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)
2
Q
A