oregon and Washington suggest that enacting legislation that comprehensively bans practically all visual-manual cellphone activity may have made the laws easier to enforce and clarified to drivers that handheld cellphone use is unacceptable in these states.

Prevalence of distracted driving by driver characteristics in the United States.

INTRODUCTION: Distracted driving is a long-standing traffic safety concern, though common secondary tasks continually evolve. The goal of this study was to measure the prevalence of self-reported distracted driving behaviors, including activities made possible in recent years by smartphones. METHODS: We conducted a nationwide survey of 2,013 U.S. licensed drivers (ages 16 +). We created four aggregate distraction categories from 18 individual secondary tasks to estimate the proportion of drivers study-wide and by demographic characteristics belonging to each category, defined as those who regularly did (during most or all drives in the previous 30 days) one or more secondary task within each category. Logistic regression estimated the adjusted odds of drivers belonging to each aggregate distraction category by demographic characteristics. RESULTS: Sixty-five percent of drivers reported doing at least one of the 18 secondary tasks regularly, and half did at least one device-based task regularly in the past 30 days. Non-device task prevalence trended downward with age, while device-based task prevalence was consistent among younger drivers before declining beginning with age 35. Males (OR, 1.53; 95% CI, 1.16, 2.02), parents of children ages 18 and younger (OR, 1.47; 95% CI, 1.10, 1.96), and participants who drive in the gig economy (OR, 3.85; 95% CI, 2.73, 5.43) had higher adjusted odds of engaging in "modern" device-based distractions enabled by smartphones (e.g., making video calls, watching videos, using social media) than other drivers. Many drivers are using hands-free capabilities when available for tasks, but for some tasks more than others. CONCLUSIONS: Regular distracted driving is widespread with most behavior concentrated among drivers younger than age 50, though no age group or other demographic studied abstains. PRACTICAL APPLICATIONS: Stakeholders can use these findings to develop countermeasures for distracted driving by targeting specific secondary tasks and the demographics most likely to report regularly doing them.

Effects of automatic emergency braking systems on pedestrian crash risk.

OBJECTIVE: Automatic emergency braking (AEB) that detects pedestrians has great potential to reduce pedestrian crashes. The objective of this study was to examine its effects on real-world police-reported crashes. METHODS: Two methods were used to assess the effects of pedestrian-detecting AEB on pedestrian crash risk. Vehicles with and without the system were examined on models where it was an optional feature. Poisson regression was used to estimate the effects of AEB on pedestrian crash rates per insured vehicle year, and quasi-induced exposure using logistic regression compared involvement in pedestrian crashes to a system-irrelevant crash type. RESULTS: AEB with pedestrian detection was associated with significant reductions of 25%-27% in pedestrian crash risk and 29%-30% in pedestrian injury crash risk. However, there was not evidence that that the system was effective in dark conditions without street lighting, at speed limits of 50 mph or greater, or while the AEB-equipped vehicle was turning. CONCLUSIONS: Pedestrian-detecting AEB is reducing pedestrian crashes, but its effectiveness could be even greater. For the system to make meaningful reductions in pedestrian fatalities, it is crucial for it to work well in dark and high-speed conditions. Other proven interventions to reduce pedestrian crashes under challenging circumstances, such as improved headlights and roadway-based countermeasures, should continue to be implemented in conjunction with use of AEB to prevent pedestrian crashes most effectively.

Safety effects of roundabout conversions in Carmel, Indiana, the Roundabout City.

INTRODUCTION: Roundabouts are a proven safety countermeasure for intersection safety. This study examined the safety effects of roundabout conversions in Carmel, Indiana, also known as the "Roundabout City." Doing so is of particular interest because Carmel has a high density of roundabouts and its drivers understand their effectiveness and are familiar with navigating them. This study also adds to the current state of knowledge about innovative double-teardrop roundabouts (i.e., linked roundabouts with teardrop-shaped central islands). METHOD: Negative binomial models accounting for correlation within site pairs were applied to evaluate the safety effects of converting conventional intersections to roundabouts on total crashes, injury crashes, and property-damage-only (PDO) crashes between study sites and control sites for different roundabout types (single-lane, multi-lane, and double-teardrop). We compared crash data from a 2-year period before the installation of the roundabouts with the 2-year period after the conversions. RESULTS: Injury crashes were 47% lower than what would have been expected without the roundabout conversions. The effects were strongest at the double-teardrop roundabouts, where injury crashes were significantly reduced by 84% and total crashes by 63%. Single-lane roundabouts experienced significant decreases of 51% in total crashes and 50% in PDO crashes (and a nonsignificant decrease of 50% in injury crashes). Multi-lane roundabouts were associated with increases in total and PDO crashes but a 15% decrease in injury crashes, though all were nonsignificant. CONCLUSIONS: Overall, the City of Carmel's roundabout program is associated with reductions in injury crashes, which indicates improvements to safety. Single-lane and double-teardrop roundabouts are associated with improvements in the occurrence and severity of crashes. PRACTICAL APPLICATIONS: Double-teardrop roundabouts should be considered for installation at interchange terminals to improve highway safety.

