key: cord-0776565-ho1ggsz4 authors: Saladié, Òscar; Bustamante, Edgar; Gutiérrez, Aaron title: COVID-19 lockdown and reduction of traffic accidents in Tarragona province, Spain date: 2020-09-06 journal: Transportation research interdisciplinary perspectives DOI: 10.1016/j.trip.2020.100218 sha: e0feee03b150fd5ff95327503dc6d72a6920d768 doc_id: 776565 cord_uid: ho1ggsz4 This paper analyses the impact that the lockdown decreed by the Spanish Government to combat COVID-19 has had on traffic accidents in Tarragona province (Spain). The number of traffic accidents registered during the first six weeks of lockdown (March 16–April 26) was compared to those reported in the previous six weeks (February 3–March 15). The number of collisions registered during these two periods was also compared to those registered in the equivalent weeks of 2018–2019. During lockdown, the number of traffic accidents fell by 74% compared to the period before lockdown and by 76% with respect to the equivalent period in 2018–2019. This reduction of accidents has been higher than the decrease of mobility during that period (55%). This suggests a multiplicative positive effect of traffic reduction on roads safety. Our findings provide new evidences of the disruptive effect of the COVID-19 pandemic on transportation and of how it could be used as a catalyst to promote more sustainable and secure transport systems. The year 2020 will be remembered for the COVID-19 pandemic, which has infected several million people (confirmed cases) around the world, causing hundreds of thousands of deaths. Some national governments responded by imposing lockdowns in order to reduce the spread of infection and potential deaths, but this had negative economic and social repercussions (unemployment, business bankruptcies, etc.) (Béland et al., 2020) and raised the question of what the main priority should be: public health or the economy? One of the restrictions introduced limited personal mobility, as air and land traffic were two of the main vectors for Even so, these changes have so far implied only immediate and short-time improvements. When normal activity resumes, old challenges are likely to re-emerge. The State of Alarm decreed by the Spanish Government (BOE, 2020) came into force on March 16th. Citizens throughout the country subsequently had certain of their activities restricted, including their mobility. According to the Spanish Directorate-General for Traffic (DGT, 2020) , during the first six weeks of lockdown, interurban traffic in Spain decreased by 72%, with notable differences between weekdays (-65%) and weekends (-86%). This included a drastic reduction in urban traffic, so the corresponding reduction in traffic accidents was perhaps only to be expected. Taking all of these circumstances into account, our main objective was to analyse the impact that the COVID-19 lockdown had on traffic accidents. Tarragona province (in North-East Spain) was chosen as a study case. The reduction in the number of traffic accidents in the region was analysed, as were more specific details, including their: (1) territorial location, (2) severity, (3) distribution between weekdays and weekends/holidays, and (4) the types of road (urban or interurban, and different types of interurban roads) on which they occurred. This research will contribute new evidence to the growing literature on the multiple effects of the COVID-19 pandemic on transportation around the world. Tarragona is a province of 800,000 inhabitants whose population is predominantly concentrated along the coast and in and around its two main cities ( Figure 1 ): Tarragona (134,000) and Reus (104, 000) . It has no other settlements with over 50,000 inhabitants, and The territory is crossed by several motorways, including the AP7 and AP2 (Figure 1 ). The former follows the coastline, communicating Barcelona and the South of France, to the northeast, with Valence and much of Spain's southern Mediterranean coast area to the southwest. The AP2 connects the AP7 in the east of the province to such cities as Zaragoza and Madrid to the west. The most important conventional basic road in terms of daily traffic intensity is the N340, which runs parallel to the AP7. The section of the AP7 between Tarragona and the Vandellòs nuclear power station was subsequently replaced by a new motorway: the A7. Another important conventional basic road is the N420, which begins in Reus and provides communication with Zaragoza, to the west. It is also relevant to highlight four other major roads that cross the territory from north to south. These are (from east to west): the N240 (a conventional basic road); the A27 (a motorway with the same characteristics as the A7); the C14 (a conventional basic road with a section of dual carriageway); and the C12 (a conventional basic road, often referred to as the Ebro Axis, which runs parallel to the River Ebro), which crosses the southern part of J o u r n a l P r e -p r o o f Tarragona province. Another major roadway is the T11, which is an interurban motorway, running between Tarragona and Reus. The data on traffic accidents were obtained from the Directorate-General of Fire Prevention, Extinction and Rescue (DGPEIS) of the Generalitat de Catalunya (the Autonomous Government of Catalonia) and included information from the Catalan Fire Department. The information was not fully complete because some traffic accidents are only dealt with by the police. Our database did, however, include all the