Despite the road safety measures implemented in the region, there was a higher incidence of seriously injured road users in 2014 than in 2003, both in rural and urban areas, but the incidence has increased substantially more in urban areas. These findings correspond to the road safety measures implemented in the region, since fewer measures were implemented in urban areas.
Decreased and increased incidence for car occupants on rural roads
During the study period, the incidence of injuries among car occupants on rural roads decreased on national roads by 26.5% but increased on regional roads by 55.0%. The decrease on national roads occurred despite the fact that national roads are responsible for 69% of transports on rural roads (Table 1). However, given that most road safety measures have been implemented on national roads, it is likely that these measures have prevented injuries for car occupants on these roads. In the region, 88.4% of the length of national roads was transformed by median barriers, speed cameras and speed revisions (Table 1). Previous Swedish studies also indicate a preventive effect of roads rebuilt with median barriers and speed cameras. In a study about effects of rebuilt roads, there was evidence for a 50–60% decrease in number of fatalities and seriously injured road users [28-29]. When speed cameras were introduced in Sweden, it was estimated that they would reduce fatalities and serious injuries by 25% [30]. Several studies have been made globally about the effects of speed cameras, but they vary with location and mode of use [31]. On the other hand, fewer road safety measures were implemented on regional roads, where 16% of the length was transformed by speed reductions of 10 km/h [32]. The limited road safety measures implemented on regional roads may have contributed to the increase of seriously injured car occupants found in this study. A study about road safety effects of speed revision in Sweden reports that the number of seriously injured road users was basically unchanged on rural roads [33]. Thus, the reduced speed limits may not have been effective enough to reduce the number of seriously injured car occupants on regional roads.
Another explanation of the increased incidence on regional roads is that this increase may reflect an increase in road traffic. During the study period, vehicle kilometres on Swedish roads increased by 8.9%, but most of the increase in number of vehicle kilometres took place before the speed revision of 2009 [34]. There is also a study that reports higher fatality and serious injury rates on rural roads with low traffic density (< 2000 vehicles per day) than on roads with a higher density [35].
Increased incidence for unprotected road users in urban areas
In urban areas, although the incidence for car occupants decreased between 2003 and 2014, the incidence for unprotected road users doubled during the study period, though more on tracks and pavements than on roads. Road safety measures in urban areas consisted of building bumps and roundabouts, and making speed limit revisions from 50 to 40 km/h or even to 30 km/h. The implementation of 30 and 40 km/h varies between municipalities in the region and is still ongoing [14]. Although these road safety measures in urban areas may have contributed to reducing serious injuries among car occupants, it seems that they have not influenced the safety of unprotected road users, given the increased incidence for this group. On the other hand, the increase was particularly strong for serious injuries on tracks and pavements where no road safety measures were conducted during the period. Vision Zero recommends separation between motor traffic and unprotected road users [11, 36], but still the incidence has increased more beside the road than on the road. One cause may be an increase in active mobility in RV. Nationally the distance walked increased during the period from 2.8 to 3.5 billion km and by bicycle from 1.8 to 2.4 billion km [37].
Of seriously injured cyclists and pedestrians in urban areas in RV 72% and 88% respectively were older than 45 years [38]. Road users injured in Non-Vision Zero Areas were on average 5.4 years older than those injured in Vision Zero areas. Of these, 60% were cyclists and pedestrians mostly in urban areas. An increased number of people are living in urban areas all over the world, and populations are aging as a result of increased life span and the baby-boom generation of 1940s. Many of them are unprotected road users prone to be injured in single crashes [5, 19, 39-40].
Areas transformed by Vision Zero road safety measures
Only about one-fifth of all serious injuries between 2003 and 2014 occurred in Vision Zero areas. Most of them occurred on rural roads where there is evidence of a decreased number of fatalities and serious injuries because of road safety measures such as median barriers and speed cameras.
Nearly all crashes in transformed urban areas took place on roads with a speed limit of 30 km/h. In accordance with the Vision Zero policy, unprotected road users should not be exposed to vehicles at speeds exceeding 30 km/h [11], but there are studies reporting that even this limit can be too high to prevent serious injuries to pedestrians and cyclists in crashes [41–43]. More cyclists than pedestrians are seriously injured in crashes at speeds of <30 km/h [41, 42]. The speed limit 30 km/h was introduced in urban areas as early as 1998, but 40 km/h instead of 50 km/h has only been possible since 2010. Great variations in speed increase the probability of crashes and serious personal injuries [26].
Public health implications
Despite efforts to reduce serious injuries by means of Vision Zero measures, a doubling of their incidence in urban areas occurred over 12 years, with pedestrians and cyclists being particularly affected. In Sweden, as in many other countries, the state promotes active mobility, both for the sake of public health and to contribute to a sustainable lifestyle for society [6]. There are conflicts, especially in urban areas, between the goals of injury prevention and promoting health through more active mobility. In a review of studies about the health impact of increased levels of active mobility, fourteen studies estimated more fatalities and injuries while six studies estimated decreases of fatalities and injuries. The conclusion of the study is that active mobility provides net health benefits overall [44]. The work with implementing road safety policies hopefully aims to increase these benefits. Findings from this study may possible be extrapolated to the seventeen other regions that have a larger central municipality together with a number of smaller municipalities. In the three metropolitan regions in Sweden there are more lanes for cycling on the roads.
Strengths and limitations
The data in this study are analysed using an extended concept of mobility which includes types of injuries receiving less attention in road safety management such as pedestrians in single crashes [45]. The national indicator for seriously injured road users is furthermore a calculated value for seriously injured persons with a disability of 1% or more [46]. To calculate a corresponding value for a municipality or a region implies greater uncertainty than on national level. Instead this study uses a definition of serious injury that is linked to a scale constructed and used to determine outcome of injuries and is nearly identical to the definition recommended by EU and International Transport Forum (MAIS3+) [4, 25, 47]. Different definitions of serious injury may complicate the work with target fulfilment.
STRADA is a new registry and therefore the study uses data only from 2003, when data from health care and police were collected in the same system [48]. Trend analysis handles the variation in values during the period, but some values are extreme cases as the value for car occupants on national roads in 2006 linked to a bus crash. Values for unprotected road users on tracks and pavements 2010 and 2011 are related to unusually long periods of winter weather (Figures 1, 2 and 3) [49]. Data from more regions or a longer period would probably have resulted in more statistical power.
Possible confounders such as changes in the number of vehicles or unprotected road users in the traffic that could have contributed to the decrease of seriously injured car users or the increase of seriously injured unprotected road users are not included in the analysis since such information is not available. The bivariate nature of the comparisons between rural and urban areas and between vision zero areas and non-vision zero areas also limit interpretations since no confounders are controlled for. Further, non-stationarity and autocorrelations were not considered when showing the linear regressions for time series due to a small number of time points (12 time points). This is also a limitation when interpreting the results of this study.