Traffic-Calming Measures and Road Traffic Collisions and Injuries: A Spatiotemporal Analysis

Traffic-calming measures (TCMs) are physical modifications of the road network aimed at making the roads safer. Although researchers have reported reductions in numbers of road crashes and injuries tied to the presence of TCMs, such studies have been criticized for their pre-/post- designs. In this study, we aimed to complement our knowledge of TCMs' effectiveness by assessing their impact using a longitudinal design. The implementation of 8 TCMs, including curb extensions and speed humps, was evaluated at the intersection and census tract levels in Montreal, Quebec, Canada, from 2012 to 2019. The primary outcome was fatal or serious collisions among all road users. Inference was performed using a Bayesian implementation of conditional Poisson regression in which random effects were used to account for the spatiotemporal variation in collisions. TCMs were generally implemented on local roads, although most collisions occurred on arterial roads. Overall, there was weak evidence that TCMs were associated with study outcomes. However, subgroup analyses of intersections on local roads suggested a reduction in collision rates due to TCMs (median incidence rate ratio, 0.31; 95% credible interval: 0.12, 0.86). To improve road safety, effective counterparts of TCMs on arterial roads must be identified and implemented.

Spherical Cap Studs: A novel speed bump alternative to reduce discomfort with effective speed reduction

OBJECTIVE

The aim of this study is to assess the potential of Spherical Cap Studs (SCS) as a substitute for conventional speed bumps, with a focus on limiting two wheeler speed while minimizing discomfort to riders by comparing the speed reduction capabilities and discomfort levels associated with SCS and speed bumps.

METHODS

The study uses experimental approach to compare the speed limiting ability and discomfort caused to rider by the proposed SCS and a standard speed bump. Speed profiles were developed for two wheelers passing over both SCS and speed bump. The parameter employed to compare speed profiles is the Mean Absolute Percentage Difference (MAPD), offering valuable insights into how effectively the two traffic calming measures reduce two wheeler speeds. To compare discomfort, the study calculates the 'Vibration Dose Value' (VDV) experienced by riders when traversing both speed bump and SCS. Additionally, 'Static Compressive Stress' (Se) applied to the spinal cord is also calculated in both scenarios.

RESULTS

The analysis of speed profiles reveals an MAPD value of 13.70% indicating that SCS exhibits speed reduction capabilities comparable to traditional speed bump. In terms of discomfort, the VDV for two wheelers passing over a speed bump is measured at 5.92 m/s1.75, whereas the VDV for SCS is found to be 5.16 m/s1.75. Similarly, the Static Compressive Stress (Se) experienced at a speed bump is 0.60 MPa, in contrast to the 0.33 MPa recorded for SCS. This data underscores a noteworthy 12.8% reduction in VDV and a substantial 45.57% reduction in Se.

CONCLUSION

The study's findings support the potential adoption of SCS as an effective alternative to conventional speed bumps for controlling two wheeler speeds. SCS demonstrate a speed reduction capability similar to that of traditional speed bumps while significantly alleviating discomfort for riders. SCS is expected to be a promising solution for traffic calming purposes in various settings, such as markets, residential areas, institutional campuses, and parking lots.

A new model to estimate pedestrian deaths from speed-related interventions

OBJECTIVE

The S-shaped function of probability of pedestrian fatality with respect to impact speed of vehicle is well known in road safety literature. However, the implication of this evidence for changes in speed for a population of drivers has not been explored.

METHOD

An integrated model has been developed to estimate pedestrian fatalities resulting from changes in speed of traffic. The model uses combined relative risks of injury crash rate of drivers and probability of pedestrian fatality resulting from an injury crash. Two approaches have been used-an individual approach using probability distribution of speed, and an aggregate approach, using only mean speed. The application of the model has been demonstrated using four case studies with speed of traffic before and after an intervention.

RESULTS

It is found that even small reductions in mean speed translate to large reductions in pedestrian fatalities. The risk contributed by speeding vehicles is highly disproportionate to their share in vehicle population. In a case study from Delhi (India), in which at-grade junction was replaced with a grade-separated junction, 74% of risk of pedestrian fatalities is contributed by less than 5% speeding vehicles (>50km/h). Changes in mean speed is a poor indicator of changes in injury risk if the standard deviation of the distribution also changes significantly. A surprising finding was that large variation in the S-shape of pedestrian fatality risk function has relatively small effects on overall results.

CONCLUSIONS

A new model has been developed to estimate changes in pedestrian fatalities resulting from changes in traffic speed. The application of the model using four speed-related interventions emphasize that deterrence of a small proportion of drivers using speed enforcement can have large implications for pedestrian safety.