road accidents with the most severe repercussions in terms of material and economic damage, injuries, and fatalities. The dataset covered the period from Monday, February 3, to Sunday, April 26, 2020: a total of 84 days (12 weeks). The first six weeks corresponded to the period immediately before the lockdown (Monday, February 3-Sunday, March 15) and the other six to that after of lockdown (Monday, March 16 -Sunday, April 26). Both 42-day periods included 30 weekdays and six weekends (12 days). The second period included only 28 working days due to the Easter holidays. The DGPEIS also provided data on traffic accidents for the equivalent periods in 2018 (Monday, February 5-Sunday, April 29) and 2019 (Monday, February 4-Sunday, April 28). The distribution of days between weekdays, weekends and holidays was the same as in 2020. We did not, however, receive any information concerning the times of the accidents, the collision speeds, or the numbers and characteristics of the vehicles involved in these accidents. We compared the number of traffic accidents and daily averages both before and after the lockdown in 2020 with those that took place during the equivalent period in 2018-2019, following a similar approach to those used by Aloi et al. (2020) and Shilling and Waetjen (2020) . The chi-square test (χ2) was then applied to analyse whether the differences in the distribution of the traffic accidents were statistically significant. The same analysis was performed for the severity of the accidents and whether they occurred on weekdays or at weekends/holiday, on urban or interurban roads, and according to the typology of the roads on which they took place: motorway, conventional basic road, or secondary road. The distribution of the accidents was correlated with the reduction in mobility in the same area and during the same period. To do this, we used data on daily mobility in Tarragona province that were collected via mobile phone traces and compiled by the Spanish Ministry of Transport, Mobility and Urban Agenda. In that case, the available data for each day took into account the mobility flows for a reference period chosen by the same Ministry (February 14-20) with value 100. Finally, in order to analyse if the lockdown had also implied a different spatial pattern of accident distribution, we used a Kernel Density Estimation function to calculate the concentration of traffic accidents both before and during the lockdown period. This estimation computes a magnitude per unit area, based on point or polyline features, using a kernel function to fit a smoothly tapered surface to each point or polyline. This enabled us to produce a series of heat maps showing the highest and lowest concentrations of accidents in each of the periods studied. Kernel Density Estimation is a well-established technique for A total of 192 traffic accidents involving the intervention of the Catalan Fire Department took place during the 84 days covered by the study (Table 1 ). The daily average was 2.3. The number of traffic accidents registered during these 12 weeks represented a decrease of 34% compared to the average for the equivalent period in 2018-2019. However, it should be underlined that the lockdown began in the middle of the period analysed (on March 16). Table 1 shows the number of traffic accidents and the daily average for the six weeks before lockdown and also for the first six weeks of the lockdown period. The pre-lockdown period was associated with almost four of every five traffic accidents recorded (3.6 per day). The average number of daily traffic accidents during the lockdown period fell to 0.9 and the total number of traffic accidents fell by 74%. These results were consistent with the global reduction in mobility. Figure Reus exhibited very high concentrations of traffic accidents. In addition to their high population densities, both cities also receive a large number of commuters (workers and students), as well as other people visiting them for shopping or leisure purposes. Figure 4 shows the influence of these two motorways on the concentration of traffic accidents in the Tarragona to El Vendrell area (moving north-eastwards) and in the Tarragona to Amposta area (heading south-westwards). It also shows the concentrations along the C14 and A27, respectively running northwards from Reus and Tarragona to the Valls area. These three areas maximum concentration, as expected, being in the metropolitan areas of Tarragona and Reus. Nevertheless, the concentration rates were lower than before lockdown. The red, orange and yellow surfaces vanished. The Valls area remains as the only secondary hotspot on the map in Figure 4 (bottom). Table 3 shows the distribution of traffic accidents taking into account whether they occurred on weekdays or at weekends/holidays. More than two thirds occurred at weekdays in 2018-2019. This matches the distribution of days between weekdays and weekends/holidays; as a result, the daily averages were almost identical (3.4-3.5). This ratio was different in 2020, when the average daily incidence of accidents on weekdays was higher (1.7-2.5). The reduction in the number of traffic accidents at weekends/holidays (-85%) was more intense than on weekdays in 2020. Nevertheless, the greatest difference was observed when This reduction in the number of accidents was consistent with the reduction in mobility during the latter period (Table 4) . Moreover, the reduction in the number of accidents was greater than