Traffic Accidents Mapped Electronically

New technology is helping gather traffic accident and crime scene data quickly and accurately.

by / January 31, 1996
PROBLEM/SITUATION: Traditional methods of gathering evidence at scenes of serious highway accidents contribute to traffic congestion and delays.
SOLUTION: Modified surveying systems capable of electronically measuring, recording, and generating data faster, more accurately, and in less time than it takes using traditional methods.
JURISDICTION: Kentucky State Patrol; Minnesota State Patrol; city of Stockton, Calif., Police; Kalamazoo County, Mich., Prosecutor's Office; Lexington County, Ky.
VENDORS: MJC & Associates; Sokkia Instruments.
CONTACT: Mike Capman, president, MJC & Associates, 823 Parchmount Ave., Kalamazoo, Mich. 49004-1738. 616/344-3575.

A multi-car collision involving fatalities turns an interstate highway into a parking lot for hours, sometimes days. Much of the delay results from the necessity of collecting legal evidence relating to the accident, a process known as forensic mapping. It usually involves sketching vehicle and body positions, measuring the length and direction of skid marks, diagramming elevations, intersections, curves, and the natural and constructed features of the immediate area. With conventional tools -- pad and pencil, 100-foot steel tape and measuring wheel -- the process is tedious, limited in accuracy and scope, and painstakingly slow.

Lt. Robert Miller of the Kentucky State Patrol explained that the cost of traffic delays resulting from post-accident investigations can be substantial. "The federal government figures that while the police are gathering evidence and reconstructing an accident scene, delays are costing taxpayers $8 per vehicle for every hour traffic is stalled. Another study shows that commercial truck operators lose $1 a minute sitting in traffic. In northern Kentucky, up around the greater Cincinnati area, more than 16,000 vehicles an hour go through one stretch of I-475. If we have to shut it down eight to 10 hours for an accident involving several vehicles, we are talking about astronomical numbers."

Since hand-drawn maps and diagrams made at the scene are, by necessity, rough and hurried, an officer will most likely spend time at the station redoing them with ruler and compass to make them more presentable to the courts. The officer's time, Miller believes, would be better spent patrolling the highway.

In response to the need for faster, more accurate methods of gathering evidence, some law enforcement agencies and investigators have begun using a modified version of a surveyor's "total station," a system capable of electronically measuring and recording distances, angles, elevations, and the names and features of objects. Data from the system can be downloaded into a computer for display or printed out on a plotter. In negligent homicide and vehicular manslaughter cases requiring reconstruction of the crime scene, some courts now prefer the precision, scope and professional appearance of exhibits collected and generated by the electronic system.


There are basically four components of the forensic mapping system: a base station, prism, data collector and tripod. The prism, positioned at a desired spot, reflects an infrared beam back to the tripod-mounted base station, where a microprocessor automatically calculates distance, height and angle, and sends the information to the data collector. To identify the locations, features and objects being measured, the user selects codes from the data collector's built-in library. Measurements are referenced to geographic coordinates by positioning the base station over a known point, such as a manhole cover, fire hydrant or surveyor's brass monument.

The data collector is later downloaded into a PC, running software that translates the file into language used by a simplified CAD program. Other software allows the operator to put in titles and legends and identify all types of objects -- trees, buildings, vehicles, bodies, blood, guns, etc. -- with appropriate symbols. The result is a comprehensive map that can be scaled to any size and displayed or printed out on a plotter. When integrated with GIS and GPS, forensic data may assist state engineers and investigators in pinpointing high accident locations and tracking crime trends, respectively.

"We currently use Sokkia Total Stations and MAP software," Lt. Miller said. "We also have laptops because troopers are often 75 miles or more from their base, so they use the laptops in their cars to type up reports, visually check the completion of maps, and see that nothing critical is missing. We don't want them to drive back to their base and find out a drawing is incomplete, then have to drive all the way back again, just to get the information."

