For years, this country’s roadways have been a recurring scene of death and destruction due to fatal car crashes. The National Highway Traffic Safety Administration estimates that about 43,000 people are killed in fatal car accidents each year in the United States.
How these fatal crashes happen is what keeps traffic investigators and trained crash reconstructionists busy every day. They must map the scene evidence to determine the likely events that may have caused the crash.
With more crowded roadways and more crashes, investigating, measuring and diagramming these scenes can pose a danger---both to anxious motorists forced to wait for a crash scene to clear, and to the investigators working the scene. Since a roadway may be shut down entirely, or, more often, with just one lane left open for traffic in both directions, it’s easy for secondary vehicle accidents to occur among drivers anxious to get moving again.
Because investigators frequently must work a cramped crash scene close to moving traffic, the potential for serious or fatal injuries is always present. The total station, which has been the predominant instrument used among crash investigators to map scenes, has proven effective for mapping scenes accurately and quickly, allowing for quicker scene clearance, making investigations safer.
Originally designed for surveyors, the total station has been conveniently adopted for use at crash scenes due to its high accuracy and ability to capture large chunks of evidence data points. Basically, a total station is an electronic/optical instrument with an electronic distance meter (EDM) for reading slope distances from the device to a particular point.
The total station can determine coordinates of an unknown point relative to a known coordinate if a direct line of sight can be established between the two points. Angles and distances are measured from the total station to points on a roadway’s crash scene. The coordinates (X,Y, and Z or northing, easting and elevation) of surveyed points in their relation to the total station’s position are calculated via trigonometry and triangulation.
Once the points are all mapped, they are then fed into a data collector connected to the total station. From there, the data can be fed into a crash scene diagramming program to create a 2D or 3D diagram.
Battery of total stations used In Las Vegas
Las Vegas, Nev., aside from its image as an entertainment and gambling mecca, has a plentiful share of car crashes. The city’s population has exploded in the last 20 years. And tourists stream into and out of town constantly. “That combination makes for a more accident-rich environment,” says Bill Redfairn, a veteran detective with the Las Vegas Metro Police Department’s (LVMPD) Fatal Crash Investigation Detail. He notes that the Detail investigates 200 to 300 serious injury or fatal car crashes a year.
This explains why LVMPD has an impressive array of total stations for investigating crashes. These range from older models to the latest in total station technology, which today includes robotic and GPS total stations.
In the 1980’s, LVMPD did not have total station technology, using, instead, tape measuring wheels and regular tape measures, and even generating crash diagrams by hand. About 15 years ago, it purchased two Nikon total stations. But batteries wore out quickly and it was hard to replace them. So, although these units are still used today, the LVMPD turned to Sokkia total stations, upgrading through the years to the newer technologies.
The LVMPD’s Fatal Crash Investigation Detail usually assigns two detectives (primary and secondary) and a sergeant to each major crash. The supervisor (primary detective) has always run the total station. Earlier total stations required two operators--one to run the total station and another to hold the prism pole over points of evidence so they can be recorded and relayed back to the total station.
Remote Control Devices Speed Up Scene Mapping