Injured cyclists with focus on single-bicycle crashes and differences in injury severity in Sweden.

While cycling is promoted as a clean, energy-efficient mode of transport generating physical activity, the number of injured cyclists must decrease to achieve traffic safety goals. The extent of the single bicycle crashes (SBCs) and crash causes are rather well studied. This study expands this knowledge by focusing on differences in injury severity. The aim of the study is to investigate the relationship between injury severity and characteristics of the crash and the cyclist with focus on SBCs. Furthermore, injury risk is calculated for different age classes and sexes, as well as for different purposes of the trip. The results are based on injured cyclists in Sweden (N = 105,836) registered in STRADA, 2010-2019, by both the police and accident and emergency departments (A&Es), with a special focus on injury severity reported by the A&Es. Binary logistic regression was applied to analyse how the odds of being severely injured differed for different cyclists and situations. Results from of the National Travel Survey, 2011-2016, were used to study differences in distance travelled with respect to sex, age group and purpose of the trip. Given that the cyclist is injured in an SBC, the results show a higher probability of being severely injured (maximal AIS 3 or more) for cyclists 45 years or older compared to younger cyclists, for males compared to females and for cyclists not wearing a helmet compared to cyclists wearing a helmet. A higher probability for severe injury was also found for crashes occurring during leisure trips compared to work/school trips, crashes occurring during weekdays compared to weekends and crashes at intersections and road stretches compared to pedestrian and cycle paths. Furthermore, the risk of being severely injured in an SBC per km travelled was higher for cyclists aged 45 and older and during a leisure trip.

Medical impairment and road traffic crashes among older drivers in Sweden - A national, population-based, case-control study.

BACKGROUND: Several medical conditions are known to impair sensory, cognitive and motor functions and are associated with road traffic crashes (RTC). For the drivers of today, we lack updated knowledge on how driving-impairing conditions are associated with RTCs, across all driving-impairing conditions in a given population. We aim to determine this among older drivers in Sweden. METHODS: A national, population register-based, matched case-control study comparing acknowledged driving-impairing health conditions among all older drivers (65 years or older) involved in an injurious RTC in the period 2011-2016 (n = 13,701) with those of controls: older drivers not involved in any RTC (n = 26,525) matched to the cases by age, sex and residential area. The medical conditions, extracted from the National Patient Register from 1997 up until date of RTC, were identified based on ICD-10 diagnosis codes and categorized into the 13 groups of medical conditions listed in the Swedish driver's license regulations. Conditional logistic regression was used to estimate crude and adjusted odds ratios (ORs) with 95% confidence intervals. RESULTS: Unadjusted ORs for RTC were increased for all conditions. After taking the other 12 medical conditions into account, the ORs remained significant in 11 out of the 13. A strong association was found for the group "ADHD and autism spectrum disorders" (OR 2.79, CI 1.47-5.30), although with very low prevalence among cases (0.2%). Moderate associations were found for three conditions with a case prevalence between 1.3% and 8.5%: epilepsy and seizure disorders (OR 1.53, CI 1.25-1.89), substance abuse and dependence (OR 1.45, CI 1.29-1.63), psychological diseases and mental disorders (OR 1.28, CI 1.18-1.39) and for one condition with a case prevalence of 14.7%, diabetes (OR 1.28, CI 1.20-1.36). CONCLUSIONS: In Sweden, in the current generation of older drivers, acknowledged driving-impairing medical conditions at the national and European levels remain a concern. After adjustment for one another, all but 2 of the conditions are associated with RTCs albeit to varying degrees and more pronounced in the age group 65-79 compared to 80 or older. To promote and sustain older people's mobility, addressing this issue will require a blend of interventions where, hopefully, technological and infrastructural innovations may help counteracting individual health-related shortcomings.

Injury crashes and the relationship with disease causing excessive daytime sleepiness.