According to Lt. Miller, high-tech forensic mapping is saving Kentucky considerable funds. "Before we had this equipment, we had troopers spending eight to 10 hours making scale drawings of accident scenes where there were curves and lots of intersections. Now, they go out and get measurements in an hour or so, push a button and the lines are drawn for them in real-world scale. Instead of sitting at a desk for hours drawing, they can be back on the road patrolling."

Miller cited a study by the University of Kentucky, for the Transportation Research Commission, showing that electronic methods enable officers to get 40 percent more measurements at accident scenes in about 40 percent of the time it generally took using conventional methods. "We don't have to shut down the road system quite as long or so often following an accident," Miller said. "With this technology, we can just raise the prism pole up and get our measurements across traffic while it's moving -- at least with one lane open. That also means more accurate and professionally produced exhibits for the courts and juries."

Miller pointed out that the system is equally effective in mapping crime scenes. "If there is a murder scene, we call troopers to go over there and do the mapping for the detectives. They'll set up inside a warehouse or wherever the crime scene is. We've used it inside buildings as well as outside; the principles are the same. If
we need to look at bullet-hole trajectories or blood spatter that may be on a wall or window, we take vertical measurements and map the side of the building. If a vehicle goes off a bridge, or somebody jumps off, we can take the measurements, put them in a CAD program and
get a scale drawing of the
bridge face."

David DeBack, assistant prosecuting attorney for Kalamazoo County, Mich., appreciates the fact that high-tech forensic mapping provides so much more information. At the same time, he cautions that the amount of detail the system can generate is almost overwhelming. "If you're going to be using this kind of information, you have to make sure you're working closely with your expert so that you don't overlook something in that stack of data. There is more information than ever at your disposal, and you really have to have good control of it, or else I'm sure it could overwhelm a jury if you laid all of it out."

DeBack stressed that a final report from an officer or accident reconstructionist "should include a synopsis of all the data gathered and generated, then focus you in on the individual aspects that are being relied on."

Anticipating the integration of forensic mapping with GIS and GPS, Miller said Kentucky's accident investigation report is currently being revised to include latitude and longitude. Forensic maps referenced to previously surveyed points can be put into a GIS database and overlaid onto a basemap of streets and highways. The combined technologies can provide pinpoint locations of crime and accident scenes. "We're already using this system for marijuana eradication," Miller added. "I'm sure it won't be long before we use it to pinpoint accidents."

Mike Capman, a consultant who trains law enforcement agencies in the use of a forensic mapping system, said the operation is relatively simple and can be done by one person. He acknowledges, however, that at first, some of the trainees are intimidated by the system. "So I start out by showing them how a picture can be made by connecting dots with lines. I say if you can understand that, you can understand the process of the software, because this whole thing just connects lines, dots and symbols. It puts a dot or a symbol where a gun has been found, or draws a manhole cover or a fire hydrant. Once they see that, it's pretty simple."

Capman's 32-hour program has been certified by several states. He is quick to point out that forensic mapping does not tread on surveyors' turf. "We are very careful to make the distinction in our training between a surveyor's objectives and what our needs are for scene investigation."

Lt. Miller echoed this distinction. "We don't do boundaries, we don't try to close lines, we don't plot houses for deeds. The only thing we do is electronically map a small section of ground where an accident or crime occurred."

Capman said there is one drawback to the system -- it cannot be used in heavy rain or snow. Perhaps this is a point to consider, given that many accidents occur in these conditions.

State and local law enforcement agencies have tapped a variety of funding sources to pay for forensic mapping systems, generally costing around $14,000. The Intermodal Surface Transportation Efficiency Act (ISTEA) makes grants available for traffic congestion management, through the Department of Transportation's Highway Safety Division. The Minnesota State Police funded their systems with a grant from the Commerce Department's National Highway Traffic Safety Administration. In Stockton, Calif., the city police department financed a mapping system through a combination of funds from the city budget and drug forfeiture money.

Money for mapping systems used by the Kentucky State Patrol came through a joint grant from Lexington County and the Kentucky State Police. "We got the grant," Miller explained, "because we were able to successfully convince the national transportation people that if we had this equipment, we could cut down on traffic congestion resulting from accidents, and get more information, more accurately, and in less time than we could using the traditional 100-foot steel tapes."