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Public health consequences of road traffic injuries – Estimation of seriously injured persons based on risk for permanent medical impairment
Transportation Research Part F 38 (2016) 1–6
Contents lists available at ScienceDirect
Transportation Research Part F journal homepage: www.elsevier.com/locate/trf
Public health consequences of road traffic injuries – Estimation of seriously injured persons based on risk for permanent medical impairment H.-Y. Berg a,b,⇑, J. Ifver b, M. Hasselberg a a b
Karolinska Institutet, Department of Public Health Sciences, SE 171 77 Stockholm, Sweden Swedish Transport Agency, SE-781 23 Borlänge, Sweden
a r t i c l e
i n f o
Article history: Received 3 February 2015 Received in revised form 23 November 2015 Accepted 14 December 2015
Keywords: Road safety Road injury Swedish traffic accident data acquisition system Medical impairment Injury consequences
a b s t r a c t Despite the fact, that Sweden has one of the safest traffic environments in the world, a large number of people are still injured in road traffic accidents in Sweden. The core concept of the Vision Zero that was adopted by the Swedish parliament in 1997 is to decrease the number of deaths and serious injuries caused by traffic. The vision has been followed-up in terms of decreased mortality, but there was not a consensus on how the concept ‘‘seriously injured” should be measured at that time. The aim of this paper is to describe how to develop a measure to estimate the number of seriously injured people in Sweden. The results show that it is possible to estimate the health impact of road traffic accidents based on the definition of medical impairment. According to the results, 8389 people were seriously injured (permanently medical impaired more then 1%) in the road transport area in Sweden in 2013. If the number of people who had slipped or fallen down without any vehicle being involved is excluded, the number of seriously injured was around 4700. The result of the study has been included in the road safety goal for Sweden with the aim to have 25% less seriously injured people in 2020 than the average for the years 2006–2008. The results also showed that 91% of the seriously injured were transported by car, bike or by foot. The relatively high proportion of pedestrian fall accidents happening within the transport system irrespective of whether a vehicle was moving or not raises the question whether these types of accidents should be included in the reporting of formal road traffic accidents. Ó 2015 Elsevier Ltd. All rights reserved.
1. Introduction Even if Sweden is one of the safest countries in the world as far as road traffic is concerned (IRTAD, 2012), a large number of people are yearly injured in road traffic accidents and major efforts are still needed to continue improving the road safety. One component that is part of the successful development in Sweden is the ‘‘Vision Zero” (Draft Bill 1997:13) that was introduced by the Swedish Parliament in 1997. The core principle of the vision is the value of human life and health and to decrease the number of deaths and serious injuries. A serious injury is defined as ‘‘a physical injury that the victim will not recover from in a reasonable time and might entail lifelong consequences for the person afflicted” (Swedish Road Administration, 2006).
⇑ Corresponding author at: Swedish Transport Agency, Box 267, SE-781 23 Borlänge, Sweden. Tel.: +46 10 49 557 15. E-mail address: [email protected] (H.-Y. Berg). http://dx.doi.org/10.1016/j.trf.2015.12.007 1369-8478/Ó 2015 Elsevier Ltd. All rights reserved.
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H.-Y. Berg et al. / Transportation Research Part F 38 (2016) 1–6
The available documentation describing the health effects of road traffic accidents is well developed in terms of deaths, but it is less so in terms of serious injuries that arise as a result of road traffic accidents. Hospital data reflects the direct and short-term health consequences of an accident, but is often silent regarding the long-term consequences. Police reports include more information about the actual accident and are currently used as the primary means of describing traffic injury development, but statistics based on police assessments of crash sites have limitations. For example, not all accidents are reported to the police, injury classification is broad and uncertain and the long-term consequences of the injury cannot be assessed (Swedish Government, 2006). By this, a combined registry, including information both from the police and from the health care services has been developed and named ‘‘STRADA” (The Swedish Traffic Accident Data Acquisition). The information in STRADA describes the diagnosis and the risk of death of a road traffic injury. An analysis method is however needed to translate the information in STRADA into impact on health. Medical disability is a concept that is used for evaluating various functional impairments, regardless of the reason. The concept has been used since the end of the 20th century in many countries, including Sweden. The concept originates from German private accident insurance (Insurance Sweden, 1996). The concept is used today in individual and collective accident insurance, and is often decisive in terms of the compensation the injured person receives from his/her insurance company. The disability scale is based on functional impairment, e.g. total paralysis is regarded as 100% disability, the loss of one’s hand as 50–65%, and the loss of the outer joint of the ring finger as 2%. When grading the medical disability, it is the functional impairment itself that is decisive, the disability as a consequence of functional impairment is not evaluated. A problem with using medical disability as an outcome measure of severity of an injury is that it is often a long process (sometimes, several years) before a percentage of a medical disability can formally be decided. The Swedish insurance company, Folksam, has been carrying out research for many years into how a diagnosis can be used to forecast