Impact Speed and a Pedestrian’s Risk of Severe Injury or Death

Introduction

Based on the study of AAA  Foundation this post shares the summary of the original report that might be downloaded by the link below.

The data analyzed in this study were from the NHTSA’s National Automotive Sampling System (NASS)  Pedestrian  Crash  Data  Study  (PCDS)  (PCDS,  2008).  The  PCDS  compiled  data  from  on‐scene  and  follow‐up  investigations  of  crashes  that  occurred  in  Buffalo,  NY;  Fort  Lauderdale,  FL;  Dallas,  TX;  Chicago, IL; Seattle, WA; and San Antonio, TX from July 1994 through December 1998 and involved a  pedestrian struck by a forward‐moving car, pickup truck, van, or SUV (pickup trucks, vans, and SUVs  hereafter are referred to collectively as light trucks) with the first point of contact forward of the top  of  the  vehicle’s  A‐pillar.

The  sample  was  restricted  to  vehicles  manufactured  within  5  years  of  the  study period (model years 1989–1999). Crashes were excluded from the PCDS if the pedestrian was  sitting  or  lying  in  the  roadway,  the  striking  portion  of  the  vehicle  had  been  modified  or  damaged  previously,  the  vehicle  was  involved  in  other  impacts  besides  that  with  the  pedestrian,  or  vehicle  damage measurements were  not  obtained within  24  hours  of  the  crash.

The data  file contained 549  records  of pedestrians  struck by  vehicles. The  sample  analyzed  for  this  study  comprised  422  pedestrians  ages  15  years  and  older  who  were  struck  by  a  single  forward‐moving  car  or  light  truck  model  year  1989–1999  and  whose  injury  severity  was  known.

Summary

Adjusted for age, height, weight, BMI, and type of striking vehicle, and standardized to the distribution  of  pedestrian  age  and  type  of  striking  vehicle  for  pedestrians  struck  in  the  United  States  in  years  2007–2009, the average risk of severe injury reached 10% at an impact speed of 16 mph, 25% at 23  mph, 50% at 31 mph, 75% at 39 mph, and 90% at 46 mph. Risk of severe injury increased  approximately linearly with speed for speeds between 23 mph and 38 mph, with an average increase  of 3.2 percentage points (95% Confidence Interval [CI]: 2.7 – 3.8) for each 1 mph increase in impact  speed for speeds within this range.

The average adjusted, standardized risk of death reached 10% at an impact speed of 23 mph, 25% at  32 mph, 50% at 42 mph, 75% at 50 mph, and 90% at 58 mph. Risk of death increased approximately  linearly  with  speed  for  speeds  between  32  mph  and  50  mph,  with  an  average  increase  of  2.8  percentage points (95% CI: 2.2 – 3.4) for each 1 mph increase in impact speed for speeds within this  range. 

Graphs below demonstrate the abovementioned standardized risk of death / risk of severe injury relation to the impact speed.

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