Regulation of Speed in Car Following

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Regulation of Speed in Car Following

• George J. Andersen
• Craig Sauer
• Asad Saidpour
• Department of Psychology
• University of California, Riverside

PATH Project MOU 4220
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Utility of Human Driver Model

• Warning Systems
• Autonomous/semi-autonomous Vehicle Control
• Traffic Flow Models

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REACT Collision Detection Model

• Model based on analysis of visual information
  available to driver
• Use of 5 parameters
• t
• dt/dt
• a
• da/dt
• ddiff

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t specifies the time to contact during constant
velocity collisions
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dt/dt used during deceleration When dt/dt -0.5
vehicle will reach zero velocity at obstacle
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a is the position of object in visual field
When a 0 object is on a collision path Useful
when path of motion is linear
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da/dt is the change in position of object in
visual field
When da/dt approaches zero object is on a
collision path Useful when path of motion is
curvilinear
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ddiff is comparison of two distance estimates dv
distance vehicle will traverse before reaching
zero velocity ds distance of collision object
ddiff dv ds dv 1.5v2/a v number of
texture elements that pass position in visual
field a change in number of texture Elements
that pass position in visual field ds (s)tan-1
q s size of object q visual angle of object
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Vehicle Motion
No
F/S
V/S
F/C
V/C
No
F/S
Object Motion
V/S
F/C
V/C
F Fixed Speed V Variable Speed S Straight
Path C Curved Path
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Select Object
Derive a, d?/dt (angular direction)
Is a0? Or d?/dt?0?(constant angular direction)
Yes
No
Derive t
Is tgt0? (expansion)?
Derive dt/dt
Derive dv-ds
Yes
Is dt/dt 0? (Constant expansion)
Is dv-ds 0? (Constant expansion)
Yes
Collision Object
No
No
Is dt/dt gt-0.5?
Is dv-ds gt0?
Yes
No
Non-collision Object
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Can parameters of REACT be used for car following?
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Limitations of REACT Parameters

• t, dt/dt, and ddiff only useful when a collision
  is impending
• a and da/dt only useful for recovering collision
  path information

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Optical Information for Car Following

• Information for specifying distance and change in
  distance
• Information for specifying speed and change in
  speed

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Dq associated with change in distance due to
change in speed
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Parameters of Car Following Model

• q0
• Initial visual angle on target vehicle
• q
• Current visual angle
• dq/dt
• Instantaneous change in visual angle
• k1, k2
• Constant determined by small or large velocity
  change

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How is change in speed determined?
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Human Factors Experiments

• Maintain distance behind target vehicle that
  varied speed
• - sine function
• - ramp function

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Conclusions

• Presented a model of car following
• Based on visual angle information of target
  vehicle
• Performance of model good fit to performance of
  drivers in car following study
• Examining role of speed information from
  surrounding scene