the consequences of an injury. The work has focused on defining the probability of certain types of injuries leading to a medical disability (Krafft, 1998; Malm, Krafft, Kullgren, et al., 2008; Norin, Krafft, Korner, Nygren, & Tingvall, 1997). The Folksam method and its ‘‘predictive value” can be used on a sufficiently large group of people to calculate how many people in the group will suffer medical disability at least or above 1% (or 5%, 10% and 30%) as consequence of injury to a part or parts of the body in combination with the assigned AIS value/s. The method is predictive and well suited for use on STRADA data, where tens of thousands of people are allocated an Abbreviated Injury Scale (AAAM, 2015) every year on one or several injured parts of the body. In order to develop ways to capture the public health consequences of road traffic injuries, this methodological paper aims to describe a measure, based on available data sources, on how to estimate the number of seriously injured people in a population. 2. Materials and method A method was developed based on information in the Swedish road traffic accident registry, STRADA and by using the Risk of Permanent Medical Impairment (RPMI) concept (Malm et al., 2008). STRADA includes information from the police (STRADA Police) and from medical centres (STRADA hospital). The database matches accidents known both by the police and the healthcare. In Sweden, a road traffic accident is described as an incident that occurs in traffic on the roads, which involves at least one moving vehicle and results in a personal injury (SIKA, 2008). Information from the health care services provide a better picture of the severity of the injury compared to reports from the police. STRADA receives information about each person injured in traffic from 97% (2013) of the emergency hospitals in Sweden (including AIS-2005 and ICD-10). The Folksam calculations describe the risk of the occurrence of medical disability of a level of 1% or above (5%, 10% and 30%) depending on the parts of the body that have been injured and the AIS values the person has been assigned in the case of injury. This risk of medical disability was taken from an article published in Annuals of Advances in Automotive Medicine 2008 (Malm et al., 2008) and is reported in Table 1. The level of 1% was chosen as a measure of severely injured and used in the calculation of the number of severely injured. Table 1 Risk of Permanent Medical Impairment (RPMI) on 1%+ level (i.e. 1–99%). Numbers in percent. Body region
AIS 1
AIS 2
AIS 3
AIS 4
AIS 5
Head Cervical spine Face Upper extremity Lower extremity and pelvis Thorax Thoracic spine Abdomen Lumbar spine External (skin) and thermal injuries
8.0 16.7 5.8 17.4 17.6 2.6 4.9 0.0 5.7 1.7
15 61 28 35 50 4.0 45 2.4 55 20
50 80 80 85 60 4.0 90 10 70 50
80 100 80 100 60 30 100 20 100 50
100 100 n.a. n.a. 100 30 100 20 100 100
H.-Y. Berg et al. / Transportation Research Part F 38 (2016) 1–6
3
To calculate (Fig. 1 illustrates the general procedure) the number of seriously injured people all reported injuries were taken from STRADA healthcare; 74,111 items from 2013, with each item representing a registered injury. After removing injuries that occurred abroad or outside the road traffic environment (e.g. off-road scooter accidents), 70,896 injuries remained. After removing those who died within 30 days or where the severity or location of the injury was unknown, 69,443 injuries remained. A variable was created that translated each injury into a risk of medical disability, depending on which body region was injured and its AIS level. The database was then aggregated to an individual level so that each item consisted of one patient. This database contained 41,444 subjects with an injury and included information about the injury for each body region that was given the highest AIS value. 3. Results Table 2 reports the most serious injuries of the total sample, divided into body region and AIS value. The most serious injury refers to the injury resulting in the greatest risk of medical disability. Multiplying the figures in Table 2 by the corresponding risk figures in Table 1 gives an estimate of the number of seriously injured people in each group. This process means that only the risk of medical disability from the ‘‘most serious” injury is taken into consideration. A person who has sustained several injuries would naturally run a greater risk of suffering lasting harm. From the 41,444 people who were registered as being injured in 2013, around 35% had received more than one injury. The person who suffered the most injuries had been diagnosed with 25 injuries. In order to calculate the combined risk of lasting harm for each person, the formula 1 Pð1 r i Þ was used in which r i denotes the risk figures in Table 1. The index ‘‘i” represents the body region, and the risk figure is taken from the cell corresponding to the AIS value that the injury has been given. This formula is taken from Folksam Car Model Safety Ratings 2001 (Hägg et al., 2001). If 1 denotes full functional ability, ð1 r i Þ can be interpreted as the probability that full functional ability remains after the most serious injury to body region ‘‘i” has been taken into consideration. If this is multiplied by ð1 r j Þ, it shows the probability that full functional ability remains when also the most serious injury to body region ‘‘j” has been taken into consideration. This process is repeated for the remaining eight body regions. For regions with no injuries (i.e. r i ¼ 0Þ, the factor ð1 ri Þ is equal to 1. When the factors of all body regions are multiplied, the probability of full functional ability for the injured person is obtained. The total risk of lasting harm is finally produced by deducting this value from 1. Using this formula in combination with the number of injured people shown in Table 2 gives the final number of 8119 seriously injured people. However, there are sources of systematic errors. One example is that not all medical units in the country are included in STRADA. In 2013 one major
Fig. 1. A graphical illustration of the calculation procedure.
