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1. 4 December 2008 / Analysis of black spots Step 2: Executing analysis Trace common characteristics
Start analysis with manoeuvre work sheet:
accident type
location of accidents
Which type or characteristic is dominant ?
Dominant? Five or more accidents:
no statistical criterion, practical indication
depends on total number of accidents
2. 4 December 2008 / Analysis of black spots
3. 4 December 2008 / Analysis of black spots Step 2: Execute analysis Accidents not in a dominant group, leave out of analysis
Common characteristics within dominant group(s)
Accidents of different natures can have same causes
Use of percentages is not advised:
75% occur in the dark !
3 of 4 accidents occur in the dark !
Use worksheets:
time table
analysis overview
4. 4 December 2008 / Analysis of black spots
5. 4 December 2008 / Analysis of black spots
6. 4 December 2008 / Analysis of black spots Step 2/3: work sheet analysis overview
7. 4 December 2008 / Analysis of black spots Step 2: Execute analysis Question and answer technique:
does the similarity have any significance?
what conclusion can be drawn from this?
Are the conclusions relevant?
50% of accidents on a wet road? Relevant?
Need of reference data to interpret
8. 4 December 2008 / Analysis of black spots Step 2/3: Analysis overview
9. 4 December 2008 / Analysis of black spots Step 3: formulate hypotheses Each dominant accident type or characteristic
Compare conclusions after analysis:
contradictory
complementary
Hypothesis based on total view of the analysis of each dominant group
To hold connecting thread absolutely essential:
use work sheets
10. 4 December 2008 / Analysis of black spots Step 3: formulate hypothesis
11. 4 December 2008 / Analysis of black spots Step 4: test hypotheses Site visit on base of hypotheses:
hypothesis is right
hypothesis is wrong
No statistical testing! Experience /knowledge!
Researcher should image himself in accident circumstances as much as possible:
means of transport
day / time of day
light and weather circumstances
Attention for approaching the location, lay-out, behaviour, attention level of road users, .
12. 4 December 2008 / Analysis of black spots Step 4: test hypotheses List with points of particular interest
Observations of behaviour is very important:
approach speed
brake / stop behaviour
head movements driver
accelerating / decelerating
Test the design against the guidelines is not the most important issue
Take pictures and / or video
13. 4 December 2008 / Analysis of black spots Method for road sections and areas (MADA) Method based on function, form and use
Functions (intended and in reality) per type of road user
pedestrians
cyclists
cars
The elements function, form and use must be tuned to one other
Method is more or less overruled by the concept of sustainable safety
14. 4 December 2008 / Analysis of black spots Analysis accident process What kind of accidents do you expect regarding the road functions:
hypothecally accident characteristics
Compare hypothecally accident characteristics with the dominant characteristics of recorded accidents
Determine accidents causes
15. 4 December 2008 / Analysis of black spots Step 4/7: Analysis overview
16. 4 December 2008 / Analysis of black spots Step 5: supplementary research Insufficient indications accidents cause(s):
stop the analysis
supplementary research
Possibilities
police reports of the accident
interview involved persons or road users
conflict observations
observations of behaviour (using models)
17. 4 December 2008 / Analysis of black spots Step 6: Establish accident causes Establishing or rejecting hypotheses
Establish each hypothesis accident cause(s)
Compare the various findings:
contradictory
complementary
Based on total view draw conclusions
Use work sheets
18. 4 December 2008 / Analysis of black spots Measure: restricting visibility
19. 4 December 2008 / Analysis of black spots Measure: drawing pin
20. 4 December 2008 / Analysis of black spots Measure: plateau
21. 4 December 2008 / Analysis of black spots Step 7: determine measures Measures:
infrastructure
education
enforcement
Tune measure to road function
Measure should eliminate the (assumed) causes
Establish side-effects
Take into account guidelines
22. 4 December 2008 / Analysis of black spots Measure example
23. 4 December 2008 / Analysis of black spots In practice
24. 4 December 2008 / Analysis of black spots Recapitulation Systematic analysis accidents:
five work sheets
Search for common factors: dominant groups
To draw conclusions from common characteristics for improving the design or use of the location
Connecting thread:
? all accidents
..?
? dominant type or character
.?
? conclusions analysis
.?
? hypothesis
.?
? establish causes
....?
? measure
..?
Experience with and knowledge of accident analysis is desired
25. 4 December 2008 / Analysis of black spots Content Black spot analysis
26. 4 December 2008 / Analysis of black spots What to do tomorrow ?