Chapter 11

• Driving behavior


  Speed, acceleration and braking behavior, reaction time, speed variance
• Sources of Risks in Traffic

  • Characteristics of transport flows
  • Driving behavior
  • Technology
• Risk-Increasing Factors in Traffic

  • Lack of Driving Experience
  • Psycho-active Substances (Alcohol and Drugs)
  • Fatigue
  • Distraction
• Challenges in Identifying Crash Causes

  • Police registration forms not designed to identify underlying causes of crashes
  • Crashes typically result from a combination of factors, making it difficult to pinpoint a single cause
• Psycho-active Substances (Alcohol and Drugs)

  1. Alcohol consumption significantly increases crash risk

  2. Road users under the influence of alcohol face higher crash risks

  3. Enforcement of zero-tolerance laws for alcohol and drugs has reduced drunk driving
• Speed as a Risk Factor

  • Speed is closely associated with crash risk and severity
  • Higher speeds exponentially increase crash risk and severity
  • Speed variance among road users also contributes to increased crash risk
• Distraction


  1. Distraction, particularly from activities like talking or texting on mobile phones, is a common cause of crashes

  2. Tasks requiring drivers to divert their eyes away from the road significantly increase crash risks
• Technology in traffic

  Plays a crucial role in enhancing safety, but certain technologies like mobile devices can pose risks
• Lack of Driving Experience

  1. Novice drivers face higher crash risks due to lack of experience

  2. Lack of experience contributes to about 60% of crash risk for novice drivers

  3. Male novice drivers face substantially higher crash risks compared to more experienced drivers and female novice drivers

  4. Crash risk for novice drivers decreases rapidly within the first year after passing a driving test
• Transport flow characteristics

  Traffic volume, modal split, composition of traffic, division over time, distribution over space
• Fundamental Risk Factors in Traffic

  • Traffic participation inherently involves risks due to several fundamental factors
  • Factors include vulnerability of road users' bodies, speed levels, presence of objects with significant mass and stiffness
  • Factors affecting driving behavior like alcohol use, fatigue, and distraction increase crash risk
• Mass Differences and Vulnerability in Traffic

  • Mass differences impact severity of injuries
  • Vulnerability of pedestrians and cyclists is a fundamental risk factor
  • Vehicle design improvements enhance safety but vulnerable road users still face risks
• Fatigue


  1. Fatigue impairs driving ability by reducing reaction time, course-keeping ability, compliance with traffic rules

  2. People suffering from sleep disorders or acute lack of sleep have higher crash risk
• Research on Violations and Crashes

  • Canadian study observed a decrease in fatal crash involvement after drivers were fined for violations related to fatal crashes
  • Strong relationship between violations and crash involvement, challenging to prove causality
  • Both errors and violations play a role in causing crashes, but exact share cannot be determined based on current knowledge
• Critique of Current Crash Causation Analysis Methods


  • Recent studies question the adequacy of current methods for analyzing crash causation, suggesting a need to link causes with countermeasures
  • There's a call to contextualize human errors, failures, and violations within the environment in which they occur, aiming to change behavior in a safer direction by adapting the environment
• Challenges in Identifying Crash Causes

  • Police registration forms are not designed to identify the underlying causes of crashes but rather to determine the guilty party
  • Crashes typically result from a combination of factors, making it difficult to pinpoint a single cause
  • Unintentional errors are likely more prevalent as crash causes, as intentional offending rarely leads directly to a crash. However, violations can increase the risk of errors and their severity
• Measuring Safety and Danger

  • Road safety is typically measured by the number of road crashes, casualties, and their negative consequences. Subjective perceptions of road safety, such as fears of being involved in a crash, are also sometimes considered
  • A widely accepted definition of a road traffic crash involves a collision or incident on a public road resulting in damage to objects and/or injury to people involving at least one moving vehicle
  • Road deaths are defined internationally as someone who dies immediately or within 30 days as a result of a road crash, excluding suicides
• Road Types and Risk Factors

