Europe has long set the standard for rail travel, with a system whose efficiency, extent, and affordability has been the envy of rail advocates in the United States. But now it seems that European transportation trends are in danger of imitating those in the U.S: In the last decade, the highway network in the European Union grew by about 25 percent, to over 31,000 miles, while the rail network shrank by 4 percent, to around 95,700 miles. Those figures represent a challenge for the 15-country bloc, which hopes to reduce pollution and traffic congestion by boosting rail travel for both passengers and goods. Without such steps, the European Commission predicts that truck traffic alone will increase by 50 percent in the next 10 years.