Speed related variables for crash injury risk analysis: what has been used?

Travelling Speed and the Risk of Crash Involvement: Volume 1: Findings

1997

The relationship between free travelling speed and the risk of involvement in a casualty crash in a 60 km/h speed limit zone was quantified using a case control study design. The 151 case vehicles were passenger cars involved in crashes in the Adelaide metropolitan area which were investigated at the scene by the NHMRC Road Accident Research Unit at Adelaide University and reconstructed using the latest computer aided crash reconstruction techniques. The 604 control vehicles were passenger cars matched to the cases by location, direction of travel, time of day, and day of week and their speeds were measured with a laser speed gun. It was found that the risk of involvement in a casualty crash doubled with each 5 km/h increase in free travelling speed above 60 km/h. Hypothetical speed reductions applied to the case vehicles indicated large potential safety benefits from even small reductions in travelling speed, particularly on arterial roads. (a)

Driving speed and the risk of road crashes: A review

Accident Analysis & Prevention, 2006

Driving speed is an important factor in road safety. Speed not only affects the severity of a crash, but is also related to the risk of being involved in a crash. This paper discusses the most important empirical studies into speed and crash rate with an emphasis on the more recent studies. The majority of these studies looked at absolute speed, either at individual vehicle level or at road section level. Respectively, they found evidence for an exponential function and a power function between speed and crash rate. Both types of studies found evidence that crash rate increases faster with an increase in speed on minor roads than on major roads. At a more detailed level, lane width, junction density, and traffic flow were found to interact with the speed-crash rate relation. Other studies looked at speed dispersion and found evidence that this is also an important factor in determining crash rate. Larger differences in speed between vehicles are related to a higher crash rate. Without exception, a vehicle that moved (much) faster than other traffic around it, had a higher crash rate. With regard to the rate of a (much) slower moving vehicle, the evidence is inconclusive.

Analysis of effect of speed-limit increases on accident causation and injury severity

2008

The influence of speed limits on roadway safety has been a subject of continuous debate in the State of Indiana and nationwide. In Indiana, highway-related accidents result in about 900 fatalities and forty thousand injuries annually and place an incredible social and economic burden on the state. Still, speed limits posted on highways and other roads are routinely exceeded as individual drivers try to balance safety, mobility (speed), and the risks and penalties associated with law enforcement efforts. The speed-limit/safety issue has been a matter of considerable concern in Indiana since the state raised its speed limits on rural interstates and selected multilane highways on July 1, 2005. In this paper, the influence of the posted speed limit on the severity of vehicle accidents is studied using Indiana accident data from 2004 (the year before speed limits were raised) and 2006 (the year after speed limits were raised on rural interstates and some multi-lane non-interstate routes). Statistical models of the injury severity of different types of accidents on various roadway classes were estimated. The results of the model estimations showed that, for the speed limit ranges currently used, speed limits did not have a statistically significant effect on the severity of accidents on interstate highways. However, for some non-interstate highways, higher speed limits were found to be associated with higher accident severitiessuggesting that future speed limit changes, on non-interstate highways in particular, need to be carefully assessed on a case-by-case basis.

Analysis of the Effect of Speed Limit Increases on Accident-Injury Severities

Proposed vehicle impact speed - severe injury probability relationships for selected crash types

2015

Speed is recognised as a key contributor to crash likelihood and severity, and to road safety performance in general. Its fundamental role has been recognised by making Safe Speeds one of the four pillars of the Safe System. In this context, impact speeds above which humans are likely to sustain fatal injuries have been accepted as a reference in many Safe System infrastructure policy and planning discussions. To date, there have been no proposed relationships for impact speeds above which humans are likely to sustain fatal or serious (severe) injury, a more relevant Safe System measure. A research project on Safe System intersection design required a critical review of published literature on the relationship between impact speed and probability of injury. This has led to a number of questions being raised about the origins, accuracy and appropriateness of the currently accepted impact speed–fatality probability relationships (Wramborg 2005) in many policy documents. The literature...