OBJECTIVE: The objective of this study was to understand the relationship between some of the most common diseases that are known to contribute to excessive daytime sleepiness (EDS) and traffic injury crashes. Specific focus was on the relationship between disease and crash type (single-vehicle or multiple-vehicle crash) and between disease and injury severity. METHODS: This registry-based study considered all passenger car drivers involved in a crash in Sweden between 2011 and 2016 who were 40 years or older at the time of the crash (n = 54,090). For each crash-involved driver, selected medical diagnoses registered from 1997 until the day before the crash were extracted from the National Patient Register. The drivers were assigned to 1 of 4 groups, depending on prior diseases: sleep apnea (SA; group 1, n = 2,165), sleep disorders (group 2, n = 724), Parkinson's or epilepsy (group 3, n = 645) and a reference group (group 4, n = 50,556). Logistic regression analysis compared single-vehicle crashes with multiple-vehicle crashes and moderately/severely injured drivers with slightly/uninjured drivers. RESULTS: Drivers with EDS-related diseases (groups 1-3) had higher probability of a single-vehicle crash than a multiple-vehicle crash compared to the reference group. The most sizeable effect was found for Parkinson's/epilepsy with an odds ratio (OR) of 2.5 (confidence interval [CI], 2.1-3.0). For multiple-vehicle crashes, the probability of a moderate/severe injury was higher for drivers with other sleep disorders (OR = 1.5; CI, 1.0-2.2) and Parkinson's/epilepsy (OR = 1.6; CI, 1.1-2.3) compared to the reference group. CONCLUSIONS: This study has made first steps toward understanding the relationship between some of the most common diseases that are known to contribute to EDS and crashes. Having Parkinson's/epilepsy, in particular, elevated the probability of a single-vehicle crash compared to a multiple-vehicle crash. A single-vehicle crash was seen as indicative of causing a crash; thus, having Parkinson's/epilepsy could be interpreted as a risk factor for crash involvement. Having Parkinson's/epilepsy, as well as other sleep disorders, was also related to more severe outcomes in multiple-vehicle crashes, given that a crash occurred. This was not identified in single-vehicle crashes.

Attentional Demand as a Function of Contextual Factors in Different Traffic Scenarios.

OBJECTIVE: To assess the attentional demand of different contextual factors in driving. BACKGROUND: The attentional demand on the driver varies with the situation. One approach for estimating the attentional demand, via spare capacity, is to use visual occlusion. METHOD: Using a 3 × 5 within-subjects design, 33 participants drove in a fixed-base simulator in three scenarios (i.e., urban, rural, and motorway), combined with five fixed occlusion durations (1.0, 1.4, 1.8, 2.2, and 2.6 s). By pressing a microswitch on a finger, the driver initiated each occlusion, which lasted for the same predetermined duration within each trial. Drivers were instructed to occlude their vision as often as possible while still driving safely. RESULTS: Stepwise logistic regression per scenario indicated that the occlusion predictors varied with scenario. In the urban environment, infrastructure-related variables had the biggest influence, whereas the distance to oncoming traffic played a major role on the rural road. On the motorway, occlusion duration and time since the last occlusion were the main determinants. CONCLUSION: Spare capacity is dependent on the scenario, selected speed, and individual factors. This is important for developing workload managers, infrastructural design, and aspects related to transfer of control in automated driving. APPLICATION: Better knowledge of the determinants of spare capacity in the road environment can help improve workload managers, thereby contributing to more efficient and safer interaction with additional tasks.

An analysis of cyclists' speed at combined pedestrian and cycle paths.

Objective: In Sweden, cyclists, pedestrians, and moped riders share the space on combined pedestrian and cycle paths, and their speeds may differ greatly. Both actual speed and speed differences can potentially influence the number of accidents on the shared paths. As a starting point, this article studies the speed component and how cyclists' speed varies at pedestrian and cycle paths depending on the day, week, and year; road user composition; and road design.Methods: Three data sources were used: Existing measurements of cycle speed and flow in 3 different Swedish municipalities, Eskilstuna (1 site, January-December 2015), Linköping (6 sites, 4 weeks in September-October 2015), and Stockholm (10 sites, 1-5 days in August-September 2015); complementary measurements of cycle speed and flow in Linköping (4 sites, 1-10 days in August-September 2016) and Stockholm (1 site, only part of 2 days in August 2016) were also conducted within the project, in addition to roadside observations of bicycle types at the 5 new sites.Results: The average speed of cyclists on the paths varied between 12.5 and 26.5 km/h. As expected, the lower average speeds were found in uphill directions, near intersections, and on paths with high pedestrian flows. The higher speeds were found in downhill directions and on commuter routes. In all, 70%-95% of road users observed on pedestrian and cycle paths were cyclists, and 5%-30% were pedestrians. The most common type of bicycle was a comfort bike, followed by a trekking bike. Electric-assisted bicycles and racer bikes occurred at all sites, with proportions of 1%-10% and 1%-15%, respectively. The 2 sites with the highest proportion of electric-assisted bicycles and racer bicycles also had the highest average speeds. The differences in average speed throughout the day, week, and year could only be assessed at one of the sites. Only small differences were found, with the most noticeable being that the average speed was lower in January and February (13.8 km/h) compared to the rest of the year (15.3-16.1 km/h). The average speed was also lower during daytime (14.7 km/h) than during other parts of the day (15.4-15.8 km/h).Conclusions: The relationship between bicycle type and measured speed was not entirely clear, but the results suggest that paths with higher proportions of electric and racer bicycles have higher average speeds. There also appears to be a connection between average speed and the width of the distribution; that is, the higher the average speed, the wider the speed distribution. More research is needed on how speed levels and speed variance affect accident risk.

