My team had a "passive" manipulator that was essentially two thick sheet metal tusks put together, lowered by a single pneumatic piston (we changed it from the original picture). This let us drive straight into the bridge without stopping, saving us precious time, but we were also able to lower the piston when the Joebot was right in front of the bridge, so it could be used "actively."
You might notice that the top of the tusks is very close to the edge of the bridge. Every once in a while, we encountered an issue with the tusks driving under the bridge and pushing it up.
