This may be the largest and busiest railway yard in the world, where more than half of Union Pacific's rail traffic passes through at some point. Throughout the 150 parallel tracks at the 8 mile long yard, trains are assembled, reconfigured, and loaded at a rate of around 120 trains and 9,000 freight cars per day. In addition, maintenance facilities repair locomotives and railcars at the yard. The yard is a popular spot for Railfans who can watch for the numbered locomotives from a special visitors platform that offers a view of the yards. The visitation facilities may improve soon, with the creation of a proposed visitor's center. The planned building would have gift shops, interactive and static displays, and a 15 story observation tower in the shape of a golden spike. Due to the volume and diversity of goods handled at the yard, its activity is apparently a responsive barometer of the overall economic condition of the nation.