Final answer:
Crossing air lines on an old trailer without spring brakes can lead to brake failure and unsafe conditions. Trailers that bounce are likely empty since the lack of load allows for more movement. Tollbooth wires are for vehicle detection, and experiments could measure the effectiveness of loose gravel ramps for stopping trucks.
Step-by-step explanation:
When a driver crosses the airline while hooking up to an old trailer without spring brakes, this could potentially lead to brake failure. Spring brakes are designed to operate as a fail-safe for the trailer's braking system. If the lines are crossed, the trailer's brakes may not engage properly when the brake pedal is applied, leading to an unsafe condition where the trailer cannot be slowed or stopped as expected.
Regarding a trailer bouncing up and down slowly on the highway, it is more likely that the trailer is nearly empty. A heavily loaded trailer tends to have less bounce because the weight stabilizes it and dampens the motion. In contrast, an empty trailer lacks the mass to absorb the energy from bumps and dips in the road, causing more pronounced bouncing movements.
The piece of wire before tollbooth stations is often part of a sensor system to detect the approaching vehicle. This triggers the toll system to prepare for the vehicle, whether it's to prompt the driver for payment or to work with electronic toll collection systems.
An experiment to measure the effectiveness of loose gravel ramps for stopping semis with failed brakes in the Appalachians could be designed by using a controlled truck with adjustable braking capability. By simulating brake failure at varied speeds and loads, measuring stopping distances and the force exerted on the truck as it enters the gravel can yield data on the ramp's effectiveness. This experiment must adhere to strict safety guidelines to protect the experimenters and any other parties involved.