3A. Forgiving roadside concepts Flashcards

(e.g., clear zone, recoverable slopes, roadside obstacles)

1
Q

EstimatingSpeedofVehiclefromSkidMarks

A

P.E. Handbook 5.1.4.3

db =((v1)^2-(v2)^2) / (30 (f +-G))

db=horizontaldistancetraveled(ft)inreducingspeedofvehiclefrom v1tov2duringbrakingmaneuvers
v1=vehiclespeedwhenbrakesareapplied(initialspeed)(mph)
v2=vehiclespeedatendoftravel(finalspeed)(mph)
f=a/g =coefficient of friction (unitless) between tires and road pavement
a=decelerationofvehiclewhenbrakesareapplied(ft/sec2)
g=accelerationduetogravity(32.2ft/sec2)
G=gradeofroadway(decimalform;negativeifdownhill)

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