approval. A large number of expressways are actually government or privately operated toll roads in many East Coast and Midwestern states. West Coast freeways are generally free to users ("freeways", no toll charged per use), although since the 1990s there have been some small experiments with toll roads operated by private companies. After the collapse of the I-35W Mississippi River bridge in Minnesota in August 2007, the backlog of road and bridge maintenance across the country became an issue in transportation funding. The collapse prompted a tax increase in Minnesota to speed up bridge repairs, and action in other states, such as the Accelerated Bridge Program in Massachusetts, but after some debate no increase in federal funding. The 2013 I-5 Skagit River Bridge collapse, caused by a collision with an over-height truck, highlighted "fracture critical" bridges in which the failure of only one structural member will lead to complete collapse. According to the National Bridge Inventory, there are at least 600,000 bridges of 20 feet or more in length in the United States, all subject to deterioration in the absence of preventative maintenance. In December 2008, 72,868 bridges in the United States (12.1%) were categorized as "structurally deficient", representing an estimated $48 billion in repairs. President Barack Obama proposed $50 billion of spending on road and bridge repair, plus a national infrastructure bank, but Congress did not act on these proposals. President Donald Trump also failed to get infrastructure funding approved. In 2021, President Joe Biden signed a bipartisan infrastructure bill with about $110 billion for roads and bridges. As of 2010, seat belt use is mandatory in all states except New Hampshire. Seat belt use is also mandatory in the District of Columbia and the five inhabited U.S. territories. Intercity bus Greyhound Lines is the largest intercity bus company in the United States, with routes in all parts of the contiguous U.S. There are also many smaller regional bus companies, many of which use the terminal and booking facilities provided by Greyhound. Intercity bus is, in most cases, the least expensive way to travel long distances in the United States. Congestion Traffic congestion, especially at rush hour, is often considered a problem in many of the country's larger cities. A 2009 study claimed that traffic congestion costs the United States almost $87.2 billion. The economic costs of traffic congestion have increased 63% over the past decade, and despite the