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H.-Y. Berg et al. / Transportation Research Part F 38 (2016) 1–6
Table 2 Number of injured persons based on their ‘most serious’ injury divided by AIS level and injured body region. STRADA 2013. Body region
AIS 1
AIS 2
AIS 3
AIS 4
Head Cervical spine Face Upper extremity Lower extremity and pelvis Thorax Thoracic spine Abdomen Lumbar spine External (skin) and thermal injuries Total
2048 4962 525 2466 1741 408 254 19 280 14,118 26,821
727 141 265 8155 2941 383 122 51 129 136 13,050
238 48 8 14 750 259 27 30 18 1 1393
67 3 1 11 31 3 11 2 129
AIS 5
AIS 1–5
31 6
3111 5160 798 10,636 5446 1089 409 111 429 14,255 41,444
3 8 3
51
emergency hospital did not register information into STRADA. In order to calculate the total number of persons who were seriously injured in 2013, each cell in Table 3 has to be multiplied by 1/0.9678. The result is shown in Table 3. Table 3 shows that 8389 people are calculated to have been seriously injured in the road transport area in Sweden in 2013. The confidence interval for this number is approx. ±400. If the number of people from the database who belong to a certain group are summarized, this will naturally produce the number of injured people who belong to that group. If the risk of medical disability for each person belonging to the same group is summarized, this will produce an estimate of the number of seriously injured people in the group. If the risk for all people is summarized, this will produce an estimate of the total number of people who are seriously injured. Similarly, it is possible to select group divisions, for example, to receive an estimate of the number of seriously injured people divided into road user category, gender, etc. Table 4 shows that the number of people who have been seriously injured after having travelled in a private car, by bicycle or on foot are in majority. In 2013 1576 people were calculated to have been injured in a private car, while around 3923 pedestrians and 2142 cyclists was calculated to have sustained seriously injuries. The other motorist categories included 246 moped riders and 289 motorcyclists. 132 people who had been seriously injured were injured while travelling in a lorry or bus. Almost ¾ (72%) of those seriously injured had travelled on foot or by bike. Table 4 also shows that 69% of the people in the oldest group were seriously injured in accidents where no moving vehicle was involved. If the number of persons who had slipped or fallen down without any vehicle being involved is removed (3652 in Table 4) from the total sum of 8389 in Tables 3 and 4 (=4737) shows a result of approx. 4700 persons seriously injured by the formal definition of a road traffic accident in Sweden 2013. 4. Discussion The results show that it is possible to calculate the health impact of road traffic accidents based on the consequence of an injury being defined as a medical disability of one percent or more. The Swedish Government (Government’s Draft Bill 2008/2009:93) has decided that the number of seriously injured people in the road transport area should be reduced by a quarter between 2007 and 2020 (from 5400 to 4000). This goal is based on the formal definition of a road transport accident. Today it is obvious that the Governments ambition needs further actions to be fulfilled. The results of this study can then be used for further divided target setting eg. for different road user groups within the road transport sector as well as a following-up measure in Sweden’s efforts to reduce road traffic injuries. One limitation with using this method is that the Folksam’s risk assessment is based both on self-reported injuries and diagnosing by a physician. Most people who report a whiplash injury have not been assessed or diagnosed by a medical
Table 3 Estimated number of seriously injured people divided into AIS level and injured body region 2013. Body region
AIS 1
AIS 2
AIS 3
AIS 4
AIS 5
AIS 1–5
Head Cervical spine Face Upper extremity Lower extremity and pelvis Thorax Thoracic spine Abdomen Lumbar spine External (skin) and thermal injuries Total
235 905 41 463 322 14 16 0 18 248 2260
181 97 94 3028 1534 39 64 3 74 31 5146
152 41 7 12 484 85 25 8 14 1 830
59 3 0 1 9 20 3 6 2 0 103
32 6 0 0 3 6 3 0 0 0 50
659 1052 142 3504 2352 163 111 17 108 280 8389
5
H.-Y. Berg et al. / Transportation Research Part F 38 (2016) 1–6 Table 4 Estimated number of seriously injured people divided into road user category and age group. STRADA 2013. Method of transport
0–17 years
18–24 years
25–64 years
65 years
Total
Pedestrian [fall accidents] Pedestrian [run over] Bicycle Moped Motorbike Private car Other Total
195 34 424 127 5 71 29 884
174 33 157 30 36 419 28 877
1747 107 1203 74 222 923 114 4389
1536 97 359 15 26 162 43 2239
3652 271 2142 246 289 1576 213 8389
doctor and these injuries have been assigned the value 1 on the AIS scale by Folksam. It is possible that the injuries with AIS 1 diagnosed by a physician are more severe than those that are self-reported. If this would be the case, it would mean that the proposed method underestimates the number of seriously injured people. However, the number of people who are seriously injured may need to be adjusted when more reliable information is available. The results of the current study show that most injuries occur among pedestrians and bicyclists (Table 4). The bicyclist are already included in the current definition of a road traffic accident, but ‘‘pedestrian fall accidents” are not included in the current definition of a road traffic accident in Sweden or in Europe. However, the percentage of ‘‘pedestrian fall accidents” is so high that those accidents becomes a very important issue from a health perspective. E.g. during wintertime in Sweden, pedestrians are