What is the restriction on speed through truss bridges when transporting loaded cars?

When transporting loaded cars, the restriction on speed through truss bridges is 10 mph. This lower speed limit is implemented primarily to ensure the safety and structural integrity of truss bridges, which can be more sensitive to dynamic loads and vibrations caused by the weight of loaded cars. Truss bridges are specifically designed to handle certain weight limits and forces, and excessive speed can increase the risk of structural failure or significant wear on both the bridge and the rolling stock.

The choice of 10 mph reflects a precautionary approach that prioritizes safety, particularly given the unique engineering characteristics of truss bridges. It is essential for operators and crew members to adhere to this speed limit to mitigate risks associated with the transporting of heavy loads.