2002 SAE govt/Industry meeting
Jeff Woods presentation - NCAP Braking


SLIDE 1:
NCAP BRAKING
CONSUMER BRAKING INFORMATION
- Jeff Woods, NHTSA Safety Performance Standards


SLIDE 2:
INTRODUCTION
Concerns about developing brake system rating focus on variability of:
 - vehicle
 - test driver
 - test surface


SLIDE 3:
PROGRAM SUMMARY
1998-1999: Initial testing at Aberdeen test center
2999-2000: Round-robin testing at Aberdeen, MGA, TRC
2002:  Additional research on pedal force, pavement friction, statistics	


SLIDE 4:
1998 ABERDEEN TEST PROGRAM
Objectives:
- test a variety of light vehicles
- limit test conditions to reduce variability
- use only ABS-equipped vehicles
- perform statistical analyses of stopping distance results

SLIDE 5:
VEHICLES TESTED

10 ABS-Equipped vehicles
- 5 passenger cars (including control vehicle)
- 2 minivans
- 1 sport utility vehicle
- 1 full size van
- 1 full-size pickup (rear wheel only ABS)


SLIDE 6:
VEHICLE TEST CONDITIONS
- straight line stops
- dry asphalt
- wet asphalt
- test speed: 100 km/h (62mph)
- loaded and unloaded conditions
- 10 stops per test condition


SLIDE 7:
TEST RESULTS
- pedal forces higher than targed (112lbs) by 3X
- higher pedal forces did not affect stopping distance results
- rate of pedal application seems most important
- on control vehicle:
	* shortest stop: 139 ft w/237 lbs pedal force
	* longest stop: 150 ft w/309 lbs pedal force

SLIDE 8:
STATISTICAL ANALYSIS METHOD	
- average of 10 braking stops

- standard deviation

- 95th percentile: 95% of the time vehicle would stop within this distance. also measures stopping performance consistency


SLIDE 9:
TEST SURFACE PFC
- dry asphalt PFC: 0.89 - 0.95
- wet asphalt PFC: 0.85 - 0.88
- variability low, magnitude high
- PFC measured with skid trailer using:
	* ASTM Method EW1337-90
	* ASTM E1136 standard reference test tire


SLIDE 10:
VARIABILITY OF PFC
Peak Friction Coefficient [line graph]


SLIDE 11:
TEST PROGRAM
- further evaluate the effects of surface variability
- 4 vehicles tested at 3 different test sites, and again at first site
- surface friction measured at each site during testing
- analyzed and compared vehicle stopping distance performance at each test site


SLIDE 12:
1999 ROUND-ROBIN TESTING
Results Summary
- PFCs are different at each test track
  * some wet surfaces have friction as high as some dry surfaces
  * TRC had "ideal" PFCs, Aberdeen and MGA had rougher pavements due to weathering and little use

- brake application rate is important - 100lbs in0.2 seconds is achievable


SLIDE 13:
NON-ABS VEHICLES
problems with testing non-ABS vehicles:
 - stopping distance is dependent on driver skill
 - driver brake pedal modulation results in larger deviations between test runs
 - these stopping distance values may be less useful to consumers if they can't obtain similar real-world performance


SLIDE 14:
DRAFT TEST PROTOCOL

- ABS-equipped vehicles only
- test surface
  * dry PFC 0.90-0.95
  * wed PFF 0.80-0.85 (water depth =/< 3mm)
- loading: lightly-loaded wieght with 180 kg
- pedal force - 500 newtons in 0.25 sec
- number of stops - 10 per vehicle
- surface temperature:
  * dry: 25-45 degrees C (77-113 degrees F)
  * wet: 22-32 degrees C (72-90 degrees F)
- data: average and/or 95th percentile


SLIDE 15:
US/JAPAN TEST CONDITIONS COMPARISON

U.S. NCAP RESEARCH
- test speed: 100 km/h
- lane width: 3.7 m
- IBT: >/= 65 degrees C, </= 100 degrees C
- transmission: in gear
- pedal force: 500 N in 0.25 sec.
- number of stops: 10
- 180 kg load

JAPAN NCAP
- test speed: 100 km/h
- lane width: 3.5 m
- IBT: >/= 65 degrees C, </= 100 degrees C
- transmission: in neutral
- pedal force: 500 N in 0.25 sec.for ABS
- number of stops: 5
- 110 kg load



SLIDE 16:
ROAD SURFACE CONDITIONS COMPARISON

US NCAP RESEARCH
- Dry PFC 0.90-0.95
- web PFC 0.80-.085
- water depth: </= 3mm
- PFC measured using ASTM 1337-90 with SRTT ASTM 1136.93
- specify surface temperature

JAPAN NCAP
- surface specified as a flat, clean, asphalt-paved road
  * dry road surface, temperature of 25-45 C
  * wet road surface, temperature of 22-32 C

SLIDE 17:
TEST SITE ISSUES
- NHTSA's VRTC East Liberty, Ohio track - winter testing issues
- NHTSA's San Angelo, Texas UTQG facility is speed limited, dedicated to tire testing
- NHTSA is not identifying potential test sites. No contract action as of this time.
  * contract testing of NCAP vehicles
  * available to vehicle manufacturers

SLIDE 18:
REQUEST FOR COMMENTS
- RFC Notice published July 17, 2001. Closing date October 15, 2001
- public meeting was cancelled
- view all materials at:
  * http://dms.dot.gov
  * Docket No. 6583

SLIDE 19-24:
SUMMARY OF COMMENTS
- PFC - specified range would result in 5% to 6% variation in stopping distance
  * better to have a target PFC
  * 1 recommendation to correct stopping distance for PFC
  * 1 recommendation for 0.5 web PFC
  * generally, all recommend one test site

- Wet PFC
  * close to dry PFC, will not produce much longer stopping distances
  * NHTSA believes that the lower the PFC, the greater the variability
  * some suggestions to review skid numbers in addition to PFC

- Brake pedal application criteria
  * some recommend 500 N be attained in 0.15 second instead of 0.25
  * trigger stop using >0 pedal force instead of stop lamp switch
  * some recommend 500 N steady-state pedal force instead of 670 N

- Vehicle Loading
  * some recommend GVWR tests in addition to LLVW

- Non-ABS Vehicles
  * some recommend testing them as well, driver best-effort
  * stopping distance and stability important to convey to consumers

- Reporting results
  * many recommend average instead of 95th percentile
  * one recommends shortest stop
  * most recommend bar graph (JNCAP), no support for star ratings
  * recommendation to perform research in this area

- Recommendation that safety benefits (crash avoidance, likelihood of injury/fatality) be related to stopping distance


SLIDE 25:
ADDITIONAL TESTING - 2002
- investigate pedal force application criteria (ramp-up and steady-state) to finalize
- additional statistical reivew of stopping distance data
- continue pavement friction testing and evaluating variability



SLIDE 26:
FUTURE TESTING
- Identify test site to conduct NCAP braking program
- investigate methods of wetting test surface
- finalize wet and dry PFC values
- run pilot test program

SLIDE 27:
NHTSA and JNCAP	
- Visit the NHTSA website at www.nhtsa.dot.gov
- JNCAP results at www.osa.go.jp