the category of road users that suffer most injuries, often caused by slippery walkways. Data shows that approximately 85% of pedestrian injuries requiring medical care occurred in urban traffic environment (Öberg & Arvidsson, 2012). The cost for these injuries is also four times higher than the actual winter maintenance cost (Öberg & Arvidsson, 2012). One important aim with the surveillance system STRADA is to emphasize the burden of pedestrian injuries. To further highlight the high burden pedestrian injuries, it must be suggested to define them as road traffic accidents, irrespective of whether a vehicle was moving or not. If they by this are recognized as formal road traffic injuries they will be even more included in the general Swedish effort to increase the level of road safety. One main benefit with the proposed method is that it can be used for benchmarking between different countries. The concept of medical disability is used in more or less the same way in Europe, many countries have access to injury data from hospitals which usually includes ICD-codes. Folksam’s RPMI could potentially be used as a European RPMI and if the ICDcodes are translated into it’s corresponding AIS-value it will then enable comparisons of consequences (defined as medical disability) of injuries between European countries. Another method that can be used to describe the health impact of road traffic accidents are the Function Capacity Index (FCI) (MacKenzie et al., 2002). The Swedish Transport Agency has started to evaluate how a predicted FCI (pFCI) (AAAM, 2008) can be used and the benefit of this is that each person registered in STRADA can be given an index between 1 and 5 depending on the most severe injury according to FCI. Using pFCI will also enable an easier use of STRADA´s plotting module, e.g. when using STRADA for a monthly or yearly follow up of injuries and mapping pFCIs geographically in a local or regional setting. The proposed measure in the current study is summing up risks and need larger groups to give accurate results. Another interesting aspect regarding injury consequences is loss in quality of life caused by a road traffic injury. This aspect will also reflect people’s own perception of how their medical disability affects their quality of life and also potential changes over time. Monitoring individuals’ perception of their quality of life over time after an injury can be of importance for informing both the health care sector and the road transport sector. There are validated measures that can be used for this like EQ-5D (or other HRQoL measures) and by this calculate quality-adjusted life year (QALY) (Krabbe & Weijninen, 2003) or disability-adjusted life year (DALY) (Green & Tones, 2010) which both are measures of disease burden. However, the intent of this study was not to calculate QALY’s or DALY’s but using these measures in relation to the result of this study gives another opportunity to describe the burden of road transport injuries by calculate and visualize the gap between the current situation and the ideal situation without any road transport injuries. 5. Conclusion The current study propose a method that can be used to describe the consequences of road traffic injuries. The method is based on data that is already available in many European countries meaning that it can be used for comparison studies. The high incidence of ‘‘pedestrian fall accidents” indicates the need to include them as road transport accidents irrespective of whether a vehicle was moving or not. References AAAM (2008). Manual abbreviated injury scale 2005 update 2008. In T. A. Gennarelli, E. Wodzin (Eds.), Barrington, IL, USA. AAAM (2015). Association for the Advancement of Automotive Medicine. 2015-01-26.. Ds 1997:13 (1997). På väg mot det trafiksäkra samhället. Government Offices of Sweden, Nordstedts tryckeri 1997.
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Government Bill 2008/09:93. Mål för framtidens resor och transporter. Green, J., & Tones, K. (2010). Health promotion. London: SAGE. ISBN 978-1-84787-489-4. Hägg, A., Krafft, M., Kullgren, A., Nygren, Å., Lie, A., & Tingvall, C. (2001). Folksam Car model safety ratings 2001. Stockholm: Folksam. Insurance Sweden (1996). Gradering av medicinsk invaliditet – 1996. Stockholm. IRTAD (2012). Road safety annual report 2011.. Krabbe, P., & Wiejnen, T. (2003). Guidelines for analysing and reporting EQ-5D outcomes. In R. Brooks, R. Rabin, & F. de Charro (Eds.), The measurement and valuation of health status using EQ-5D: A European perspective. Kluwer Academic Publishers. ISBN 1-4020-1214-4. Krafft, M. (1998). Non-fatal injuries to car occupants. Injury assessment and analysis of impacts causing short- and long term consequences with special reference to neck injuries. Stockholm: Karolinska Institutet. MacKenzie, E. J., Sacco, W. J., Luchter, S., Ditunno, J. F., Forrester Staz, C., Gruen, G. S., ... The Pennsylvania Study Group on Functional Outcomes Following Trauma (2002). Validating the functional capacity index as a measure of outcome following blunt multiple trauma. Quality of Life Research, 11, 797–808. Malm, S., Krafft, M., Kullgren, A., et al (2008). Risk of permanent medical impairment (RPMI) in road traffic accidents. Annuals of Advances in Automotive Medicine. Norin, H., Krafft, M., Korner, J., Nygren, Å., & Tingvall, C. (1997). Injury severity assessment for car occupants in frontal impacts, using disability scaling. Journal of Clinical Epidemiology, 50(1), 95–103. Öberg, G., Arvidsson, A. K. (2012). Injured pedestrians – The cost of pedestrian injuries compared to winter maintenance costs. VTI-report 735. Linköping. SIKA (2008). Vägtrafikskador 2007. SIKA Statistik 2008:27. Swedish Road Administration (2006). SAFE TRAFFIC – vision zero on the move. .