  • Serious crashes on rural roads are often single-vehicle crashes caused by inappropriate speeds, combined with factors like alcohol consumption, distraction, and fatigue. Roadside design also contributes to the severity of outcomes
  • Urban roads see a high number of fatalities, primarily due to transverse conflicts (side impacts) where mass differentials and vulnerability of road users play significant roles
  • Motorways are the safest roads due to high-quality design and restrictions on slow-moving traffic
• Challenges in Data Collection

  • Crash registration is typically carried out by the police, but crash statistics are often incomplete due to underreporting. Crashes involving non-motorized transport and alcohol-related crashes are particularly prone to underreporting
  • Data collections also suffer from biases, with less severe injuries being more underreported
• Role of Driver Behavior in Crashes

  1. Driver inattention and errors are prevalent factors leading to crashes, often occurring just prior to the onset of conflict

  2. Observational systems installed in vehicles have provided insights into everyday driving behavior, revealing instances of driver inattention and errors that may not be captured in police reports
• Risks for transport modes, age groups, and road types cannot be determined based on current knowledge
• Transport Modes and Risk Factors

  • Motorized two-wheelers, such as motorcycles and mopeds, have the highest fatality and injury risk in road traffic due to their combination of high speed, low mass, and poor crash protection
  • Young people are at a higher risk in traffic due to age-specific characteristics, lack of driving experience, and their preference for two-wheelers
  • Elderly road users are also at a higher risk due to physical frailty
• Estimating Serious Injuries

  1. Serious injuries are often defined using the Maximum Abbreviated Injury Scale (MAIS), with MAIS 3+ considered serious. The European Union aims to reduce both road fatalities and serious injuries by using MAIS3+ as a criterion

  2. Methods for estimating serious injuries include corrections on police data, hospital data, and linked police and hospital data
• Estimating Road Crash Costs

  1. Estimating road crash costs is important for policy-making and can be compared with other impacts of traffic and transport as well as other public health issues

  2. Common cost categories include medical costs, production loss, human costs, property damage, and settlement costs

  3. Human costs involve estimating the value of a statistical life (VOSL) and the value of a statistical life
• Crash Risk Management

  1. Designing roads for high-speed conditions, such as motorways, requires both physical (e.g., separation of driving directions, grade-separated intersections) and psychological (e.g., predictable design) considerations to manage high speeds safely

  2. In areas where vulnerable road users and motorized traffic share space, low-risk conditions can only be achieved with low traveling speeds
• Each year, over 1.35 million road users are killed in road crashes worldwide, with 20 to 50 million suffering non-fatal injuries
• The socioeconomic costs of road crashes range from 0.5% to 6.0% of GDP in high-income countries and from 1.1% to 2.9% in low- and middle-income countries
• The Netherlands experienced a 50% reduction in the mortality rate from 1995 to 2007, attributed to various factors such as infrastructural adaptations, vehicle safety improvements, and enhanced legislation and enforcement
• Human costs


  Estimating the value of a statistical life (VOSL) and the value of a statistical serious injury (VSSI) reflecting people's willingness to pay for lower risks
• Challenges persist, such as speeding, which remains a concern despite lowered speed limits
• The reduction in road deaths is not solely due to decreased exposure (distance traveled), but also a result of interventions that reduce the fatality rate
• The Swedish perspective introduced the idea of considering exposure as a variable in understanding road safety, emphasizing the need to address the frequency of crashes relative to exposure
• In highly motorized countries, there are two types of road safety problems: generic and specific
• Initially, crashes were attributed to individual fault, leading to legal and insurance implications. Subsequently, the understanding shifted towards recognizing multiple contributing factors to crashes
• Specific problems relate to identifiable risk factors such as hazardous locations, high-risk road user groups, or defective vehicles
• There's growing recognition of the importance of safety culture and behavioral change in road safety
• Since 1970, many high-income countries have made significant progress in reducing road fatalities. However, progress has slowed in the last decade, except for 2020 due to the COVID-19 pandemic
• Despite increased mobility, the Netherlands has seen a significant decline in traffic fatalities. For instance, between 2010 and 2020, there were just over 600 traffic deaths annually, compared to 3,264 deaths in 1972
• Since the 2000s, two main approaches have emerged: Evidence-Based Policies and Safe System Approach
• Throughout the 20th century, road safety paradigms evolved from viewing crashes as chance occurrences to recognizing multi-causal factors