the overall reduction in mobility. According to data from the Spanish Ministry of Transport, Mobility and Urban Agenda, the reduction in mobility in the province of Table 5 shows the distribution of traffic accidents taking into account whether they occurred on urban or interurban roads. Accidents on interurban roads accounted for more than 70% of the total. Accidents are more frequent on interurban roads than on those in cities and towns. The reduction in the number of traffic accidents over the whole study period, comparing 2020 with 2018-2019, was greater on urban than on interurban roads (-48% and -29%, respectively). The incidence of urban and interurban traffic accidents rose during the second period in 2018-2019; this was especially true of urban traffic accidents. Nevertheless, and as expected in a typical situation, the difference in their distributions was not statistically significant (χ2 = 0.86). In 2020, the reductions in the number of traffic accidents during the lockdown period were very similar on urban and interurban roads (75% and 73%, respectively). The reduction in mobility due to COVID-19 might have been expected to produce a greater decrease in the number of traffic accidents in urban areas, where speeds are lower, but this hypothesis was not supported by the data analysed. Despite the dramatic decrease in the number of traffic accidents on both urban (-83%) and interurban (-73%) roads, when the lockdown period was compared to the equivalent periods in 2018-2019, the differences in distribution were not statistically significant (χ2 = 1.22). The inhabitants of Tarragona and Reus account for 29% of the total population of Tarragona province. During the 12 weeks analysed for 2018-2019, three out of every 10 traffic accidents on urban roads occurred in one of these two cities. The total number of accidents declined during the same period in 2020, but its relative weight increased to 37%. The same pattern was found when we compared the periods before and during the lockdown in 2020: one in three before lockdown, but one in two during lockdown. Journal Pre-proof In 2020, the number of traffic accidents decreased on all three types of road networks when comparing the periods before and during lockdown. This reduction was especially evident on secondary roads (-89%) and motorways (-69%). As a result, despite the evident decrease in the number of road accidents on conventional basic roads (-59%), the relative weight of traffic accidents on these roads actually increased from 43.2% to 50%. Nevertheless, the difference in their distribution was not statistically significant (χ2 = 5.97 2 ); this was also the case when we compared the period before the lockdown with the equivalent periods in 2018-2019 (χ2 = 4.70). 2 It would be statistically significant if χ2 > 5.99. Our findings show that the lockdown decreed by the Spanish Government on March 14 2020, as a measure to drastically reduce the spread of COVID-19 disease, produced a significant reduction in traffic accidents in Tarragona province. While the number of traffic accidents may vary from year to year, or even season to season, the tremendous difference in the number occurring during the study period in 2020 and equivalent periods in 2018-2019, as also between the periods before and during lockdown, could mainly be attributed to the lockdown. The probability of having a traffic accident is higher when there are more vehicles on the roads. Moreover, our findings indicate that the degree of traffic accidents reduction has been higher than the reduction of mobility flows in the province. This would suggest than a reduction of transit in the roads should have a multiplicative effect in the reduction of accidents and injuries. The number of traffic accidents registered in early spring is greater than in late winter under normal circumstances. This is due to an increase in mobility in spring, mainly associated with travel for leisure and tourism (more hours of sunlight and nicer weather), which is particularly relevant at weekends. In addition, the Easter holidays coincided with the second period, which normally implies more vehicles on the roads and therefore an increase in the number of accidents. In fact, there were more traffic accidents during the pre-lockdown period in 2020 than in the equivalent periods corresponding to 2018-2019. An increase in traffic accidents was therefore to be expected in spring 2020. However, the lockdown changed this pattern. This change was consistent with phenomena reported by Shilling and Waetjen (2020) , who compared the incidence of traffic accidents before and during the lockdown in California, and by Brodeur et al. (2020) , whose study covered five US states. Safer-at-home policies reduced the number of traffic collisions and hence the number of people killed or seriously injured on the road. The number of traffic accidents involving people being injured or trapped fell more noticeably than less severe collisions. According to the Catalan Traffic Service (SCT, 2020), period and the corresponding periods in 2018-2019, the greatest reduction in serious accidents was observed on basic conventional roads when comparing the period during the lockdown and the equivalent periods in 2018-2019 but on secondary roads when comparing the periods before and during lockdown in 2020. Even so, the anomalous effects that measures to combat the COVID-19 crisis had on the incidence of traffic accidents did not cause any significant