Contents lists available at ScienceDirect
Transportation Research Part F journal homepage: www.elsevier.com/locate/trf
Public health consequences of road traffic injuries – Estimation of seriously injured persons based on risk for permanent medical impairment H.-Y. Berg a,b,⇑, J. Ifver b, M. Hasselberg a a b
Karolinska Institutet, Department of Public Health Sciences, SE 171 77 Stockholm, Sweden Swedish Transport Agency, SE-781 23 Borlänge, Sweden
a r t i c l e
i n f o
Article history: Received 3 February 2015 Received in revised form 23 November 2015 Accepted 14 December 2015
Keywords: Road safety Road injury Swedish traffic accident data acquisition system Medical impairment Injury consequences
a b s t r a c t Despite the fact, that Sweden has one of the safest traffic environments in the world, a large number of people are still injured in road traffic accidents in Sweden. The core concept of the Vision Zero that was adopted by the Swedish parliament in 1997 is to decrease the number of deaths and serious injuries caused by traffic. The vision has been followed-up in terms of decreased mortality, but there was not a consensus on how the concept ‘‘seriously injured” should be measured at that time. The aim of this paper is to describe how to develop a measure to estimate the number of seriously injured people in Sweden. The results show that it is possible to estimate the health impact of road traffic accidents based on the definition of medical impairment. According to the results, 8389 people were seriously injured (permanently medical impaired more then 1%) in the road transport area in Sweden in 2013. If the number of people who had slipped or fallen down without any vehicle being involved is excluded, the number of seriously injured was around 4700. The result of the study has been included in the road safety goal for Sweden with the aim to have 25% less seriously injured people in 2020 than the average for the years 2006–2008. The results also showed that 91% of the seriously injured were transported by car, bike or by foot. The relatively high proportion of pedestrian fall accidents happening within the transport system irrespective of whether a vehicle was moving or not raises the question whether these types of accidents should be included in the reporting of formal road traffic accidents. Ó 2015 Elsevier Ltd. All rights reserved.
1. Introduction Even if Sweden is one of the safest countries in the world as far as road traffic is concerned (IRTAD, 2012), a large number of people are yearly injured in road traffic accidents and major efforts are still needed to continue improving the road safety. One component that is part of the successful development in Sweden is the ‘‘Vision Zero” (Draft Bill 1997:13) that was introduced by the Swedish Parliament in 1997. The core principle of the vision is the value of human life and health and to decrease the number of deaths and serious injuries. A serious injury is defined as ‘‘a physical injury that the victim will not recover from in a reasonable time and might entail lifelong consequences for the person afflicted” (Swedish Road Administration, 2006).
⇑ Corresponding author at: Swedish Transport Agency, Box 267, SE-781 23 Borlänge, Sweden. Tel.: +46 10 49 557 15. E-mail address: [email protected] (H.-Y. Berg). http://dx.doi.org/10.1016/j.trf.2015.12.007 1369-8478/Ó 2015 Elsevier Ltd. All rights reserved.
