Apparatus color safety research questionable
L. Charles Smeby, Jr.
Marshfield, Massachusetts
After reading the summary in News in Brief (February 1996) about the article in the Spring 1995 issue of Journal of Safety Research by Solomon and King, entitled “Influence of Color on Fire Vehicle Accidents,” I would like to comment on the validity of the results. To begin with, the authors state that, “Since the number of accidents [in the study] is small, accurate estimation of probability by vehicle color is suspect.” My first question was, Why would you publish a summary of an article that the authors admit is probably not accurate?
Normally, the smaller the number of observations, the greater the possibility the observations could be influenced by chance or random effects. Generally, most statistical studies need about 250 independent observations to be reliable. This study had only 20!
In addition, in statistical studies, a researcher will attempt to normalize the data or use special techniques such as multiple linear regression when more than one independent variable may be present. For example, the data set contains 16 accidents where “lights/sirens” were activated. For a “visibility study,” you could easily argue that emergency lights are just as likely to cause other drivers to identify or become aware of the fire vehicle. Therefore, you would want to remove any possible influence on the study and eliminate all observations with “lights/sirens.” That would leave only four accidents that could have possibly been prevented by the “color.”
On the issue of visibility during emergency responses, field studies at the Fire Department Instructors Conference, Cincinnati, Ohio, in 1992 indicated that presently required “warning lights” were inadequate for day use and barely adequate at night (“Improving Apparatus Electrical Systems,” Fire Engineering, February 1996). In response to these studies, the National Fire Protection Association`s Fire Department Equipment Committee has proposed substantial upgrading of emergency lighting systems to improve the visibility of the fire apparatus. This is one way to improve the ability of other drivers to become aware of the presence of an emergency vehicle.
Another study by the St. Louis (MO) Fire Department reported a substantial reduction of accidents after having switched from lime-green to red in 1987. I would not conclude that this had anything to do with the reduction, however, because other changes occurred during this same period of time. This department made several changes that probably directly account for the improved accident rates. For example, members no longer respond with lights and siren to many calls, drivers must come to a complete stop at stop signs and red lights, and the department has reemphasized defensive driving techniques.
One more comment about normalizing data. Any accidents where the fire vehicle ran into the other vehicle should have been removed. In other vehicle visibility studies, accidents where the vehicle was struck on the side or back were the only ones used. The authors did not mention removing accidents where the fire department driver could be at fault.
Finally, if lime-yellow is truly a better safety color, why didn`t the authors recommend this color for stop signals on traffic lights or brake lights on cars? How many drivers do you think would give the “right-of-way” to an emergency vehicle with lime-yellow emergency lights?