Relationship of pedestrian crash types and passenger vehicle types.

INTRODUCTION: This is the first known study that examines the association between common pedestrian crash types and passenger vehicle types. METHOD: The analysis included single-vehicle, single-pedestrian crashes from two data sets: North Carolina state crash data and the Fatality Analysis Reporting System (FARS). We performed separate multinomial logistic regression analyses of major pedestrian crash types occurring at or near intersections and at nonintersections. RESULTS: At or near intersections, minivans, large vans, pickups, and SUVs (collectively known as light truck vehicles, or LTVs) were more likely than cars to be involved in crossing-roadway-vehicle-turning-left crashes versus crossing-roadway-vehicle-not-turning crashes. LTVs were also more likely involved in fatal crossing-roadway-vehicle-turning-right crashes at or near intersections versus crossing-roadway-vehicle-not-turning crashes when compared with cars. At nonintersections, LTVs were associated with increased odds of walking-along-roadway crashes relative to crossing-roadway-vehicle-not-turning crashes when compared with cars. CONCLUSIONS: LTVs were more likely to be involved in certain pedestrian crash types, implying a potentially problematic visibility of pedestrians near the front corners of these vehicles. PRACTICAL APPLICATIONS: More research is needed to examine A-pillar blind zones by vehicle type. If it is found that LTVs have larger blind zones, automakers should consider ways to design the A-pillars of these vehicles to minimize blind zones while maintaining pillar strength. Doing this could improve pedestrian safety around these increasingly popular larger vehicles.

Teen driver crashes potentially preventable by crash avoidance features and teen-driver-specific safety technologies.

INTRODUCTION: Vehicle technologies have the potential to help address the disproportionate crash risk that teen drivers face. While crash avoidance features benefit the general population, several address crash scenarios for which teen drivers are particularly at risk, such as rear-end and lane-drift crashes. Other emerging technologies have been designed for teen drivers by addressing certain crash or injury risk factors associated with risky driving behavior, such as speeding or not wearing a seat belt. METHODS: Using nationwide U.S. crash data from 2016 to 2019, this study examined the maximum potential safety benefits of three currently available crash avoidance features (front crash prevention, lane departure prevention, and blind spot monitoring) and three teen-driver-specific technologies (speeding prevention, extended seatbelt reminders and interlocks, and nighttime curfew violation alerts). RESULTS: Teen-driver-specific features have the largest potential for reducing teen driver injuries and fatalities, followed by lane departure prevention, front crash prevention, and blind spot monitoring; however, altogether these technologies have the potential to prevent 78% of teen driver fatalities, 47% of injured teen drivers, and 41% of crashes involving teen drivers. CONCLUSIONS: Crash avoidance features and teen-driver-specific vehicle technologies appear to address different risk factors and crash scenarios, which emphasizes the importance of utilizing both types of safety features to reduce the crash risk of teen drivers. PRACTICAL APPLICATIONS: Wider acceptance, accessibility, and use of these technologies are needed for their safety potential to be realized. More manufacturers should offer and advertise teen-driver-specific technology suites that integrate crash avoidance systems and safety features that address risky driving behavior. While this study shows the maximum potential safety benefits of these technologies, further research is needed to understand the behavioral implications as teens learn to drive with these features.

Older driver vehicle preferences and perceptions of safety: A survey.

INTRODUCTION: Older adults drive older vehicles despite the safety benefits of newer, more crashworthy vehicles. We aimed to build upon previous research and assess vehicle preferences, buying and ownership patterns, and perceptions of safety among older drivers compared with middle-aged drivers. METHODS: Mixed-mode telephone and online panel surveys were conducted with a nationally representative sample of drivers ages 35-54 and 70 and older. Participants were interviewed about their primary vehicle and the characteristics they deemed important at purchase, along with general attitudes surrounding vehicle safety. RESULTS: Fifty-eight percent of drivers ages 70-79 and 63% of drivers 80 and older reported keeping a vehicle on average for 7 years or more before replacing it, compared with 32% of drivers 35-54. At purchase, older drivers were less likely than middle-aged drivers to have insisted upon safety technologies and were less likely to consider safety ratings; 10% of drivers 80 and older and 9% of those 70-79 indicated ratings were not at all important, compared with 4% of those ages 35-54. Among drivers 70 and older, driving patterns and income were strongly associated with vehicle age and type of vehicle driven. CONCLUSIONS: Older drivers place lower importance on vehicle safety and are less likely to seek safety features at purchase than middle-aged drivers. Compounding this, drivers 70 and older who do not drive frequently or who associate low mileage with vehicle safety are less likely to replace their older, low-mileage vehicles. PRACTICAL APPLICATION: Increasing older drivers' understanding of the importance of advancements in vehicle safety may result in greater ownership of safer vehicles and fewer road injuries.