In Virginia, the police periodically set up sobriety checkpoints with a roadblock and inspect random drivers for intoxication. There are a number of laws and procedures in Virginia that regulate how sobriety checkpoints work. One of the most important is that the location and time of the checkpoints must be announced to the public before the checkpoints are set up.
The police department usually announces these checkpoints on the “news" section of its website or in local newspapers and internet news sites. These locations are announced so that drivers can avoid the traffic problems caused by these checkpoints.
Another important rule about sobriety checkpoints is that the police cannot stop every car that approaches the checkpoint. Each car that is stopped is chosen by a mathematical formula (such as every fourth or fifth car). However, erratic driving, dangerous driving, or illegal driving may cause a person to be pulled over despite not being chosen to be stopped in the checkpoint.
The most common example is when a driver approaches a sobriety checkpoint, slows down, and then makes an illegal U-turn. The police can pull that driver over for an illegal U-turn. If the driver had executed a legal maneuver and was not driving illegally or dangerously, the police would not be able to stop him.
The final rule about sobriety checkpoints is that checkpoints must minimize the time that each driver is stopped. The officer cannot make you step out of your car or ask you to take any tests unless there are signs of impairment. These signs include the smell of alcoholic beverage on the breath, slurred speech, erratic driving, blood shot eyes, and other similar signs. If the driver does not exhibit any signs, the driver must be allowed to go. If the officer decides that the driver displays signs of impairment, he will be asked to pull over to a separate area where the officer will continue the investigation.