validation of the step theory
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13/9/12 1
Validation of the Step Theory
E.C.M. Kroon Master Thesis TIL
Witteveen+Bos
Rijkswaterstaat
TU Delft
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Index
n Introduction to the Step Theory n Literature Study n Methods n Driving simulator Study n The challange of a literature study
INTRODUCTION TO THE STEP THEORY
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Step Theory
n Design speed of successive road elements should decrease gradually 120 km/h - 100km/h - 80km/h - 50 km/h
n Goal: facilitate a safe transition in operational speed, by road design only
Q1
Q2
Figuur 1, Haarlemmermeeraansluiting
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Step Theory in practice
n Speed Q1 is multiple steps lower ¨ Krappe bocht door beperkt ruimtebeslag is geaccepteerd. Extra
aandacht voor compenserende maatregelen
n Speed between Q1 en Q2 differs multiple steps
n Speed of Q2 does not connect with the underling road network
n Q1 en Q2 are separated by a short road section, by which operational speeds at Q2 become too high
n It is unclear whether the deceleration lane can be seen as a full step
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Main goal
n Validation of the Step Theory To which extend does the step theory contribute to traffic safety at ramps and F-F connectors on Dutch motorways?
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Subquestions n What is the underlying basis of the step theory and is there literary
support for it? n Is there a difference in speed profiles for the degree in which the
step theory is applied? n Is there a difference in traffic safety for the degree in which the
step theory is applied? n Is there a difference found between road types in relation to the
degree in which the step theory is applied, measured in speed and crash rate?
n Is there a difference found between road configurations in relation to the degree in which the step theory is applied, measured in speed and crash rate?
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Research setup
LITERATURE STUDY
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Subquestions
n What is the underlying basis of the step theory and is there literary support for it?
n Which independent factors are of influence on operational speeds and traffic safety in motorway curves as well?
n Which road configurations are of interest for this study?
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Conclusies [1]
n Hardly any studies towards deceleration behaviour at motorways
n Consistency theories on step size exist, though there is no hard validation
n Consistency indicators, like: ¨ Variability in speed Crash rate ¨ Workload, hart rate variability Road position
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Conclusies [2]
n Factors to take into account when analysing curves, like: ¨ Curve length ¨ Curve-tangent-curve ¨ Road signs
n Deceleration behaviour on deceleration lanes is likely to be dependent on the first curve radius
n No literature on differences between connector roads and ramps
n Configurations ¨ No curve-tangent-curve
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METHODE
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General setup
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Variables
n Stepsize n Configuration n Road type
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Indicators crashstudy
n Crashes
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Indicators Driving simulator [1]
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Indicators Driving simulator [2]
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n Smoothness
Indicators Driving simulator [3]
n Calculating smoothness ¨ Standerdize over time – absolute difference over time
step – summation to obtain one value
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DRIVING SIMULATOR STUDY
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Limitations driving simulator
n No hights ¨ No interchange
n No superelevation
n Difference between ramp and connector road difficult to simulate
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Setup
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Map
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Population
n 45 participants n 71% man vs. 29%
woman
n 3 became motion sick n 4 other dropouts
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Age distribution
0123456789
10111213141516
<25 26-‐30 31-‐35 36-‐40 41-‐45 46-‐50 51-‐55 56-‐60 61-‐65
Age of participants [years]
Num
ber o
f participants [#
]
Distribution of driving experience
0
2
4
6
8
10
12
14
0-‐5 6-‐10 11-‐15 16-‐20 21-‐25 26-‐30 31-‐35 36-‐40 41-‐45
Possession of driving license [years]
Num
ber o
f participants [#
]
n Speed n Lateral position
Results [1]
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Results [2]
n Steering angle n Lateral speed
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Results [3]
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THE CHALLENGE OF A LITERATURE STUDY
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Where to start?
n Quickly gain a broad perspective on your topic
n Set clear goals n Structure your literature study and think of
how to present your output
n Reassess halfway!
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For what purpose?
Determining n Variables n Indicators n Scope n Methods n Oppertunities
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Assess literature
n Method used in paper n Population n Experimental conditions n Significance
n Be critical!
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Perform your literature review properly and you will be one step ahead of your committee
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QUESTIONS
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