Cluster sites are areas or specific locations where a particular type of trauma call happens repeatedly. For example, there may be a single tree that has been hit several times and caused fatalities, or a particular curve where semi-trucks tip over. It may be a stretch of public beach where young men drown, or a residential district where auto vs. pedestrian fatalities occur to elderly people.

Any time similar, fatal events occur repeatedly at a particular location or area chances are good that you have a cluster site. When fatalities occur repeatedly under similar circumstances or within a particular population, they give clues to the root cause(s) of the fatal events. With this information, you know where the problem is, under what circumstances it occurs, and who it’s happening to. You can then begin zero in on the hazard(s) and proceed to plan the best strategy to eliminate the problem.

The different features and uses of an area determine the types of hazards that will exist there. Increased speed is a contributing factor in the severity of all types of motor vehicle crashes. Fatality rates for auto vs. pedestrian crashes at 55 mph or more are nine times higher than they are for crashes that occur at 30 mph or less. A residential district where young people play or walk adjacent to an unlighted highway has an increased potential for nighttime auto vs. pedestrian fatalities. A downhill slope with a sharp curve and narrow shoulders will cause a higher incidence of roll over and run off road crashes. A two lane highway with uncontrolled intersections or driveway entrances along the roadway increase the chances for rear end, turning, or broadside auto vs. auto collisions. Unprotected bodies of water along the road increase the chances of submerged vehicle entrapments. Cigarette smoking in the home is the greatest single risk factor for fatal house fires and results in a 28% increase in death. Residences with wood heat are approximately 15% more likely to have fatal house fires. It’s not surprising that rural America, which has all these issues, has an increased per-capita incidence of traumatic fatality.

Clusters of motor vehicle fatalities: In most communities, there are a few identifiable areas of the roads that are over-represented for crashes of a particular type and severity. Commonly known as "Dead man’s curve", or "Blood alley" these are areas that have some feature that is causing people to lose control of their vehicles more often than elsewhere on the same road, or that increases the lethality of any crash that occurs there. The reasons for this may be as simple as inadequate signage or lighting, a deceptively sharp turn following a long straight stretch, or a tree immediately adjacent to a curve. For whatever reason, certain parts of the roadway are much more likely to cause a fatal crash than the rest of the road.

Responding to more than one fatality at the same site under similar conditions is often the first tip off. Think back over the fatal car crashes you’ve been on. Are there any that recur at a particular location? Ask your crewmembers if they can think of any. Often it’s easy to identify cluster sites before going back through the records to confirm them. If you’ve been around the area for a while, you probably already know of at least one. When an emergency worker has been to two or three fatal incidents at one particular spot, and when the same scenario is present each time, it’s not hard to identify a cluster site. None of this is rocket science, it’s very simple to gather the records together for a known cluster site, investigate the events and find the one factor that can be modified or removed that will protect the entire population at risk. The only requirements are accuracy, completeness, and matching your data set with at least one other to confirm the findings.

Emergency responders are in a unique position to know where these dangerous areas are and the types of incidents that happen there. We also understand the cost in human suffering and grief caused by them. Because of this, EMTs are the perfect people to call these hazards to the attention of the agencies responsible, in order to get them eliminated. We have the specifics, and we also understand the reality of leaving things as they are. That is not the kind of knowledge you get from books.

Even before the incidents occurred, and before we gathered any data on OTBs we knew where they were likely to happen (Local highways at OTB cluster sites: Steep, high bluff areas with very little or no shoulders protected by ineffective log barriers) to whom (local highway users) and when (first rains). OTBs were such a common occurrence that when the first rains came, we would call in extra personnel, run a thorough check out and maintain all the rescue gear, train on OTB scenarios, and wait anxiously for the calls to come. They usually did. We were quite good at quickly accessing and bringing the patients up the bank. Even when they were unstable and required advanced life support before rescue, we could run a full code on the patient at the bottom of the embankment, secure them in the stokes litter, and bring them up the cliff on a winch cable over 300 feet in less than an hour utilizing a total of three or four personnel to do it. Nevertheless, the efficient and aggressive EMS didn’t often save anyone’s life. Multiple system trauma and massive internal injuries were common and usually too severe to withstand transport times in excess of an hour.

Obviously we weren’t the first people to figure out where fatal OTBs were happening. The old log barriers were along the roadway precisely at most of the cluster sites we identified. At one time, the large fir logs served as effective barriers to vehicles leaving the roadway, but by the late 70’s they’d rotted down to a thickness of less than a foot in many places. This is one good reason that ongoing surveillance is so important; things change.

In 1983 I documented six OTB fatality cluster-sites; most were obvious (as some of yours probably are). These six sites accounted for almost all of our fatal Over-the-Bank crashes. In 1985, a total of one-half mile of custom designed guardrail was installed by the California Department of Transportation at those sites. (There was a problem with installation at most sites because they were so steep and narrow that there was no shoulder to anchor guardrails to.) In 1984, engineers in Eureka, California Dept. of Transportation developed a new guardrail system specifically for this problem. They later received an award for engineering excellence for this innovative design. (This new guardrail system was anchored on steel beams buried in trenches deep beneath the roadbed and cantilevered out to the edge.) As soon as the guardrails were in place, our Over-the-Bank, and multiple fatality problems disappeared.

That was 17 years ago. In 1996 I re-evaluated the effectiveness of the guardrail system by looking at all the fatalities from OTB crashes from the year 1977, (when I first started working in Willow Creek and Hoopa), until 1985, (the year the guardrails were installed). I compared the OTB fatalities that occurred from 1977-1985 to the OTB fatalities that occurred from 1986 to 1996 (after the installation). I was interested to find the difference in the incidence of deaths. I also was concerned that by keeping people on the roads instead of allowing them to go Over-the-Bank, there would be an increased incidence of fatalities from hitting the rails themselves, or perhaps form bouncing back across the center-line and hitting other vehicles.

Statistically, without improvement, approximately 26 people would have died in Over-the-Banks at those six sites within 10 years. Instead there were zero OTB fatalities at those sites.

Happily, there were also zero fatal auto vs. auto crashes involving vehicles that were kept on the roadway by the guardrails, and zero fatalities as a result of vehicles hitting the guardrails themselves. In addition, there were only two multiple fatality crashes in the entire ten-year period with a total of four people killed. One of these was near an improved site but the fatality was coincidental; the protections were not involved in any way. The other was far from any cluster site.