Traffic Safety Flashcards
What are the E’s of traffic safety?
Engineering, Education, Enforcement, EMS, Environment, Economics, Evaluation, and Everyone
Nominal Safety
meets minimum design criteria
Substantive Safety
actual safety performance of a roadway
How do highway features affect safety?
By influencing:
1. Driver ability to control the vehicle
2. Number of conflict points
3. Consequences of out-of-control vehicles
4. Ability of driver to select appropriate speed and path
The ideal highway is one with _________________________ over a section
uniformly high-quality design applied consistently
Key Safety Considerations
- Alignment and cross-section
- Sight distance
- Intersections
- Roadsides
- Signing and pavement markings
- Signals
- Pavement surface
Retroreflectivity
ability of a surface to return light to its source
An effective road safety management process consists of the following elements:
- crash records database
- network screening to identify crash locations
- diagnosis of sites and crash causing situations
- select appropriate countermeasures
- economic appraisal of improvements
- prioritize safety improvement projects
- evaluation effectiveness of implemented treatments
Are crash rates or frequency a better indicator of safety?
Rates - account for traffic volumes
How many years of crash data are desirable for analysis
3 years or more (as long as there haven’t been significant design or operations changes)
Collision Diagram
a schematic drawing that uses symbols to represent crash type
Condition Diagram
scale drawing, plan, or aerial photo showing all roadway features, including abutting land use, geometry, traffic control, etc.
How can potential countermeasures be identified?
- investigations of crashes to identify causal factors
- review site plan and condition diagrams
- site inspections
- traffic studies
- agency practices and previous experience
Safety Performance Functions
statistical base models for estimating average crash frequency for a specific site/facility type
function of AADT and segment length
Crash Modification Factors
ratio of the effectiveness of one condition in comparison to another condition
multiplied with crash frequency to account for difference between site and base conditions
Crash Reduction Factor
percentage of crashes that can be reduced/avoided by implementing an improvement
What two flaws are common when comparing before/after safety improvements?
Failure to control for the effects of changing conditions
Failure to correct for regression-to-the-mean
Road Safety Audit
a formal safety performance examination of an existing or future road or intersection by an independent audit team
What are the key elements of an RSA?
- formal examination with a structured process
- conducted independently by professionals not involved in the project
- completed by a team of qualified professionals representing appropriate disciplines
- focuses solely on safety issues
What are the steps of an RSA?
- select the team
- provide background info
- hold a commencement meeting
- assess documents
- inspect the site
- write the audit report
- hold a completion meeting
- designer/client response to the audit
- implement solutions
- close the loop
Traffic Calming
physical features that reduce the negative effects of motor vehicle use, alter driver behavior, and improve conditions for non-motorized street users
Principles of the Safe System Approach
- Deaths and serious injuries are unacceptable
- Humans make mistakes
- Humans are vulnerable
- Responsibility is shared
- Safety is proactive
- Redundancy is crucial
Safe System Elements
- Safe Road Users
- Safe Vehicles
- Safe Speeds
- Safe Roads
- Post-Crash Care
What are 3 key factors to reduce Kinetic Energy?
- Speed Reduction
- Reducing Conflict Angles
- Reducing Conflict Points
