Costs and benefits to Sweden of Swedish road safety research

A comparative analysis of accident modification functions for traffic law enforcement

Traffic law enforcement is a road safety measure whose effects on accidents or injuries is best described by means of a function rather than a point estimate. An informative function should comprise both increases and decreases in enforcement. Currently available accident modification functions cannot serve this need. A fruitful approach to developing accident modification functions covering both increases and decreases in enforcement is differences-in-differences estimates based on multivariate accident prediction models. The paper explains how to develop such estimates and illustrates them. The interpretation of the results of empirical studies can be informed by a game-theoretic model of the effects of enforcement, previously published in Accident Analysis and Prevention (Bjørnskau and Elvik 1992, 507-520).

A comprehensive conceptual framework for road safety strategies

Road safety strategies (generally called Strategic Highway Safety Plans in the USA) provide essential guidance for actions to improve road safety, but often lack a conceptual framework that is comprehensive, systems theory based, and underpinned by evidence from research and practice. This paper aims to incorporate all components, policy tools by which they are changed, and the general interactions between them. A framework of nine mutually interacting components that contribute to crashes and ten generic policy tools which can be applied to reduce the outcomes of these crashes was developed and used to assess 58 road safety strategies from 22 countries across 15 years. The work identifies the policy tools that are most and least widely applied to components, highlighting the potential for improvements to any individual road safety strategy, and the potential strengths and weaknesses of road safety strategies in general. The framework also provides guidance for the development of new road safety strategies, identifying potential consequences of policy tool based measures with regard to exposure and risk, useful for both mobility and safety objectives.

What is the effect of reduced street lighting on crime and road traffic injuries at night? A mixed-methods study

Background

Some local authorities have reduced street lighting at night to save energy, but little is known about impacts on public health or about public concerns about impacts on well-being.

Aim

To evaluate the effect of reduced street lighting on crime and road traffic injuries.

Design

A mixed-methods study comprising a rapid appraisal, a controlled interrupted time series analysis and a cost–benefit analysis (CBA).

Setting

England and Wales.

Target population

Residents and workers in eight case study areas; road traffic casualties and victims of crime.

Interventions evaluated

Switch-off (i.e. lights permanently turned off), part-night lighting (e.g. lights switched off between 12 a.m. and 6 a.m.), dimming lights and white lights/light-emitting diodes (LEDs).

Outcomes

Public views about implications on well-being; road traffic injury data (STATS19:http://data.gov.uk/dataset/road-accidents-safety-data) obtained for the period 2000–13; crime data (Police.uk:data.police.uk) obtained for the period December 2010–December 2013. Detailed crime data were obtained from one police force for a methodological study of the spatial level at which Police.uk data are valid for analysis.

Statistical methods

Road traffic collisions were analysed at street segment level. Regression models were used to estimate changes in daytime and night-time collision rates associated with lighting interventions. The ratio of night-time and daytime changes was considered the best estimate of change in night-time collisions following each lighting intervention. Police.uk crime data were found to be reliable when analysed at middle super output area (MSOA) level. For crime, the analysis used the proportion of total km of road in each MSOA with each lighting intervention. Regression models controlled for yearly and monthly trends and were fitted in each geographical region and police force. Effect estimates were pooled in random-effects meta-analyses.

Results

Public concerns centred on personal security, road safety, crime, fear of crime, sleep quality and being able to see the night sky. Street lighting reductions went largely unnoticed or had only marginal impacts on well-being, but for a minority of people switch-off and part-night lighting elicited concerns about fear of the dark, modernity and local governance. Street lighting data were obtained from 62 local authorities. There was no evidence that reduced street lighting was associated with road traffic collisions at night. There was significant heterogeneity in the estimated effects on crime at police force level. Overall, there was no evidence that reduced street lighting was associated with crime. There was weak evidence for a reduction in crime associated with dimming [rate ratio (RR) 0.84, 95% confidence interval (CI) 0.70 to 1.02] and white light (RR 0.89, 95% CI 0.77 to 1.03). The CBA suggests that part-night lighting may represent a net benefit to local authorities.

Limitations

The study did not account for the impacts of other safety/crime prevention initiatives (e.g. improved road markings; closed-circuit television), and so associations may be partly attributable to these initiatives. The CBA was unable to include potentially important impacts such as fear of crime and reduced mobility.