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H.-Y. Berg et al. / Transportation Research Part F 38 (2016) 1–6
The available documentation describing the health effects of road traffic accidents is well developed in terms of deaths, but it is less so in terms of serious injuries that arise as a result of road traffic accidents. Hospital data reflects the direct and short-term health consequences of an accident, but is often silent regarding the long-term consequences. Police reports include more information about the actual accident and are currently used as the primary means of describing traffic injury development, but statistics based on police assessments of crash sites have limitations. For example, not all accidents are reported to the police, injury classification is broad and uncertain and the long-term consequences of the injury cannot be assessed (Swedish Government, 2006). By this, a combined registry, including information both from the police and from the health care services has been developed and named ‘‘STRADA” (The Swedish Traffic Accident Data Acquisition). The information in STRADA describes the diagnosis and the risk of death of a road traffic injury. An analysis method is however needed to translate the information in STRADA into impact on health. Medical disability is a concept that is used for evaluating various functional impairments, regardless of the reason. The concept has been used since the end of the 20th century in many countries, including Sweden. The concept originates from German private accident insurance (Insurance Sweden, 1996). The concept is used today in individual and collective accident insurance, and is often decisive in terms of the compensation the injured person receives from his/her insurance company. The disability scale is based on functional impairment, e.g. total paralysis is regarded as 100% disability, the loss of one’s hand as 50–65%, and the loss of the outer joint of the ring finger as 2%. When grading the medical disability, it is the functional impairment itself that is decisive, the disability as a consequence of functional impairment is not evaluated. A problem with using medical disability as an outcome measure of severity of an injury is that it is often a long process (sometimes, several years) before a percentage of a medical disability can formally be decided. The Swedish insurance company, Folksam, has been carrying out research for many years into how a diagnosis can be used to forecast the consequences of an injury. The work has focused on defining the probability of certain types of injuries leading to a medical disability (Krafft, 1998; Malm, Krafft, Kullgren, et al., 2008; Norin, Krafft, Korner, Nygren, & Tingvall, 1997). The Folksam method and its ‘‘predictive value” can be used on a sufficiently large group of people to calculate how many people in the group will suffer medical disability at least or above 1% (or 5%, 10% and 30%) as consequence of injury to a part or parts of the body in combination with the assigned AIS value/s. The method is predictive and well suited for use on STRADA data, where tens of thousands of people are allocated an Abbreviated Injury Scale (AAAM, 2015) every year on one or several injured parts of the body. In order to develop ways to capture the public health consequences of road traffic injuries, this methodological paper aims to describe a measure, based on available data sources, on how to estimate the number of seriously injured people in a population. 2. Materials and method A method was developed based on information in the Swedish road traffic accident registry, STRADA and by using the Risk of Permanent Medical Impairment (RPMI) concept (Malm et al., 2008). STRADA includes information from the police (STRADA Police) and from medical centres (STRADA hospital). The database matches accidents known both by the police and the healthcare. In Sweden, a road traffic accident is described as an incident that occurs in traffic on the roads, which involves at least one moving vehicle and results in a personal injury (SIKA, 2008). Information from the health care services provide a better picture of the severity of the injury compared to reports from the police. STRADA receives information about each person injured in traffic from 97% (2013) of the emergency hospitals in Sweden (including AIS-2005 and ICD-10). The Folksam calculations describe the risk of the occurrence of medical disability of a level of 1% or above (5%, 10% and 30%) depending on the parts of the body that have been injured and the AIS values the person has been assigned in the case of injury. This risk of medical disability was taken from an article published in Annuals of Advances in Automotive Medicine 2008 (Malm et al., 2008) and is reported in Table 1. The level of 1% was chosen as a measure of severely injured and used in the calculation of the number of severely injured. Table 1 Risk of Permanent Medical Impairment (RPMI) on 1%+ level (i.e. 1–99%). Numbers in percent. Body region
AIS 1
AIS 2
AIS 3
AIS 4
AIS 5
Head Cervical spine Face Upper extremity Lower extremity and pelvis Thorax Thoracic spine Abdomen Lumbar spine External (skin) and thermal injuries
8.0 16.7 5.8 17.4 17.6 2.6 4.9 0.0 5.7 1.7
15 61 28 35 50 4.0 45 2.4 55 20
50 80 80 85 60 4.0 90 10 70 50
80 100 80 100 60 30 100 20 100 50
100 100 n.a. n.a. 100 30 100 20 100 100
H.-Y. Berg et al. / Transportation Research Part F 38 (2016) 1–6
3
To calculate (Fig. 1 illustrates the general procedure) the number of seriously injured people all reported injuries were taken from STRADA healthcare; 74,111 items from 2013, with each item representing a registered injury. After removing injuries that occurred abroad or outside the road traffic environment (e.g. off-road scooter accidents), 70,896 injuries remained. After removing those who died within 30 days or where the severity or location of the injury was unknown, 69,443 injuries remained. A variable was created that translated each injury into a risk of medical disability, depending on which body region was injured and its AIS level. The database was then aggregated to an individual level so that each item consisted of one patient. This database contained 41,444 subjects with an injury and included information about the injury for each body region that was given the highest AIS value. 3. Results Table 2 reports the most serious injuries of the total sample, divided into body region and AIS value. The most serious injury refers to the injury resulting in the greatest risk of medical disability. Multiplying the figures in Table 2 by the corresponding risk figures in Table 1 gives an estimate of the number of seriously injured people in each group. This process means that only the risk of medical disability from the ‘‘most serious” injury is taken into consideration. A person who has sustained several injuries would naturally run a greater risk of suffering lasting harm. From the 41,444 people who were registered as being injured in 2013, around 35% had received more than one injury. The person who suffered the most injuries had been diagnosed with 25 injuries. In order to calculate the combined risk of lasting harm for each person, the formula 1 Pð1 r i Þ was used in which r i denotes the risk figures in Table 1. The index ‘‘i” represents the body region, and the risk figure is taken from the cell corresponding to the AIS value that the injury has been given. This formula is taken from Folksam Car Model Safety Ratings 2001 (Hägg et al., 2001). If 1 denotes full functional ability, ð1 r i Þ can be interpreted as the probability that full functional ability remains after the most serious injury to body region ‘‘i” has been taken into consideration. If this is multiplied by ð1 r j Þ, it shows the probability that full functional ability remains when also the most serious injury to body region ‘‘j” has been taken into consideration. This process is repeated for the remaining eight body regions. For regions with no injuries (i.e. r i ¼ 0Þ, the factor ð1 ri Þ is equal to 1. When the factors of all body regions are multiplied, the probability of full functional ability for the injured person is obtained. The total risk of lasting harm is finally produced by deducting this value from 1. Using this formula in combination with the number of injured people shown in Table 2 gives the final number of 8119 seriously injured people. However, there are sources of systematic errors. One example is that not all medical units in the country are included in STRADA. In 2013 one major
Fig. 1. A graphical illustration of the calculation procedure.