Drink drivers' views of a voluntary alcohol interlock programme for drink driving offenders in Sweden.

A permanent alcohol interlock programme was introduced in Sweden in 2012. The programme is voluntary and allows drink driving offenders to keep their driving licenses if they install alcohol interlocks in their vehicles. The duration of the programme is one or two years, depending on the severity of the drink driving offence. This study aims to improve our knowledge of drink drivers' views of the programme, among both participants and those who chose not to participate. These views were collected through paper questionnaires mailed to the drink drivers' residences. Of 1550 questionnaires mailed to participants and 1492 to non-participants, 689 and 408 were completed, for response rates of 45% among participants and 28% among non-participants (excluding returns because of incorrect addresses or because the respondent was deceased). For participants who were employed or had their own business (n = 513), the main reasons for choosing the alcohol interlock were the need to operate a vehicle at work (69.6%, 95% CI: 65.6-73.6%) and to get to/from work (69.4%, 95% CI: 65.4-73.4%). For those not working (n = 153), the main reasons for participating were that the driving license was required to have a social life and meaningful leisure time (79.7%, 95% CI: 73.3-86.2%) and for shopping (65.4%, 95% CI: 57.7-73.0%). For non-participants, the main reasons for not applying were programme costs (64.4%, 95% CI: 59.5-69.3%), being afraid of being considered alcoholics (37.1%, 95% CI: 32.2-42.1%), and doing well without a license (26.5%, 95% CI: 22.0-31.0%). The results also indicate improved health after the drink driving offence. The largest improvement was found in participants in the two-year programme, in which the proportion of respondents who felt good or very good increased by 39.4% (95% CI: 34.2-44.5%) compared to before the drink driving offence.

Comparing motor-vehicle crash risk of EU and US vehicles.

OBJECTIVE: This study examined the hypotheses that passenger vehicles meeting European Union (EU) safety standards have similar crashworthiness to United States (US) -regulated vehicles in the US driving environment, and vice versa. METHODS: The first step involved identifying appropriate databases of US and EU crashes that include in-depth crash information, such as estimation of crash severity using Delta-V and injury outcome based on medical records. The next step was to harmonize variable definitions and sampling criteria so that the EU data could be combined and compared to the US data using the same or equivalent parameters. Logistic regression models of the risk of a Maximum injury according to the Abbreviated Injury Scale of 3 or greater, or fatality (MAIS3+F) in EU-regulated and US-regulated vehicles were constructed. The injury risk predictions of the EU model and the US model were each applied to both the US and EU standard crash populations. Frontal, near-side, and far-side crashes were analyzed together (termed "front/side crashes") and a separate model was developed for rollover crashes. RESULTS: For the front/side model applied to the US standard population, the mean estimated risk for the US-vehicle model is 0.035 (sd = 0.012), and the mean estimated risk for the EU-vehicle model is 0.023 (sd = 0.016). When applied to the EU front/side population, the US model predicted a 0.065 risk (sd = 0.027), and the EU model predicted a 0.052 risk (sd = 0.025). For the rollover model applied to the US standard population, the US model predicted a risk of 0.071 (sd = 0.024), and the EU model predicted 0.128 risk (sd = 0.057). When applied to the EU rollover standard population, the US model predicted a 0.067 risk (sd = 0.024), and the EU model predicted 0.103 risk (sd = 0.040). CONCLUSIONS: The results based on these methods indicate that EU vehicles most likely have a lower risk of MAIS3+F injury in front/side impacts, while US vehicles most likely have a lower risk of MAIS3+F injury in llroovers. These results should be interpreted with an understanding of the uncertainty of the estimates, the study limitations, and our recommendations for further study detailed in the report.

Traffic safety effects of new speed limits in Sweden.

