If you witness a crash or is involved in one, you should:

• Notify the police and call an ambulance if there's any injury.
• Wait at the scene but try not to block traffic.
• Ask for assistance from passing motorists, bikers, or joggers, if needed.
• All of the above.
  Explanation:

  "If you witness a crash or is involved in one, you should: 1) Notify the police and call an ambulance if there's any injury. 2) Wait at the scene but try not to block traffic. 3) Ask for assistance from passing motorists, bikers, or joggers, if needed."