Emergency Brake Display for
Rear End Accident Avoidance
Dr. J. Gail
Ressort „Active Vehicle Safety, Emissions, Energy“
Bundesanstalt für Staßenwesen
(Federal Highway Research Institute)
Bergisch Gladbach, Germany
Content
• requirements for an emergency brake
display
• examples
• optimum solution
• criteria for activation / deactivation
• regulations concerned
Dr. rer. nat. Jost Gail, Referat F1, Bundesanstalt für Straßenwesen
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Requirements for an
Emergency Brake Display (1)
•
•
•
•
fast perception (also by distracted drivers)
short reaction times
easy implementation and refitting
maximum deceleration of the following
car
• intuitive display (no learning necessary)
• few levels
Dr. rer. nat. Jost Gail, Referat F1, Bundesanstalt für Straßenwesen
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Requirements for an
Emergency Brake Display (2)
• threshold values corresponding to real
braking behaviour
• functionality for emergency braking on
low-µ-surfaces
• unambiguous display
• not confusing
• minimised effects of habituation
Dr. rer. nat. Jost Gail, Referat F1, Bundesanstalt für Straßenwesen
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Example 1: Increased Light
Surface Area and Intensity
1)
2)
Dr. rer. nat. Jost Gail, Referat F1, Bundesanstalt für Straßenwesen
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Increased Area and Intensity
• pros:
– intuitively
– no learning process
– causes adequate brakings of the following
driver (early maximum brake force)
– reduced reaction times
• cons:
– lights have to be fixed by the driver‘s eyes
– difficult refitting
– vehicle design
Dr. rer. nat. Jost Gail, Referat F1, Bundesanstalt für Straßenwesen
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Example 2: Integral Brakelight
3rd upper brakelight:
t1
G   a dt
3
G
t0
( 19 levels)
 too many levels
Dr. rer. nat. Jost Gail, Referat F1, Bundesanstalt für Straßenwesen
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Example 3: Flashing Brakelights
(flashing)
Dr. rer. nat. Jost Gail, Referat F1, Bundesanstalt für Straßenwesen
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Flashing Brakelights
reduction in reaction time: (source: DaimlerChrysler)
Effective Reaction Times with and without
Distraction
usual brakelights
usual lower brakelights +
flashing upper brakelight
without distraction
with distraction
0
0,5
1
1,5
2
2,5
Effective Reaction Time / s
Flashing Brakelights
• pros:
– good perception also by distracted drivers
– reduced reaction times
– easy refitting
• cons:
– learning process might be necessary
Dr. rer. nat. Jost Gail, Referat F1, Bundesanstalt für Straßenwesen
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Example 4: Flashing Hazard
Warning Lights
(flashing)
Dr. rer. nat. Jost Gail, Referat F1, Bundesanstalt für Straßenwesen
11
Flashing Hazard Warning Lights
reduction in reaction time: (source: DaimlerChrysler)
Effective Reaction Times with and without
Distraction
usual brakelights
usual brakelights + flashing
hazard warning lights
usual lower brakelights +
flashing upper brakelight
without distraction
with distraction
0
0,5
1
1,5
2
2,5
Effective Reaction Time / s
Flashing Hazard Warning Lights
• pros:
– good perception
– reduced reaction times
– easy refitting
• cons:
– change in colour
– usual meaning: warning in case of:
• broken down vehicle
• accident
• end of congestion
– automatical switching only if
deceleration > 1.5 g
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Example 5: Continuously Shining
Rear Direction-Indicators
• pros:
– easy refitting
• cons:
– change in colour
– meaning is not intuitively clear
Dr. rer. nat. Jost Gail, Referat F1, Bundesanstalt für Straßenwesen
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Optimum Solution (1)
• keeping the colour coding:
red light = braking
• flashing to achieve best perception by
distracted drivers
(3 Hz to 5 Hz flashing)
Dr. rer. nat. Jost Gail, Referat F1, Bundesanstalt für Straßenwesen
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Optimum Solution (2)
1)
• optional: increase in
surface area of lower
brakelights additional to
flashing upper brakelight
2)
(3 Hz - 5 Hz)
 best perception + intuitive display
for severe braking
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Criteria for Activation / Deactivation (1)
• threshold deceleration 7 m / s2
• emergency brake assistance system
• anti-lock brake system
• pressure of the brake system / brake
force
• change of vehicle velocity (real
deceleration)
Dr. rer. nat. Jost Gail, Referat F1, Bundesanstalt für Straßenwesen
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Criteria for Activation / Deactivation (2)
• switching on immediately after detection
of emergency braking
• switching off after
– releasing the brake pedal or
– after standstill of the vehicle or
– detection of the end of the severe braking by
a brake assistance / anti-lock braking system
• threshold velocity 5 km / h
Dr. rer. nat. Jost Gail, Referat F1, Bundesanstalt für Straßenwesen
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Regulations Concerned
ECE-R 7, ECE-R 48 and Vienna Convention
• red flashing upper brakelight
• increase in surface area
• definition of activation of brakelights
• changing display during braking
• fixing of switching criteria
Dr. rer. nat. Jost Gail, Referat F1, Bundesanstalt für Straßenwesen
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