The effects of speed, both positive and negative, make speed a primary target for policy action. Driving speeds affect the risk of being involved in a crash and the injury severity as well as the noise and exhaust emissions. Starting 2008, the Swedish Transport Administration performed a review of the speed limits on the national rural road network. This review resulted in major changes of the speed limits on the rural road network. It was predominantly roads with a low traffic safety standard and unsatisfactory road sides that were selected for reduced speed limits, as well as roads with a good traffic safety record being selected for an increase in speed limits. During 2008 and 2009, speed limit changed on approximately 20,500km of roads, out of which approximately 2700km were assigned an increase, and 17,800km were assigned a reduction in speed limits. The aim of this study is predominantly to describe and analyse the longterm traffic safety effect of increased, as well as, reduced speed limits, but also to analyse the changes in actual driving speeds due to the changed speed limits. Traffic safety effects are investigated by means of a before and after study with control group and the effects on actual mean speeds are measured by a sampling survey in which speed was measured at randomly selected sites before and after the speed limit changes. Results show a reduction in fatalities on rural roads with reduced speed limit from 90 to 80km/h where the number of fatalities decreased by 14 per year, while no significant changes were seen for the seriously injured. On motorways with an increased speed limit to 120km/h, the number of seriously injured increased by about 15 per year, but no significant changes were seen for the number of deaths. The number of seriously injured increased on all types of motorways, but the worst development was seen for narrow motorways (21.5m wide). For 2+1 roads (a continuous three-lane cross-section with alternating passing lanes and the two directions of travel separated by a median barrier) with decreased speed limit from 110 to 100km/h, the seriously injured decreased by about 16 per year. As regards the change of mean speeds, a decrease in speed limit with 10km/h led to a decrease of mean speeds of around 2-3km/h and an increase of the speed limit with 10km/h resulted in an increase of mean speed by 3km/h. In conclusion, the results show that in total about 17 lives per year have been saved on the road network with changed speed limits. For comparison, 397 road users were killed in total during 2008. The number of seriously injured remain in principle unchanged. It should also be noted that the results are obtained for the road network which changed the speed limits during 2008 and 2009, and it is not certain that the results can be generalised to another road network.

Changes in speed distribution: Applying aggregated safety effect models to individual vehicle speeds.

This study investigated the effect of applying two aggregated models (the Power model and the Exponential model) to individual vehicle speeds instead of mean speeds. This is of particular interest when the measure introduced affects different parts of the speed distribution differently. The aim was to examine how the estimated overall risk was affected when assuming the models are valid on an individual vehicle level. Speed data from two applications of speed measurements were used in the study: an evaluation of movable speed cameras and a national evaluation of new speed limits in Sweden. The results showed that when applied on individual vehicle speed level compared with aggregated level, there was essentially no difference between these for the Power model in the case of injury accidents. However, for fatalities the difference was greater, especially for roads with new cameras where those driving fastest reduced their speed the most. For the case with new speed limits, the individual approach estimated a somewhat smaller effect, reflecting that changes in the 15th percentile (P15) were somewhat larger than changes in P85 in this case. For the Exponential model there was also a clear, although small, difference between applying the model to mean speed changes and individual vehicle speed changes when speed cameras were used. This applied both for injury accidents and fatalities. There were also larger effects for the Exponential model than for the Power model, especially for injury accidents. In conclusion, applying the Power or Exponential model to individual vehicle speeds is an alternative that provides reasonable results in relation to the original Power and Exponential models, but more research is needed to clarify the shape of the individual risk curve. It is not surprising that the impact on severe traffic crashes was larger in situations where those driving fastest reduced their speed the most. Further investigations on use of the Power and/or the Exponential model at individual vehicle level would require more data on the individual level from a range of international studies.

Evaluation of new speed limits in Sweden: a sample survey.

OBJECTIVE: The study sought to estimate changes in actual driving speed occurring after new speed limits were introduced in Sweden's rural road network. METHOD: The effects of speed limit changes were estimated for 7 groups of roads of different types and initial speed limits. To study the effects on the entire road network and not only at specific road sites, a sampling survey was conducted in which speed was measured at randomly selected sites before and after the speed limit changes. Systematic sampling was used to select sites that were widely distributed geographically, though the analysis treats the data as if the sites were selected by simple random sampling. The speed of passing vehicles was generally measured using pneumatic tubes stretched across the road. RESULTS: The survey results indicate that the mean car speed increased by 3.5 km/h when the speed limit increased by 10 km/h on motorways and 2 + 1 roads. Reducing the speed limit by 10 km/h on 2 + 1 roads and rural roads with a speed limit of 110 km/h resulted in a 2 km/h decrease in mean speed. On rural roads where the speed limit was lowered from 90 to 80 km/h, the mean speed decreased by 3.3 km/h. These changes are statistically significant. CONCLUSIONS: The present results are in line with previous results indicating an average change in mean speed of approximately 2.5 km/h when the speed limit changes by 10 km/h. The confidence intervals were in most instances fairly small, indicating a sufficiently large number of measurement sites.