Mechanical-Arrester Escape Ramps

Mechanical-arrester escape ramps involve one or many steel nets that catches the truck and slows it down rapidly. This method is used where there is little space for a truck ramp because the nets are so effective. However, these nets can be expensive to maintain. Every time a truck uses the ramp, the net has to be reinstalled. A mechanical-arrester ramp in Avon, Connecticut even has electric heated pavement, which cost $400,000 alone in addition to the $2.8 million ramp (Hanley).

fig. 5 A mechanical-arrester escape ramp

The Physics

    The resisting force is the nets, which can be modeled as a spring force. According to the spring force equation: F=-kx, the force increases exponentially with the distance which allows the truck to stop so fast. Also, the heated ramp increases the rolling friction.

Given that this particular mechanical-arrest ramp is 330ft long (Hanley) and a design for a 100,000lb truck entering the ramp at 103ft/s (70mph) we can calculate the spring constant of the nets. $\mathrm{}$

$To\; find\; the\; required\; acceleration\; to\; stop\; the\; truck\; in\; 330ft\; we\; use\; the\; equation:$

$$a(s_0-s_1)=(v_2^2-v_1^2)/2$$

And by using Newton's Second Law we are able to find the spring constant