Despite a spluttering global economy, BNSF and Union Pacific are continuing to invest heavily to increase capacity on two of their major transcontinental corridors. For BNSF, the priority for 2011 has been the unplugging of Abo Canyon in New Mexico, a single-track bottleneck on its former Santa Fe Chicago -- Los Angeles 'Transcon' main line. Meanwhile, Union Pacific is continuing its huge programme to double-track the former Southern Pacific Sunset Route between El Paso and Los Angeles.

One route penetrates the heart of the Midwest, and the other skirts the country's southern border, but it is no coincidence that both have Southern California as their western terminus. With intermodal traffic booming, propelled by a shift of manufacturing to Asia and the associated rise in imported goods, there has been a 280% increase since 1996 in both imports and exports through the twin ports of Long Beach and Los Angeles, which are the busiest ports on the US west coast. Port throughput is expected to continue growing rapidly in the future, and both railroads are keen to capture a larger percentage of the business as the global market comes out of recession.

Whilst overall tonnage from and to other Pacific Rim nations is down from the record highs seen a few years ago, the market is recovering, and both railroads know it. Preparing for the traffic demands that will inevitably return, BNSF and UP have been taking advantage of the comparative lull in traffic to beef up and clear the chokepoints on their respective routes.

Unblocking Abo Canyon

When the Atchison, Topeka & Santa Fe Railway completed its original transcontinental route between Chicago and Southern California in the 1880s, the alignment included a tortuous crossing of Raton Pass on the Colorado-New Mexico border, where steep grades led to slow speeds and the use of helper engines. A second line further south, known as the Belen Cutoff, was completed in 1908, replacing the 3-5% gradients of Raton Pass by a more gentle route with a steepest grade of 1-25%. This is now BNSF Railway's Transcon -- a largely double-track 110 km/h freight artery that hosts close to 100 trains a day.

BNSF has been steadily upgrading the Transcon for almost two decades, but one challenge remained. About 80 km south of Albuquerque, New Mexico's 8 km--long Abo Canyon posed a perennial operating headache, with trains winding around 100 m high bluffs, through cuttings up to 45 m deep, and over high bridges. For 100 years, the tortuous alignment made a second track just a dream. But, with train numbers increasing and the demands of 21st century intermodal shippers, BNSF felt it was finally time to do something about the long-time bottleneck. In 2004 it began work on an $85m project which eventually took seven years to complete.

While other BNSF double-tracking projects along the Transcon -- including almost 320 km through Texas -- were important, the taming of the tough, unyielding terrain of Abo Canyon would be the biggest psychological high for...