Perhaps the rash amongst us would like to know about document by the ACLU called "KNOW YOUR RIGHTS: What To Do If Questioned By Police, FBI, Customs Agents or Immagration Officers". While mostly aimed at immigrants, it contains the following advice:
Q: What if the police stop me on the street? A: Ask if you are free to go. If the answer is yes, consider just walking away. If the police say you are not under arrest, but are not free to go, then you are being detained. The police can pat down the outside of your clothing if they have reason to suspect you might be armed and dangerous. If they search any more than this, say clearly, “I do not consent to a search.” They may keep searching anyway. You do not need to answer any questions if you are detained or arrested.
Q: What if police stop me in my car? A: Keep your hands where the police can see them. You do not have to consent to a search. But if the police have probable cause to believe that you have been involved in a crime or that you have evidence of a crime in your car, your car can be searched without your consent. Clearly state that you do not consent. Officers may separate passengers and drivers from each other to question them and compare their answers, but no one has to answer any questions.
Re: Shall we slow down a bit?