A closer look
Despite their monstrous diesel-electric horsepower, trains are defeated by mild geographic inclines. The efficiency of a train relies entirely on smooth steel wheels rolling effortlessly over smooth steel rails, which practically eliminates rolling resistance. The glaring downside is a near-total lack of grip. If a freight train tries to climb a gradient steeper than 2%, the wheels just spin helplessly in place. Mountains basically force railway engineers to blast holes through solid rock.
