Albert Masetti & Associates,  Consulting Engineers


November 2000


  • Editorial Note
  • Rules for Rumble Strips
  • How the Brain Works

Editorial Note

In the last issue (September 1998), I talked about drivers' perceptions, human factors issues, communications, structure of language, use and misuse of language, and ergonomics. With this issue, we carry on with rules for rumble strips and further aspects of how the brain works.

Masetti's Rumble Strip Rules

Every state and operating authority has its own idea. In the U.S. alone there may be 100 different designs for rumble strips. It's more art than science. Some rumble strips are edge devices to alert drowsy drivers. The summary reflections below are for the main line:

1. Based on an Israeli study, the distance from first strip to the "objective" (stop sign, curve, etc.) seemed to have an optimum length of around 350 to 550 feet. The study had 38 strips, but the spacing wasn't stated in the synopsis. The "optimality" was based on the largest incremental percentage of speed reduction taken throughout the entire length to the test area which was 800+ feet.

2. Elapsed times to pass through each segment should be equal or be perceived as equal. This is based on the study of the Osaka Markings.

3. Unequal ("logarithmic") spacing between rumble bars produces different sounds. This is based on observations of the three sets of rumble strips on the exit ramps from I-280 into Newark, N.J. Wide spacing produces a deep sound; medium spacing produces a "medium" sound; and narrow spacing produces a high-pitched sound.

Rumble strips get drivers' attention; they do not change behavior or cause cars and trucks to slow down. Therefore, there must be warning signs ("nanny signs") with flashing lights to tell drivers what to do. Aggressive rumble strips may serve as traffic calmers if each set has 10 to 20 bars.

4. "Modular spacing" of rumble bars within rumble strips should be about 25 inches (if designed for trucks), which is the width of a manhole cover. It was observed while riding in the cab of an 18-wheeler that "normal" rumble strips are not particularly felt or heard by truck drivers because of vehicle suspension, competing noises or vibrations and other sensory inputs. But, every time the truck went over a manhole cover, the cab jounced. We measured the flat spot on the bottom of a truck tire at 16 inches; the manhole cover at 25 inches. So bars can be spaced at 25", 38", 50". Car "modules" can be smaller.

5. Rumble strips can be grooved or raised. Raised rumble strips can be made of asphalt or thermoplastic. It takes about six 1/8" lifts of thermoplastic to get 1/2" thickness. If a large number of strips is used, then 1/4" thickness may work for cars; 3/8" for trucks. Start thinner and build up with experience. Aggressive, hard edges work better than ramped-up edges.

6. Annual touch-ups may be necessary due to wear, compression, snow plowing, etc. As strips get thinner, vehicle speeds seem to increase. Experimentation is necessary.

Much of the above is based on personal experience. NCHRP Synthesis 191 "Use of Rumble Strips to Enhance Safety" is helpful. Osaka Markings are somewhat covered in the "Review of Two Innovative Pavement Patterns that Have Been Developed to Reduce Traffic Speeds and Crashes" published by the AAA Foundation for Traffic Safety.

How the Brain Works

One intriguing aspect of how the brain works is how trauma and extreme stress are processed internally. Once an event is over, it may continue as a too-vivid memory, resulting in what we now call Post Traumatic Stress Disorder (PTSD).

Eyes This short article discusses PTSD and two eye movement techniques that can cure it: Eye Movement Integration (EMI) and Eye Movement Desensitization and Reprocessing (EMDR).

These techniques work, although some people question how. It is possible that patterns of thought are interrupted, as described in the theories of Neuro Linguistic Programming (NLP). But the best attempt at an explanation so far is that the eye movement therapies are similar to REM sleep eye movements, which apparently trigger the filing of data accumulated during the day in appropriate places in the brain. If the filing does not take place, the data cycles over and over in short-term memory, like churning in computer multi-tasking. The continuous recycling process may be similar to flashbacks.

The EMI approach was developed by Robert Dilts and Steve Andreas and is taught by Ron Klein in Silver Spring, Md. (301-565-0103). EMI works by using a variety of slow, smooth, comfortable hand/eye movements - horizontal, circular, and diagonal, etc. Any harshness from the original situation is depotentiated by removing the client from the event by imagining it takes place on a movie screen with the client seeing it from the rear of the theater while also seeing him/herself watching it in the front row. This dissociation is also known as the "movie theater metaphor." There are also safety anchors available to protect the client from adversely reacting, so that the PTSD relief can proceed smoothly.

EMI can also be done without the safety procedures, but if the client is fragile or begins to react adversely (usually indicated by some moisture or film on the eye or some facial changes), the procedure can be stopped and the safeties utilized before resuming. The use of these physiological cues is something that Klein includes as an integral part of his training.

The EMDR approach was developed and is taught by Francine Shapiro, Ph.D. (831-372-3900 or and has also been very successful with Vietnam veterans or anyone suffering from traumatic stress. The EMDR technique is performed in the associated state exclusively, which means the person relives the events and experiences all of the pain again. EMDR hand movements are rapid and the therapist must be skilled enough to deal with abreactions that may develop.

Training on both these techniques is relatively straight forward. EMI training is one day. The two levels of EMDR training are three days each. Some previous counseling background training or experience would be useful.

Other thoughts:

The therapist does not need to know any of the specific details of any stress-producing, embarrassing or traumatic event. No need for deep probing or questioning, although the therapist needs to know, for example, and be prepared that if the client's complaint is about claustrophobia, there may have been a related childhood trauma.

The techniques are flexible and can be used directively (PTSD or phobias), generally (free-floating anxiety or depression), over the phone, or with blind people (using sounds, etc.), and typically in as few as one to four sessions.

Two other techniques for another time: Thought Field Therapy (760-564-1008) and Rapid Eye Technology (503-399-1181).

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