Conclusion

This study found little evidence of harmful effects of switch-off, part-night lighting, dimming or changes to white light/LEDs on levels of road traffic collisions or crime in England and Wales. However, the public were also concerned about other health outcomes. Research is needed to understand how lighting affects opportunities for crime prevention and how these vary by context. Research is needed also on other public health impacts of light at night.

Funding

The National Institute for Health Research Public Health Research programme.

Cost benefit analysis of 20 mph zones in London

Evidence suggests that 20 mph zones are an effective intervention to reduce casualties from road traffic crashes in urban areas. This analysis compares the costs of construction of the 20 mph zone intervention in high and low casualty areas in London to the value of casualties avoided over 5 and 10 year time horizons. Probabilistic sensitivity analyses were conducted to quantify uncertainty in the results associated with model parameters. Results indicate a net present value (NPV) of £18 947 (90% credible limits -£75 252 to £82 021 2005 prices) after 5 years and £67 306 (£-29 157 to £137 890) after 10 years when 20 mph zones are implemented in areas with one or more casualty per kilometre of road. Simulations from our model suggest that the 'threshold of casualties' where NPVs become positive using a 10 year time horizon is 0.7 casualties per kilometre.

Seatbelt compliance and mortality in the Gulf Cooperation Council countries in comparison with other high-income countries

BACKGROUND AND OBJECTIVES

Mortality from road traffic collisions (RTC) is a major problem in the Gulf Cooperation Council (GCC) countries. Low compliance with seatbelt usage can be a contributing factor for increased mortality. The present study aimed to ascertain the presence of a relationship between seatbelt non-compliance of vehicle occupants and mortality rates in the GCC countries versus other high-income countries.

DESIGN AND SETTING

Observational and descriptive study using information published by the World Health Organization.

METHODS

Data for all GCC countries (n=6) and other high-income countries (n=37) were retrieved and compared with regard to population, gross national income, number of vehicles, seatbelt non-compliance and road traffic death rates. Univariate and multivariate analysis were used to define factors affecting the mortality rates.

RESULTS

The median road traffic death rates, occupant death rates, and the percentage of seatbelt non-compliance were significantly higher in the GCC countries (P<.0001, P=.02, P<.001, respectively). There was a strong correlation between occupant death rates and seatbelt non-compliance (R=.52, P=.008). Seatbelt non-compliance percentage was the only significant factor predicting mortality in the multiple linear regression model (P=.015).

CONCLUSIONS

Seatbelt non-compliance percentages in the GCC countries are significantly higher than in other high-income countries. This is a contributing factor in the increased road traffic collision mortality rate in these countries. Enforcement of seatbelt usage by law should be mandatory so as to reduce the toll of death of RTC in the GCC countries.

Seatbelts and road traffic collision injuries

Modification of seatbelts and their legislation played an important role in reducing morbidity and mortality of occupants in road traffic collisions. We aimed to review seatbelt development, its mechanism of action and its effects. Seatbelts reduce injury by preventing the occupant from hitting the interior parts of the vehicle or being ejected from the car. We have made a linear regression correlation between the overall seatbelt compliance and road traffic death rates in 46 high income countries to study the relationship between seatbelt use and mortality. There was a very highly significant negative correlation between the seatbelt compliance and road traffic death rates (R = - 0.77, F = 65.5, p < 0.00001). Seatbelt-related injuries include spinal, abdominal or pelvic injuries. The presence of a seatbelt sign must raise the suspicion of an intra-abdominal injury. These injuries can be reduced if seatbelts were applied correctly. Although seatbelts were recognized as an important safety measure, it still remains underused in many countries. Enforcement of seatbelt usage by law is mandatory so as to reduce the toll of death of road traffic collisions.

Sources of uncertainty in estimated benefits of road safety programmes

National road safety programmes have been developed in many motorised countries. Some of these programmes contain estimates of the safety benefits that were expected to be realised if the programmes were fully implemented. When these estimates are compared to actual outcomes, it is not uncommon to find large differences. This paper argues that differences between the predicted and actual results of road safety programmes could be the result of a large, but generally unrecognised, uncertainty inherent in estimates of the effects of such programmes. Ten sources of uncertainty are identified and briefly described. The possibility of describing these sources of uncertainty numerically, and of estimating their joint contribution, is discussed. It is concluded that at the current state of knowledge, it is not possible to meaningfully estimate the total uncertainty inherent in road safety programmes. The prospects of reducing uncertainty by means of research are discussed.