The worry was that a terrorist could use a large tractor-trailer truck to take down a bridge by filling it with explosives and detonating it either near the anchor points for a suspension bridge's cables, or on the bridge itself. Especially worrisome are the seven bridges across the San Fransico Bay.
So California authorities asked <a href="http://www.llnl.gov">Lawrence Livermore Lab</a> scientists to see if they could come up with anything. Consultant Bill Wattenburg came up with the "Truck Stopping Device", which just uses the normal brakes of the truck to stop it.
You can read more about it here: <a href="http://www.llnl.gov/llnl/06news/Employee/articles/2001/11-30-01-truck.html">
http://www.llnl.gov/llnl/06news/Empl...-01-truck.html</a>
And there's more here including a video of it in action: <a href="http://www.chp.ca.gov/html/truckstoppingdevice.html">
http://www.chp.ca.gov/html/truckstoppingdevice.html</a>
They didn't mention a lot about practical jokers setting this thing off. They did have this to say, though:
<blockquote>
In case of accidental deployment, truck drivers can repair or reset the device to normal operating position in about 15 minutes. However, this cannot be done from within the truck’s cab. The driver would be required to leave the cab and walk to the rear of the truck, allowing law enforcement access to the driver.
</blockquote>
I'm skeptical that we'll see people ramming their cars into trucks just to see this go off. They'd pretty much kill their own cars, thus giving themselves up the in process. I think things like this would land them in the "stupid criminal" bin.