changes to their distribution patterns. The ongoing COVID-19 pandemic is having a major impact on health, but has also affected numerous economic and social phenomena on an almost unprecedented scale. It is currently affecting almost all facets of society, modifying our lifestyle and general behaviour. Mobility has been no exception in this respect, and even more so when modern society is characterized by hypermobility at multiple scales (Cohen and Gössling, 2015) . Mobility declined significantly in all countries when lockdowns were imposed, as in the case of Spain. Nevertheless, the restrictions placed on mobility gradually evolved in the weeks after the lockdown began, allowing the mobility of a larger numbers of people and activities in later weeks. Unfortunately, this also led to an increase in traffic accidents and in the resulting deaths and injuries. In the case of Tarragona province, our findings revealed an upward trend in traffic accidents in the last week of the study. Furthermore, the number of traffic accidents would then probably have continued to increase with respect to the equivalent period in previous years, due to more private vehicles being driven due to a possible reluctance to use public transportation (Aloi et al., 2020; De Vos, 2020; Gutiérrez et al., 2020; Musselwhite et al., 2020) , associated with maintaining social distance. There is a real risk that the clearly positive impacts of restricted mobility on traffic accidents could only remain in the short term. The same could apply to the benefits for human health associated with the reduction in atmospheric pollution, improved air quality, and reduced noise levels that have been linked to the COVID-19 crisis, especially in cities. In fact, Isalfan (2020) has argued that, in the case of China, the lockdown imposed by the government may J o u r n a l P r e -p r o o f Journal Pre-proof have saved more lives by reducing air pollution (all sources considered) than it has done by preventing the spread of infection. The unexpected benefits of the COVID-19 crisis will therefore probably only persist if the lockdown is maintained (which is neither expected nor desired) or if new public policies are designed and implemented with the objective of facilitating a gradual change in patterns of production, mobility, and consumption. COVID-19 offers both an opportunity and a challenge for public administrations (at the national, regional, and municipal levels): to apply policies designed to reduce mobility (King and Krizek, 2020). Our findings reveal that decrease of mobility implies a higher decrease of accidents and injuries. This happens in the whole studied period. Moreover, as higher is the reduction of mobility (weekends or holidays) higher is the relative differential with the decrease of accidents and injuries. Serafimova (2020) Transport which "delivers safe, secure and equitable mobility that embeds social, economic and environmental wellbeing at the heart of post-COVID transport policy, planning and operations and enables individuals to make considered transport choices". The same authors have outlined a series of debates and decisions that should involve local citizens in the search for the most suitable modes of transport. COVID-19 may serve as the catalyst that helps to shift policies on mobility (particularly in cities) towards more environmentally friendly and citizen-focused solutions. According to Nieuwenhuijsen and Khreis (2017) , cities should become partly private car-free, reduce motorized traffic, invest in cycling infrastructure and pedestrianization, restrict parking spaces, and increase the availability of public transport. Such initiatives would reduce mobility associated with private motor vehicles, but also the number of traffic accidents and J o u r n a l P r e -p r o o f Journal Pre-proof levels of urban pollution. This could be achieved in a planned and negotiated way, instead of being abruptly imposed, and would therefore contribute to meeting UN Sustainable Development Goals 3 (Good health and well-being), 11 (Sustainable cities and communities) and 13 (Climate action). The main limitations of our study derived from the data source used. As mentioned in the data and methods section, the information available to us made it possible to geolocate serious accidents and injuries and to determine the days on which they occurred. We did not, however, have information about the exact time of each accident, the speed at which it took place, the typologies of the vehicles involved, or the number of people involved, amongst other relevant factors. Similarly, we lacked access to new data after the lockdown. As a result, the evolution of cases after the progressive reestablishment of mobility has not been reported in this study. Taking these limitations into account, and also a series of new questions arising from our research, we feel that a number of interesting issues remain to be investigated in future research. The evolution of traffic accidents after the lockdown period should be studied. At the time of writing the current article, new outbreaks of disease were reappearing in different parts of Spain. As a consequence, several new, partial mobility, restrictions were applied in provinces neighbouring Tarragona. It would therefore be interesting to compile a continuous and dynamic report on: measures taken to restrict mobility; the evolution of mobility flows; and their influence on the increase/decrease in road traffic accidents. Results