You may move the cars out of the road so no one else is hurt.  You don't have to "preserve the scene" until the cops get there.  If anyone was hurt, or there was more than $500 of damage done to the cars, the police will make a "Crash Report."  Usually a Highway Patrol Trooper shows up.  Cooperate with the police with a statement.  Statements made to the police are generally not admissible for the civil case.  Follow up with medical care.  If you are hurt, and it was not your fault, call an attorney.   We prefer you call us, but ANY attorney is better than no attorney.   All attorneys are required to learn about personal injury in law school,  After talking to an attorney THEN you can start calling insurance companies.  You don't have to call your insurance company, or any insurance company, right away,  They can use your statement against you.  An attorney can only help you.