Motorists can travel without restriction across the United States. No identity papers, travel insurance papers, or other documents are required for intra- or interstate travel. The only drivers required to stop periodically are semi drivers who must have their trucks weighed at weighing posts. Besides border crossings where you must present identification and/or proof of citizenship, motorists may encounter roadblocks due to accidents or construction and sobriety checkpoints.
Sobriety checkpoints are essential police deterrents against drunken driving or driving while under the influence of drugs or alcohol. Many question the constitutionality and legality of such checkpoints and the ensuing privacy issues. Both state and federal courts have addressed the fourth amendment right against unreasonable search and seizure, but only the Supreme Court can interpret constitutionality of such checkpoints.
Every state in the United States classifies blood alcohol concentrations (BAC) to be legally impaired when it reaches 0.08 percent or above. At 0.05 percent the probability of fatality in an alcohol-related crash is significant. When it hits that 0.08 mark, probability will rise dramatically. The Insurance Institute for Highway Safety estimated in 2008 that 8,104 deaths might have been prevented that year if those people had BACs less than 0.08. This, in turn, may serve to bring down travel insurance policy costs.
The Center for Disease Control estimates that well-publicized and frequent sobriety checkpoints can reduce fatality between 18 to 24 percent. About one in 88 is arrested for driving over the 0.08 legal limit in the U.S. The main purpose of a sobriety checkpoint or roadblock is deterrence, not arrest. If you wish not to go through the checkpoint, simply find another route to your destination, as checkpoints must be announced well in advance. For those traveling through an area designated for a checkpoint, and if you are unfamiliar with the locale, and have no GPS to guide you around the checkpoint, simply approach and you will either be waved on or told to stop. Most drivers are through the checkpoint in a minute or two if there is no reason to detain you for further testing due to alcohol impairment.
Sobriety checkpoints must display checkpoint warning signs to motorists and vehicles are not stopped at random, but in a sequence of every fourth car or whatever number is designated ahead of time by law enforcement personnel setting up the site. Police cannot administer breath tests unless reasonably certain that the driver has been drinking.
Although the U.S. Supreme Court in Michigan vs. Sitz upheld the constitutionality of sobriety checkpoints, state courts in Alaska, Idaho, Iowa, Michigan, Minnesota, Oregon, Rhode Island, Texas, Washington, Wisconsin, and Wyoming found that conducting sobriety checkpoints or roadblocks are illegal. All 39 other states can legally conduct sobriety checkpoints. The Insurance Institute for Highway Safety’s Highway Loss Data Institute lists each state court decision and its citation on their web site.