Cops typically do not arrest people for speeding or other minor traffic violations in Nevada unless they are going excessively fast, they are endangering others, or they have outstanding warrants.
The most common reason people get arrested at a traffic stop is because the cop ran their names and found outstanding warrants. In those cases, cops are required to take the person into custody. Within a couple of days the arrestee will go in front of the judge, and the underlying criminal case will resume.
Many people who are arrested on outstanding warrants in Nevada have no idea they had a warrant to begin with. Often judges issue warrants on people who forget to pay a court fine on an old case, and in many of these situations the defendant honestly believed they had paid in full or simply forgot to pay. If the case that the warrant was issued for was not serious, judges may release the defendant on his/her own recognizance or on a small bail amount. But if the case was serious, the judge will set a higher bail amount. And if the case was very serious or if the defendant is a flight risk, the defendant may have to remain in jail pending the outcome of the court case.
If someone already knows that there is a warrant out for his/her arrest, they are encouraged to hire an attorney to try to "quash" the warrant as soon as possible. Once the warrant is recalled, the criminal case can resume without the defendant always fearing that he/she may get arrested if he/she happens to get pulled over at a traffic stop. And the longer an arrest warrant is out for someone, the less willing judges are to quash it. Read more information on Nevada bench warrants.