from this case study could provide useful insights and lessons for other parts of Spain. On the other hand, a growing number of studies are already highlighting the disruptive effects that the pandemic has had on travel behaviour, at multiple scales, around the world. As a consequence, it has been underlined that the pandemic could become a catalyst for medium to long-term changes in mobility and transportation at the local and global levels (Budd and Ison, 2020; De Vos, Effect of the COVID-19 lockdown on urban mobility Kernel density estimation and K-means clustering to profile road accident hotspots Good in the worst: COVID-19 restrictions and ease in global air pollution. Preprints, 040069 Insights into the impact of COVID-19 on household travel and activities in Australia -The early days under restrictions Identification of hazardous road locations of traffic accidents by means of kernel density estimation and cluster significance evaluation Real Decreto 463/2020, de 14 de marzo, por el que se declara el estado de alarma para la gestión de la situación de crisis sanitaria ocasionada por el COVID-19 On the effects of COVID-19 safer-at-home policies on social distancing, car crashes and pollution Responsible Transport: A post-COVID agenda for transport policy and practice Effects of traffic volumes on accidents: The case of Romania's national roads Road traffic noise in Montreal and environmental equity: what is the situation for the most vulnerable population groups Variations in volumes and characteristics of trauma patients admitted to a level one trauma centre during national level 4 lockdown for COVID-19 in New Zealand A darker side of hypermobility How COVID-19 and the Dutch 'intelligent lockdown' change activities, work and travel behaviour: Evidence from longitudinal data in the Netherlands The effect of COVID-19 and subsequent social distancing on travel behavior Evolución de tráfico por el efecto de COVID-19, Dirección General de Tráfico, Ministerio del Interior The impact of government measures and human mobility trend on COVID-19 related deaths in the UK Development and application of traffic accident density estimation models using kernel density estimation Transportation noise exposure and cardiovascular mortality: a nationwide cohort study form Switzerland Vehicle insurance and the risk of road traffic accidents The dramatic impact of Coronavirus outbreak on air quality: Has it saved as much as it has killed so far? Is a liveable city a healthy city? Health impacts of urban and transport planning in Vienna Urban transport and COVID-19: challenges and prospects in low-and middle-income countries Traffic fatalities and economic growth The effect of human mobility and control measures on the COVID-19 epidemic in China COVID-19 presents opportunities and threats to transport and health The association between international and domestic air traffic and the coronavirus (COVID-19) outbreak The impact of COVID-19 on transport volume and freight capacity dynamics: An empirical analysis in German food retail logistics Relationship between crash rate and hourly traffic flow on interurban motorways Urban and transport planning related exposures and mortality a health impact assessment for cities Editorial JTH 16 -The Coronavirus Disease COVID-19 and implications for transport and health The positive effects of COVID-19 Car free cities: pathway to healthy urban living Integrating human health into urban and transport planning Impact of the COVID-19 pandemic on an emergency traumatology service: experience at a tertiary trauma centre in Spain COVID-19 lockdowns and decline in traffic related deaths and injuries Current understanding of the effects of congestion on traffic accidents Transport geography, climate change and space: opportunity for new thinking Balanç de sinistralitat fins abril de 2020, Servei Català de Trànsit, Departament d'Interior, Generalitat de Catalunya Covid-19: an opportunity to redesign mobility towars greater sustainability and resilience? Robert Schuman Centre for Advanced Studies Congestion, air-pollution, and road fatalities in urban areas Special Report: Impact of COVID19 on California Traffic Accidents Adolescent driving behavior before and during restrictions related to COVID-19 Land use, transport, and population health: estimating the health benefits of compact cities Analysis of safety factors for urban expressways considering the effect of congestion in The link between bike sharing and subway use during the COVID-19 pandemic: The case-study of New York's City Bike The effect of traffic and road characteristics on road safety: A review and future research direction Spatio-temporal analysis of the impact of congestion on traffic safety on major roads in the UK Global status report on road safety 2018. World Health Organization Nowcasting and forecasting the potential domestic and international spread of the 2019-nCoV outbreak originating in Wuhan, China: a modelling study Detecting traffic accident clusters with network kernel density estimation and local spatial statistics: an integrated approach Relationship between volume-to-capacity ratios and accident rates We would like to thank the Directorate-General of Fire Prevention, Extinction and Rescue (DGPEIS) of the Generalitat de Catalunya for providing data on traffic accidents. This research did not receive any specific grant support from funding agencies operating in the public, commercial, or not-for-profit sectors.