Braking Distance

Written by Jerry Ratzlaff on . Posted in Civil Engineering

stopping distance 1Breaking distance, abbreviated as \(B_d\) , is the distance that a vehical travels while slowing to a complete stop.

 

Braking Distance formulas

\(\large{ B_d = 1.075 \; \frac{ V^2  }{ a }  }\)  
\(\large{ B_d =  \frac{ 1.075 \; V^2  }{ a }  }\)  

Where:

\(\large{ B_d }\) = braking distance

\(\large{ a }\) = deceleration rate

\(\large{ V }\) = design speed

 

AASHTO Exhibit 3-1 Stopping Sight Distance

 Design Speed 
 

 Brake Reaction 

Distance

 

 Braking Distance 

on Level

 

Stopping Sight

Distance 

 Calculated       Design   
 15  55.1  21.6 76.7  80
 20  73..5  38.4  111.9  115
25 91.9  60.0  151.9 155
30 110.3  86.4 196.7 200
35 128.6  117.6  246.2 250
40 147.0  153.6 300.6 305
45 165.4  194.4  359.8 360
 50  183.8  240.0 423.8  425
55 202.1  290.3 492.4 495
60 220.5  345.5 566.0 570
65 238.9  4.505 644.4 645
70 257.3  470.3 727.6 730
75 275.6  539.9 815.5 820
80 294.0  614.3 908.3 910

Note:  Brake reaction distance predicated on a time of 2.5 s; deceleration

rate of 11.2 \(ft/s^2\) used to determine calculated sight distance.

 

 

Tags: Equations for Transportation