Union Pacific's service record has been a debacle since it bought Southern Pacific Rail Corp. last year in a huge industry consolidation. UP's terminal near L.A. is presently badly backed up, and the company is losing business. Moreover, three fatal accidents in as many months have brought federal safety investigators into the picture. Now, the STB will be trying to show it is more than an industry rubber stamp, and CSX and NS will be under even more intense pressure to show what their merger will do for, rather than to, the diverse constituencies now weighing in on their merger plans.