Emergency Brake Display forRear End Accident AvoidanceDr. J. Gail

Ressort Active Vehicle Safety, Emissions, Energy

Bundesanstalt fr Staenwesen(Federal Highway Research Institute)Bergisch Gladbach, Germany

Contentrequirements for an emergency brake displayexamplesoptimum solutioncriteria for activation / deactivationregulations concerned

Requirements for anEmergency Brake Display (1)fast perception (also by distracted drivers)short reaction timeseasy implementation and refittingmaximum deceleration of the following carintuitive display (no learning necessary)few levels

Requirements for anEmergency Brake Display (2)threshold values corresponding to real braking behaviourfunctionality for emergency braking on low--surfacesunambiguous displaynot confusingminimised effects of habituation

Example 1: Increased Light Surface Area and Intensity

Increased Area and Intensitypros:intuitivelyno learning processcauses adequate brakings of the following driver (early maximum brake force)reduced reaction timescons:lights have to be fixed by the drivers eyesdifficult refittingvehicle design

Example 2: Integral Brakelight3rd upper brakelight: too many levelsG( 19 levels)

Example 3: Flashing Brakelights

Flashing Brakelights reduction in reaction time: (source: DaimlerChrysler)

Diagramm1

1.51.32

21.73

with distraction

without distraction

Effective Reaction Time / s

Effective Reaction Times with and without Distraction

Tabelle1

with distractionwithout distractionwith distractionwithout distraction

1.51.321.51.32

usual brakelights + flashing hazard warning lights1.751.5usual brakelights21.73

usual brakelights21.73

Tabelle1

with distraction

without distraction

Effective Reaction Time / s

Effective Reaction Times with and without Distraction

Tabelle2

with distraction

without distraction

Effective Reaction Time / s

Effective Reaction Times with and without Distraction

Tabelle3

Flashing Brakelightspros:good perception also by distracted driversreduced reaction timeseasy refittingcons:learning process might be necessary

Example 4: Flashing Hazard Warning Lights

Flashing Hazard Warning Lightsreduction in reaction time: (source: DaimlerChrysler)

Diagramm2

1.51.32

1.751.5

21.73

with distraction

without distraction

Effective Reaction Time / s

Effective Reaction Times with and without Distraction

Tabelle1

with distractionwithout distractionwith distractionwithout distraction

1.51.321.51.32

usual brakelights + flashing hazard warning lights1.751.5usual brakelights21.73

usual brakelights21.73

Tabelle1

with distraction

without distraction

Effective Reaction Time / s

Effective Reaction Times with and without Distraction

Tabelle2

with distraction

without distraction

Effective Reaction Time / s

Effective Reaction Times with and without Distraction

Tabelle3

Flashing Hazard Warning Lightspros:good perceptionreduced reaction timeseasy refittingcons:change in colourusual meaning: warning in case of:broken down vehicleaccidentend of congestionautomatical switching only if deceleration > 1.5 g

Example 5: Continuously Shining Rear Direction-Indicators pros: easy refitting cons: change in colour meaning is not intuitively clear

Optimum Solution (1)keeping the colour coding: red light = brakingflashing to achieve best perception by distracted drivers

(3 Hz to 5 Hz flashing)

Optimum Solution (2)optional: increase in surface area of lower brakelights additional to flashing upper brakelight1)2)(3 Hz - 5 Hz) best perception + intuitive display for severe braking

Criteria for Activation / Deactivation (1)threshold deceleration 7 m / s2emergency brake assistance systemanti-lock brake systempressure of the brake system / brake forcechange of vehicle velocity (real deceleration)

Criteria for Activation / Deactivation (2)switching on immediately after detection of emergency brakingswitching off afterreleasing the brake pedal orafter standstill of the vehicle ordetection of the end of the severe braking by a brake assistance / anti-lock braking systemthreshold velocity 5 km / h

Regulations ConcernedECE-R 7, ECE-R 48 and Vienna Conventionred flashing upper brakelightincrease in surface areadefinition of activation of brakelightschanging display during brakingfixing of switching criteria