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
