Tunnels are our Transportation Future
Cheap tunnels can significantly improve the throughput of our transportation systems. To understand how, let's overview freight trains, passenger trains, trucks, cars, and tunneling technology.
Rolling resistance is primarily from the deformation of wheels as they roll over the ground. Rubber tires have more rolling resistance than steel wheels. Rolling resistance scales linearly with the weight of the vehicle. Speed has little effect.
The rolling resistance coefficient changes based on wheel diameter, type of material, and the weight on the wheel. Steel railroad wheels have their coefficient decrease with higher loads. Rubber tires do not usually have the same advantage.
Trains with heavy loads traveling at moderate speeds are much more fuel-efficient than trucks because their steel wheels reduce rolling resistance. If we compare two high-speed, lightweight vehicles, drag dominates. Whether they use tires or rails has less impact on efficiency.
Trucks are much more flexible than trains because they can haul smaller loads and have access to the road network. Goods arrive faster on trucks. Trains transport large, heavy loads long distances. As a result, trains haul 40% of ton-miles but only 15% of freight value.