A Comprehensive Review on Risk Factors Affecting the Crash Severity

paper, 2019

As a matter of growing machinery life, traffic crashes are considered an inevitable source of injuries and costs around the world. Regarding to increasing traffic accident outcomes, controlling the current status is necessary. In this way, identifying risk factors affecting the crash severity is an essential step toward initiating a convincing solution. The core objective of this study was to categorize the risk factors affecting the severity of crashes. Data needed for this study were gathered through searching Web of Science, Google Scholar, and Science Direct databases using the keywords included fatal and crash, injuries and crash, fatal and traffic accident, and injuries and traffic accident. Based on 83 selected studies for review, factors affecting the crash severity divided into five factors and forty-seven sub-factors. The most prevalent sub-factors were age, sex, safety belts, alcohol and drug use, speed, weather conditions, lighting conditions, time of the day and week, v...

Exploration of Vehicle Impact Speed – Injury Severity Relationships for Application in Safer Road Design

Transportation Research Procedia, 2016

The Safe System vision (known as Vision Zero, or Sustainable Safety in Europe) aspires to minimise death and serious injury as an outcome of road travel for all road users. The road engineering contribution to this vision focusses on impact elimination, or where this is not possible, on limiting kinetic energy passed to a road user in case of an impact. Impact kinetic energy is typically limited through vehicle speed management (e.g. speed limits, enforcement or geometric road design), as vehicle mass is difficult to effectively control by public road agencies. This paper reviews available international research on relationships between impact velocity change (delta-v), impact speeds and the probability of fatal and serious injury (MAIS3+) across a range of common crash scenarios. Based on the best identified relationships, and with assumption of equal mass and vehicle speeds, right-angle and head-on impact speeds of approximately 30 km/h are likely to produce MASI3+ injury probability of approximately 10%, considered a critical threshold in Safe System discussions. For pedestrians, the threshold is likely to be even lower, approximately 20 km/h. In rear-end crashes, the critical impact speed was found to be approximately 55 km/h. Some practical applications of these findings are discussed. The paper discusses the assumptions and limitations behind the available evidence, and outlines the proposed research to strengthen it.

Speed limits and accident rates on highways around the world, is there a correlation?

IOP Conference Series: Earth and Environmental Science, Proceedings of the 2nd International Conference on Environmental Design (ICED 2021), 2021

The objective of this study stands for the investigation and evaluation of accidents that take place on highways, in comparison with speed limits. The main body of this research is based on the collection of highways speed limits from different countries around the globe regarding to years, 2010, 2017 and 2018. Secondly, accident rates are collected from highway authorities, as well as from international literature. Subsequently, a statistical analysis of the collected data is conducted and finally leads to an equation that links and correlates the speed limit values and the number of accidents. The results of this statistical analysis show that speed limit plays a certain and distinctive role in the accident rate value. However, one of the interesting findings, stands for the non-continuously increasing number of accidents in the speed limit range, from the lowest to the highest value, meaning that there is an inflection point in the graph of the correlation equation. To be noted, that in terms of this study, the aforementioned correlation is independent of other factors that could affect the accident rate, such as vehicles condition, technology, road network length and condition.

Understanding the role of Speeding and Speed in Serious Crash Trauma: A Case Study of New Zealand

Journal of Road Safety, 2022

Multiple sources of evidence address the contribution of speed and speeding in crashes: police crash reports, in-depth crash investigations, studies of speed and serious crash risk, assessments of survival and injury rates for various impact speeds, and evaluations of the safety outcomes of speed management interventions. These sources of evidence all indicate that speed is a major factor in crash trauma, but appear to differ in estimates of the extent of the role of speed. This paper employs New Zealand as a country case study, undertaking a targeted assessment of data from the different sources to better determine the roles of speed and speeding in serious crashes. We find that apparent mismatches of estimates of the role of speed from different sources largely arise for two reasons. First, the studies vary in methodology and thus validity, and second the data from the different sources provide answers to fundamentally different questions, which are then incorrectly subsumed into ...

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