4
H.-Y. Berg et al. / Transportation Research Part F 38 (2016) 1–6
Table 2 Number of injured persons based on their ‘most serious’ injury divided by AIS level and injured body region. STRADA 2013. Body region
AIS 1
AIS 2
AIS 3
AIS 4
Head Cervical spine Face Upper extremity Lower extremity and pelvis Thorax Thoracic spine Abdomen Lumbar spine External (skin) and thermal injuries Total
2048 4962 525 2466 1741 408 254 19 280 14,118 26,821
727 141 265 8155 2941 383 122 51 129 136 13,050
238 48 8 14 750 259 27 30 18 1 1393
67 3 1 11 31 3 11 2 129
AIS 5
AIS 1–5
31 6
3111 5160 798 10,636 5446 1089 409 111 429 14,255 41,444
3 8 3
51
emergency hospital did not register information into STRADA. In order to calculate the total number of persons who were seriously injured in 2013, each cell in Table 3 has to be multiplied by 1/0.9678. The result is shown in Table 3. Table 3 shows that 8389 people are calculated to have been seriously injured in the road transport area in Sweden in 2013. The confidence interval for this number is approx. ±400. If the number of people from the database who belong to a certain group are summarized, this will naturally produce the number of injured people who belong to that group. If the risk of medical disability for each person belonging to the same group is summarized, this will produce an estimate of the number of seriously injured people in the group. If the risk for all people is summarized, this will produce an estimate of the total number of people who are seriously injured. Similarly, it is possible to select group divisions, for example, to receive an estimate of the number of seriously injured people divided into road user category, gender, etc. Table 4 shows that the number of people who have been seriously injured after having travelled in a private car, by bicycle or on foot are in majority. In 2013 1576 people were calculated to have been injured in a private car, while around 3923 pedestrians and 2142 cyclists was calculated to have sustained seriously injuries. The other motorist categories included 246 moped riders and 289 motorcyclists. 132 people who had been seriously injured were injured while travelling in a lorry or bus. Almost ¾ (72%) of those seriously injured had travelled on foot or by bike. Table 4 also shows that 69% of the people in the oldest group were seriously injured in accidents where no moving vehicle was involved. If the number of persons who had slipped or fallen down without any vehicle being involved is removed (3652 in Table 4) from the total sum of 8389 in Tables 3 and 4 (=4737) shows a result of approx. 4700 persons seriously injured by the formal definition of a road traffic accident in Sweden 2013. 4. Discussion The results show that it is possible to calculate the health impact of road traffic accidents based on the consequence of an injury being defined as a medical disability of one percent or more. The Swedish Government (Government’s Draft Bill 2008/2009:93) has decided that the number of seriously injured people in the road transport area should be reduced by a quarter between 2007 and 2020 (from 5400 to 4000). This goal is based on the formal definition of a road transport accident. Today it is obvious that the Governments ambition needs further actions to be fulfilled. The results of this study can then be used for further divided target setting eg. for different road user groups within the road transport sector as well as a following-up measure in Sweden’s efforts to reduce road traffic injuries. One limitation with using this method is that the Folksam’s risk assessment is based both on self-reported injuries and diagnosing by a physician. Most people who report a whiplash injury have not been assessed or diagnosed by a medical
Table 3 Estimated number of seriously injured people divided into AIS level and injured body region 2013. Body region
AIS 1
AIS 2
AIS 3
AIS 4
AIS 5
AIS 1–5
Head Cervical spine Face Upper extremity Lower extremity and pelvis Thorax Thoracic spine Abdomen Lumbar spine External (skin) and thermal injuries Total
235 905 41 463 322 14 16 0 18 248 2260
181 97 94 3028 1534 39 64 3 74 31 5146
152 41 7 12 484 85 25 8 14 1 830
59 3 0 1 9 20 3 6 2 0 103
32 6 0 0 3 6 3 0 0 0 50
659 1052 142 3504 2352 163 111 17 108 280 8389
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H.-Y. Berg et al. / Transportation Research Part F 38 (2016) 1–6 Table 4 Estimated number of seriously injured people divided into road user category and age group. STRADA 2013. Method of transport
0–17 years
18–24 years
25–64 years
65 years
Total
Pedestrian [fall accidents] Pedestrian [run over] Bicycle Moped Motorbike Private car Other Total
195 34 424 127 5 71 29 884
174 33 157 30 36 419 28 877
1747 107 1203 74 222 923 114 4389
1536 97 359 15 26 162 43 2239
3652 271 2142 246 289 1576 213 8389