Preventing motor vehicle crash injuries and deaths: science vs. folklore lessons from history

Not long after the beginnings of motorization in the early 1900s, deaths and injuries from motor vehicle crashes became a problem in a number of high-income-countries (HIC)s, especially the United States. With the biggest problem the US led early efforts to address this issue, and for six decades these efforts were based on folklore (ie a body of widely held but false or unsubstantiated beliefs). They were not evaluated, but clearly were unsuccessful as crash deaths and injuries continued to rise. It was not until the 1970s that a broader range of countermeasures began to be adopted and was scientifically evaluated, and as a result, crash deaths and injuries declined. This history has important lessons today for many low-and-middle-income countries that have growing numbers of motor vehicle crash deaths and injuries, many of which are pedestrians and motorcyclists. This is because there continue to be advocates for many of the failed approaches (especially educational) that dominated the early efforts in HICs.

Speed in a high-speed society

Speed control is the most important aspect of promoting road safety world-wide. The question is how are speeds developing? The European Transport Safety Council concludes: There is little progress on reducing speeds in Europe. Similar conclusions can be drawn from the US and Australia. Attitude surveys show that people's answers are not very consistent and represent statements without any strong bearing on norms or behaviour. Many factors are 'pro-speed': higher performance vehicles, more comfort, media coverage, etc. Enforcement, particularly with cameras and with section control is efficient, but the scale of adoption is too small. Traffic calming is efficient in cities, but the most obvious measure is one that makes it impossible to drive faster than the speed limit. During the last 30 years, a few trials have taken place which are promising; speeds at or below the speed limit, improved behaviour, and attitudes. The predicted effect is a reduction of up to 50% of fatalities in a regulation-driven scenario and a benefit to cost ratio of 3.5 to 4.8. It is time for authorities to see to it that lower speeds with the help of efficient vehicle-based solutions becomes part of the agenda.

The Effect of Brick and Granite Block Paving Materials on Traffic Speed

Slowing traffic speed in urban areas has been shown to reduce pedestrian injuries and fatalities due to automobile accidents. This research aims to measure how brick and granite block paving materials, which were widely used historically prior to the use of asphalt paving in many cities, may influence free flow traffic speed. Traffic speeds for 690 vehicles traversing street blocks paved with asphalt, granite block, and brick materials were measured using a radar gun on a sample of 18 matched pair (asphalt and historic paving material) street blocks in Philadelphia, Pennsylvania. Fixed effects linear regression was used to estimate the effect of paving material on vehicle speed after controlling for the street class (e.g., arterial versus local road) and the matched pair. Results indicate that brick reduced speeds by approximately 3 mph (~5 km/h) and granite block reduced speeds by approximately 7 mph (~11 km/h), as compared to asphalt paved city streets, which we attribute to drivers intentionally slowing due to road roughness. This research suggests that brick and granite block paving materials may be an effective traffic calming strategy, having implications for reducing negative health outcomes associated with pedestrian–automobile collisions.

School Area Road Safety Assessment and Improvements (SARSAI) programme reduces road traffic injuries among children in Tanzania

PURPOSE

To determine the impact of a paediatric road traffic injury (RTI) prevention programme in urban Sub-Saharan Africa.

SETTING

Dares Salaam, Republic of Tanzania.

METHODS

Household surveys were conducted in catchment areas around 18 primary schools in Dar es Salaam, Republic of Tanzania; the catchment areas were divided into control and intervention groups. Collected data included basic demographic information on all school-aged household members and whether or not they had been involved in an RTI in the previous 12 months, and, if so, what the characteristics of that RTI were. Based on these findings, a separate road safety engineering site analysis and consultation with the communities and other stakeholders, an injury-prevention programme was developed and implemented, consisting of infrastructure enhancements and a site-specific educational programme. The programme was initially implemented at the intervention schools. After 1 year, data were collected in the same manner. The control group received the same intervention after follow-up data were collected.

RESULTS

Data were collected on 12 957 school-aged children in the baseline period and 13 555 school-aged children in the post-intervention period, in both the control and intervention communities. There was a statistically significant reduction in RTIs in the intervention group and a non-significant increase in RTI in the control group. The greatest reduction was in motorcycle-pedestrian RTI, private vehicle-pedestrian RTI and morning RTI.

CONCLUSION

The programme demonstrated a significant reduction in paediatric RTI after its implementation, in very specific ways. This study demonstrates that for a reasonable investment, scientifically driven injury-prevention programmes are feasible in resource-limited settings with high paediatric RTI rates.

Investigation of the impact of low cost traffic engineering measures on road safety in urban areas

This paper investigates the impact of low cost traffic engineering measures (LCTEMs) on the improvement of road safety in urban areas. A number of such measures were considered, such as speed humps, woonerfs, raised intersections and other traffic calming measures, which have been implemented on one-way, one-lane roads in the Municipality of Neo Psychiko in the Greater Athens Area. Data were analysed using the before-and-after safety analysis methodology with large control group. The selected control group comprised of two Municipalities in the Athens Greater Area, which present similar road network and land use characteristics with the area considered. The application of the methodology showed that the total number of crashes presented a statistically significant reduction, which can be possibly attributed to the introduction of LCTEMs. This reduction concerns passenger cars and single-vehicle crashes and is possibly due to the behavioural improvement of drivers of 25 years old or more. The results of this research are very useful for the identification of the appropriate low cost traffic engineering countermeasures for road safety problems in urban areas.