When an officer comes to the scene of an accident, he or she does a few standard things. 1. Secure the scene 2. Check for and treat injuries 3. Prevent fires and other crashes 4. Photograph the scene 5. Field sketch and measurements 6. Locate and interview witnesses and drivers 7. Exchange information and complete the crash report 8. Tow vehicles 9. Re-establish traffic flow as soon as possible, especially on major roads and around rush hours 10. Cite the violator
I would like to go over each of these and give what they mean.
An officer's responsibility to conduct a motor vehicle collision investigation begins at the time he or she is directed to the collision scene. It is at that precise moment that the officer should begin to obtain as much information as it is available from the radio operator, such as type of collision, location, extent of injuries, traffic condition, etc1.then the officer should at the set speed for the department procedures of running code to a scene proceed to and secure the scene. If medical attention is needed, the officer will call it in, but assuming that there is no such need, the officer’s first job is to. This is the 1st of the 10 things we as police should do. the patrol vehicle is the first available tool to use in traffic control, other devices such as plastic traffic cones and flares can also be used. They help to channel other cars away from the scene. when the first responding officer has evaluated the injuries involved and rendered medical assistance if necessary, they should begin divert cars from the scene then he should try to get the cars out of traffic as soon as possible. But he should take a few quick photos of the crash site with them untouched. Then move the cars making sure he sketch where they are for his reports later The officer will also take pictures of damage to the vehicles, . If there are skid marks leading up to the impact photos of them as well as measurements and what type they look like After completing this part the officer should start to interview both drivers separately and then any witnesses for the most important thing about any traffic accident investigation is to obtain all the relevant facts about the incident. When the officer locates the drives he should gather their licenses, and they should be kept by the officer until the investigation is completed. this safeguards against one of them possibly leaving the scene before everything is completed. One thing that helps make sure you got the right drivers and that one car did not switch is to ask each driver to point out the other driver. then the officer will try to get official statements from the drivers involved, and from any witnesses. From the testimony of the drivers and witnesses, the physical evidence at the scene of the accident, the officer’s experience in investigating accidents, and any special training that the officer has, he or she will prepare a report that details how the accident happened. This report will likely include the officer’s opinion as to the cause of the accident
After all this if the cars cannot be driven the officer should call to have them towed asking the drivers if they want him to get the company that the department uses in the area or let them call one of their own. But it should be done as soon as possible so as to restore the flow of traffic. Once all this is done and the officer has a good indication of who is at fault he should cite the party that caused the accident.

Citation
Casteel, David A, and Steven D. Moss. Basic Collision Analysis and Scene Documentation. 2nd ed. Tucson, AZ: lawyers & judges, 1999. Print.

MARTINEZ, LUIS E. TRAFFIC COLLISION INVESTIGATION MANUAL FOR PATROL OFFICERS. 2nd ed. 1994. eBook.

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Dan,
As you can see any motor vehicle accident must be treated like a crime scene until the facts of the incident are found. Again this can be complicated by Fire/EMS personnel, as well as bystanders, the time of day (rush hour)and even the weather. Establishing the perimeters and maintaining the scene is crucial. Then the facts can be gathered. As you may know any traffic accident has the potential of a liability suit (enhanced by the many commercials we see on TV from attorneys). The more training the officer has the easier it is for him or her to determine the facts, gather the evidence, and complete the report. -90%