doctor and these injuries have been assigned the value 1 on the AIS scale by Folksam. It is possible that the injuries with AIS 1 diagnosed by a physician are more severe than those that are self-reported. If this would be the case, it would mean that the proposed method underestimates the number of seriously injured people. However, the number of people who are seriously injured may need to be adjusted when more reliable information is available. The results of the current study show that most injuries occur among pedestrians and bicyclists (Table 4). The bicyclist are already included in the current definition of a road traffic accident, but ‘‘pedestrian fall accidents” are not included in the current definition of a road traffic accident in Sweden or in Europe. However, the percentage of ‘‘pedestrian fall accidents” is so high that those accidents becomes a very important issue from a health perspective. E.g. during wintertime in Sweden, pedestrians are the category of road users that suffer most injuries, often caused by slippery walkways. Data shows that approximately 85% of pedestrian injuries requiring medical care occurred in urban traffic environment (Öberg & Arvidsson, 2012). The cost for these injuries is also four times higher than the actual winter maintenance cost (Öberg & Arvidsson, 2012). One important aim with the surveillance system STRADA is to emphasize the burden of pedestrian injuries. To further highlight the high burden pedestrian injuries, it must be suggested to define them as road traffic accidents, irrespective of whether a vehicle was moving or not. If they by this are recognized as formal road traffic injuries they will be even more included in the general Swedish effort to increase the level of road safety. One main benefit with the proposed method is that it can be used for benchmarking between different countries. The concept of medical disability is used in more or less the same way in Europe, many countries have access to injury data from hospitals which usually includes ICD-codes. Folksam’s RPMI could potentially be used as a European RPMI and if the ICDcodes are translated into it’s corresponding AIS-value it will then enable comparisons of consequences (defined as medical disability) of injuries between European countries. Another method that can be used to describe the health impact of road traffic accidents are the Function Capacity Index (FCI) (MacKenzie et al., 2002). The Swedish Transport Agency has started to evaluate how a predicted FCI (pFCI) (AAAM, 2008) can be used and the benefit of this is that each person registered in STRADA can be given an index between 1 and 5 depending on the most severe injury according to FCI. Using pFCI will also enable an easier use of STRADA´s plotting module, e.g. when using STRADA for a monthly or yearly follow up of injuries and mapping pFCIs geographically in a local or regional setting. The proposed measure in the current study is summing up risks and need larger groups to give accurate results. Another interesting aspect regarding injury consequences is loss in quality of life caused by a road traffic injury. This aspect will also reflect people’s own perception of how their medical disability affects their quality of life and also potential changes over time. Monitoring individuals’ perception of their quality of life over time after an injury can be of importance for informing both the health care sector and the road transport sector. There are validated measures that can be used for this like EQ-5D (or other HRQoL measures) and by this calculate quality-adjusted life year (QALY) (Krabbe & Weijninen, 2003) or disability-adjusted life year (DALY) (Green & Tones, 2010) which both are measures of disease burden. However, the intent of this study was not to calculate QALY’s or DALY’s but using these measures in relation to the result of this study gives another opportunity to describe the burden of road transport injuries by calculate and visualize the gap between the current situation and the ideal situation without any road transport injuries. 5. Conclusion The current study propose a method that can be used to describe the consequences of road traffic injuries. The method is based on data that is already available in many European countries meaning that it can be used for comparison studies. The high incidence of ‘‘pedestrian fall accidents” indicates the need to include them as road transport accidents irrespective of whether a vehicle was moving or not. References AAAM (2008). Manual abbreviated injury scale 2005 update 2008. In T. A. Gennarelli, E. Wodzin (Eds.), Barrington, IL, USA. AAAM (2015). Association for the Advancement of Automotive Medicine. 2015-01-26.
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Government Bill 2008/09:93. Mål för framtidens resor och transporter. Green, J., & Tones, K. (2010). Health promotion. London: SAGE. ISBN 978-1-84787-489-4. Hägg, A., Krafft, M., Kullgren, A., Nygren, Å., Lie, A., & Tingvall, C. (2001). Folksam Car model safety ratings 2001. Stockholm: Folksam. Insurance Sweden (1996). Gradering av medicinsk invaliditet – 1996. Stockholm. IRTAD (2012). Road safety annual report 2011.